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Editor Work2017 Vol. 25, No. 2
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2017, 25(2): 257-276.
Abstract
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From October 13 to 21, 2016, the 10th National Engineering Geological Conference is successfully held in Chengdu, Sichuan Province. In the opening ceremony, the author delivered a keynote presentation entitled "Engineering Geology: Review and Prospect of Past Ten Years". The author was the Chairman of the Eighth and Ninth Engineering Geology Committee. So this paper is his work review over past ten years. The author sums up with three phrases for the development of Engineering Geology in China over past ten years. They are a) Founding super engineering projects, b) Protecting people's well-being, c) Promoting the development of academic disciplines. Over the past ten years, Engineering Geology in China closely integrated with the national strategic demands and scientific and technical problems in engineering, provided the technical supports for the national super project construction, greatly reduced the death toll caused by the geological disasters through the theoretical innovation and the technological development, and made a large number of representative theoretical and technological results. The author also expresses his great expectation that China's Engineering Geology will reach the world's top level.
From October 13 to 21, 2016, the 10th National Engineering Geological Conference is successfully held in Chengdu, Sichuan Province. In the opening ceremony, the author delivered a keynote presentation entitled "Engineering Geology: Review and Prospect of Past Ten Years". The author was the Chairman of the Eighth and Ninth Engineering Geology Committee. So this paper is his work review over past ten years. The author sums up with three phrases for the development of Engineering Geology in China over past ten years. They are a) Founding super engineering projects, b) Protecting people's well-being, c) Promoting the development of academic disciplines. Over the past ten years, Engineering Geology in China closely integrated with the national strategic demands and scientific and technical problems in engineering, provided the technical supports for the national super project construction, greatly reduced the death toll caused by the geological disasters through the theoretical innovation and the technological development, and made a large number of representative theoretical and technological results. The author also expresses his great expectation that China's Engineering Geology will reach the world's top level.
2017, 25(2): 277-283.
Shear strength of saturated MSWI bottom ash increases with age due to its activity. In this paper, shear strength of saturated MSWI bottom ash is measured using triaxial tests. The confining pressures are 50kPa, 100kPa, 200kPa and 400kPa, respectively. The dry densities of tested samples of saturated MSWI bottom ash are 1.4g·cm-3, 1.5g·cm-3and 1.6g·cm-3.Their ages are 3d, 7d, 14d and 28d, respectively. The results of triaxial tests show that the failure modes of saturated MSWI bottom ash in triaxial tests are affected by cured ages and confining pressures. The samples with age less than 14d undergo brittle failure at confining pressure less 200kPa. The envelope of Mohr-Coulomb criterion is not a straight line. Two straight lines exist in the plane of σ1-σ3 at demarcation point of σ3=200kPa. Thus, the regressing maximum principal stress with minor principal stress is suitable to estimate shear strength parameters using triaxial tests.
Shear strength of saturated MSWI bottom ash increases with age due to its activity. In this paper, shear strength of saturated MSWI bottom ash is measured using triaxial tests. The confining pressures are 50kPa, 100kPa, 200kPa and 400kPa, respectively. The dry densities of tested samples of saturated MSWI bottom ash are 1.4g·cm-3, 1.5g·cm-3and 1.6g·cm-3.Their ages are 3d, 7d, 14d and 28d, respectively. The results of triaxial tests show that the failure modes of saturated MSWI bottom ash in triaxial tests are affected by cured ages and confining pressures. The samples with age less than 14d undergo brittle failure at confining pressure less 200kPa. The envelope of Mohr-Coulomb criterion is not a straight line. Two straight lines exist in the plane of σ1-σ3 at demarcation point of σ3=200kPa. Thus, the regressing maximum principal stress with minor principal stress is suitable to estimate shear strength parameters using triaxial tests.
2017, 25(2): 284-291.
The soft dredger fill has the characteristic of large void ratio, strong compressibility and low strength. It is fine grain soil of high clay content. Although the short soil formation time, it has certain structure strength. Mechanical property of soil depends on soil's microstructure. In engineering practice, the structural strength of soil increases in the stage of safe operation because of the sustained pressure on the soft dredger fill that has ground treatment. To study the microscopic parameter evolution of soft dredger fill in the process of hyperplasia, the remoulded soil from Binhai New Area of Tianjin is used to be the test material of complete structural deterioration. The variation of grain and pore count, equivalent diameter and aspect ratio is analyzed quantitatively in the process of hyperplasia of structure strength with Scanning Electron Microscope. The result of tests shows that: in the process of hyperplasia of structure strength, the count of grain and pore and equivalent diameter decline, while aspect ratio of grain and pore, and equivalent diameter increase. The change is obvious at the beginning of the generation of structure strength. The longer consolidation time, the stronger constitutive property is. Deviator pressure and consolidation time have the same effect on the constitutive property of soil.
The soft dredger fill has the characteristic of large void ratio, strong compressibility and low strength. It is fine grain soil of high clay content. Although the short soil formation time, it has certain structure strength. Mechanical property of soil depends on soil's microstructure. In engineering practice, the structural strength of soil increases in the stage of safe operation because of the sustained pressure on the soft dredger fill that has ground treatment. To study the microscopic parameter evolution of soft dredger fill in the process of hyperplasia, the remoulded soil from Binhai New Area of Tianjin is used to be the test material of complete structural deterioration. The variation of grain and pore count, equivalent diameter and aspect ratio is analyzed quantitatively in the process of hyperplasia of structure strength with Scanning Electron Microscope. The result of tests shows that: in the process of hyperplasia of structure strength, the count of grain and pore and equivalent diameter decline, while aspect ratio of grain and pore, and equivalent diameter increase. The change is obvious at the beginning of the generation of structure strength. The longer consolidation time, the stronger constitutive property is. Deviator pressure and consolidation time have the same effect on the constitutive property of soil.
2017, 25(2): 292-299.
The influence of freeze-thaw action on the permeability of undisturbed and remolded Q3 loess in Xi'an city is comparatively studied by the SEM and triaxial consolidation permeability tests. The experimental data indicates that the microstructure of undisturbed and remolded loess all changes significantly under freezing-thawing condition. The soil cementation structure is weakened, and then the particle alignment becomes more loose. Finally, the void ratio of soil increases and makes the permeability enhanced. Freezing-thawing makes the surface structure of undisturbed and remolded loess destroyed greatly, and has a bigger influence on the undisturbed loess. The cracks produced by freezing-thawing process become the main channel for water flow and migration, resulting in the obvious increase of permeability for undisturbed and remolded loess. With the increment of water content, the permeability coefficients for undisturbed and remolded loess all firstly increase and then decrease under freeze-thaw cycle condition, complying with the parabola law. With the increase of freezing-thawing times, the permeability coefficients all firstly increase and finally approach to a steady state, following the exponential rule. With the increment of cell pressure, the permeability coefficients all firstly decrease and finally reach a steady state, also following the exponential rule. The permeability of undisturbed loess is always greater than that of remolded loess under the same condition. Moreover, the permeability coefficient difference between undisturbed and remolded loess is smaller with the increase of cell pressure.
The influence of freeze-thaw action on the permeability of undisturbed and remolded Q3 loess in Xi'an city is comparatively studied by the SEM and triaxial consolidation permeability tests. The experimental data indicates that the microstructure of undisturbed and remolded loess all changes significantly under freezing-thawing condition. The soil cementation structure is weakened, and then the particle alignment becomes more loose. Finally, the void ratio of soil increases and makes the permeability enhanced. Freezing-thawing makes the surface structure of undisturbed and remolded loess destroyed greatly, and has a bigger influence on the undisturbed loess. The cracks produced by freezing-thawing process become the main channel for water flow and migration, resulting in the obvious increase of permeability for undisturbed and remolded loess. With the increment of water content, the permeability coefficients for undisturbed and remolded loess all firstly increase and then decrease under freeze-thaw cycle condition, complying with the parabola law. With the increase of freezing-thawing times, the permeability coefficients all firstly increase and finally approach to a steady state, following the exponential rule. With the increment of cell pressure, the permeability coefficients all firstly decrease and finally reach a steady state, also following the exponential rule. The permeability of undisturbed loess is always greater than that of remolded loess under the same condition. Moreover, the permeability coefficient difference between undisturbed and remolded loess is smaller with the increase of cell pressure.
2017, 25(2): 300-307.
The settlement of the ground surface is one of the most concerned engineering problems in subway shield tunneling, because the settlement is in relation to the usual operation of adjacent structures and the normal proceeding of shield construction. Therefore, this paper takes the ground surface settlement as the key objective to decide the shield parameters. The parameters affecting the surface settlement are simplified into two indices, namely support pressure ratio on the tunnel face to the earth pressure and the elastic modulus of generation layer. Taking the section from Nanmenkou to Houjiatang along Line 1 of Changsha Metro as an example, this paper carries out FLAC3D numerical simulation to analyze the effects of the two indices on surface subsidence. The suggestion of the shield parameter values for the selected section of Changsha subway is then put forward. Besides, the subsiding area and the maximum of the subsidence are also proposed. This research brings out a reference for the subsequent construction of Changsha metro and provides a method for parameter deciding of shield tunneling in other cities.
The settlement of the ground surface is one of the most concerned engineering problems in subway shield tunneling, because the settlement is in relation to the usual operation of adjacent structures and the normal proceeding of shield construction. Therefore, this paper takes the ground surface settlement as the key objective to decide the shield parameters. The parameters affecting the surface settlement are simplified into two indices, namely support pressure ratio on the tunnel face to the earth pressure and the elastic modulus of generation layer. Taking the section from Nanmenkou to Houjiatang along Line 1 of Changsha Metro as an example, this paper carries out FLAC3D numerical simulation to analyze the effects of the two indices on surface subsidence. The suggestion of the shield parameter values for the selected section of Changsha subway is then put forward. Besides, the subsiding area and the maximum of the subsidence are also proposed. This research brings out a reference for the subsequent construction of Changsha metro and provides a method for parameter deciding of shield tunneling in other cities.
2017, 25(2): 308-316.
As the development activities of human underground space goes to deep earth, the high geostress has become one of the typical geological characteristics of underground rock mass engineering and has an important effect on the safety and stability of surrounding rock mass. In this paper, the distribution regularities of geostress field in our country are firstly analyzed. And then, the damage of surrounding rock mass induced by quasi-static unloading and transient unloading of geostress is studied by the methods of theoretical calculation and numerical simulation. At last, according to the testing results of damage in surrounding rock mass in Canada URL underground laboratory and diversion tunnels of Jinping Ⅱ hydropower station, the influence of unloading way of geostress on the damage formation of surrounding rock mass is analyzed. Results show that comparing with quasi-static unloading of geostress, transient unloading of geostress can produce an extra dynamic stress in surrounding rock mass and enlarge the unloading effect in radial and loading effect in tangent, which makes the surrounding rock mass easier to damage. In addition, the increase of lateral pressure coefficient can increase the damage range of surrounding rock mass induced by quasi-static unloading and transient unloading of geostress augments. In the direction of minimum principal stress, the main damage form of surrounding rock mass is shear failure. While in the direction of maximum principal stress, it shows as tension failure.
As the development activities of human underground space goes to deep earth, the high geostress has become one of the typical geological characteristics of underground rock mass engineering and has an important effect on the safety and stability of surrounding rock mass. In this paper, the distribution regularities of geostress field in our country are firstly analyzed. And then, the damage of surrounding rock mass induced by quasi-static unloading and transient unloading of geostress is studied by the methods of theoretical calculation and numerical simulation. At last, according to the testing results of damage in surrounding rock mass in Canada URL underground laboratory and diversion tunnels of Jinping Ⅱ hydropower station, the influence of unloading way of geostress on the damage formation of surrounding rock mass is analyzed. Results show that comparing with quasi-static unloading of geostress, transient unloading of geostress can produce an extra dynamic stress in surrounding rock mass and enlarge the unloading effect in radial and loading effect in tangent, which makes the surrounding rock mass easier to damage. In addition, the increase of lateral pressure coefficient can increase the damage range of surrounding rock mass induced by quasi-static unloading and transient unloading of geostress augments. In the direction of minimum principal stress, the main damage form of surrounding rock mass is shear failure. While in the direction of maximum principal stress, it shows as tension failure.
2017, 25(2): 317-321.
In order to research the influence of the shale content on road application properties of Xigeda Soil mixed filling, heavy tamping test, compression test without lateral confinement, CBR and compression strength resilience test are performed. The research result indicates the following. The optimum moisture content and maximum dry density of mixed filling are mainly determined by the content of argillaceous siltstone, in addition to the effects of the particle size of shale, the water content and the shale content. The compaction results of artificial Xigeda Soil mixed filling and actual natural random mixed filling have obvious difference. The optimum moisture content and maximum dry density of mixed filling should carry on the dynamic values, based on the content of shale, content of water, compaction degree and content of massive shale of mixed filling in the practical engineering. When shale content (mass fraction) is lower than 65%, the unconfined compressive strength of mixed filling increases with shale content linearly. The unconfined compressive strength of mixed filling decreases with shale content linearly when shale content is larger than 65%.Compression strength resilience value of mixed filling increases with shale content. Through polynomial regressive analysis between shale content and CBR value, the polynomial regressive function of CBR value of mixed filling and shale content is established with good relevance.
In order to research the influence of the shale content on road application properties of Xigeda Soil mixed filling, heavy tamping test, compression test without lateral confinement, CBR and compression strength resilience test are performed. The research result indicates the following. The optimum moisture content and maximum dry density of mixed filling are mainly determined by the content of argillaceous siltstone, in addition to the effects of the particle size of shale, the water content and the shale content. The compaction results of artificial Xigeda Soil mixed filling and actual natural random mixed filling have obvious difference. The optimum moisture content and maximum dry density of mixed filling should carry on the dynamic values, based on the content of shale, content of water, compaction degree and content of massive shale of mixed filling in the practical engineering. When shale content (mass fraction) is lower than 65%, the unconfined compressive strength of mixed filling increases with shale content linearly. The unconfined compressive strength of mixed filling decreases with shale content linearly when shale content is larger than 65%.Compression strength resilience value of mixed filling increases with shale content. Through polynomial regressive analysis between shale content and CBR value, the polynomial regressive function of CBR value of mixed filling and shale content is established with good relevance.
2017, 25(2): 322-329.
Rock bridges with different shapes, connectivity rates and arrangements, play a decisive role during slope stability evaluation. Indoor direct shear test combined with the characteristic parameters of acoustic emission is carried out. The test results reveal the failure law of rock mass containing intermittent joints with different connectivity rates and different normal stress states.The results show that: under the condition of direct shear, with the changes of normal stress and connectivity rate, failure surfaces of rock mass appear as "A-line-shaped", "X-shaped", "serration-shaped", "Z-shaped" and their combinations, which are somewhat smooth. The crack coalescences of rock mass resulting in failure happen at the same time. When normal stress is constant, with the increase of connectivity rate in intermittent rock bridges, AE cumulative counts grow linearly, while the peak value of AE counts increases generally. When the connectivity rate is constant, with the improvement of normal stress, the peak values of AE counts and AE cumulative counts both reach their peaks under the middle normal stress. Study on the failure and deformation characteristics of rock bridges with intermittent joints is not only useful to the analysis of the mechanical properties of rock mass, but also is good to the evaluation and prediction in slope engineering.
Rock bridges with different shapes, connectivity rates and arrangements, play a decisive role during slope stability evaluation. Indoor direct shear test combined with the characteristic parameters of acoustic emission is carried out. The test results reveal the failure law of rock mass containing intermittent joints with different connectivity rates and different normal stress states.The results show that: under the condition of direct shear, with the changes of normal stress and connectivity rate, failure surfaces of rock mass appear as "A-line-shaped", "X-shaped", "serration-shaped", "Z-shaped" and their combinations, which are somewhat smooth. The crack coalescences of rock mass resulting in failure happen at the same time. When normal stress is constant, with the increase of connectivity rate in intermittent rock bridges, AE cumulative counts grow linearly, while the peak value of AE counts increases generally. When the connectivity rate is constant, with the improvement of normal stress, the peak values of AE counts and AE cumulative counts both reach their peaks under the middle normal stress. Study on the failure and deformation characteristics of rock bridges with intermittent joints is not only useful to the analysis of the mechanical properties of rock mass, but also is good to the evaluation and prediction in slope engineering.
2017, 25(2): 330-335.
Water plays a pivotal role in influencing collapsible loess foundation. In this article, the physical and mechanical parameters of loess and lime soil in Lanzhou are obtained through indoor geotechnical test. The effect of different structures to control lateral seepage in subgrade loess soil is studied through indoor model test. At the same time, the settlement of roadbed is monitored. The experimental results reveal that the permeability coefficient of the lime soil is much less than the coefficient of permeability of loess. After processed by lime-soil compaction pile and lime-soil impervious wall, the moisture content of loess is far less than the value that the lateral seepage control processing is not made. Collapsibility deformation of subgrade is obviously improved. The effect of lime-soil impervious wall is better than the lime-soil compaction pile. The test results can guide the collapsible loess subgrade seepage prevention effectively, and provide a new idea for collapsible loess foundation treatment.
Water plays a pivotal role in influencing collapsible loess foundation. In this article, the physical and mechanical parameters of loess and lime soil in Lanzhou are obtained through indoor geotechnical test. The effect of different structures to control lateral seepage in subgrade loess soil is studied through indoor model test. At the same time, the settlement of roadbed is monitored. The experimental results reveal that the permeability coefficient of the lime soil is much less than the coefficient of permeability of loess. After processed by lime-soil compaction pile and lime-soil impervious wall, the moisture content of loess is far less than the value that the lateral seepage control processing is not made. Collapsibility deformation of subgrade is obviously improved. The effect of lime-soil impervious wall is better than the lime-soil compaction pile. The test results can guide the collapsible loess subgrade seepage prevention effectively, and provide a new idea for collapsible loess foundation treatment.
2017, 25(2): 336-343.
For simulating the stress status and existing environment of the rock mass, a set of high pressure triaxial testing machine that can simulate various solution environments is needed to develop. A high pressure hydraulic system is designed in this paper. It can drive four pressure chambers at the same time. Supercharging of the system, joint structure sealing, the separation of the loading installation and liquids, system control methods are all discussed in details. A supercharging pressure cylinder is added to improve the confining pressure. A slant T-shape sealing method and isolation membrane are designed to strengthen the structure join static sealing performance and isolate the solution from pressure chamber. In the end the designed hydraulic system is simulated using the Sim-Hydraulic in MATLAB.The responsible speed of the co-ordinate control and the master-slave control of hydraulic cylinder is analyzed respectively with the adaptive Fuzzy-PID algorithm. The anti-jamming performance of system is also analyzed with the PID control and the adaptive Fuzzy PID control, respectively. Simulating results show that, the system shows better anti-disturbance ability under the adaptive Fuzzy-PID control comparing to the PID control. The hydraulic cylinder shows faster response speed under the adaptive Fuzzy-PID algorithm. This analysis can provide references to the design of triaxial hydraulic loading installation for rock.
For simulating the stress status and existing environment of the rock mass, a set of high pressure triaxial testing machine that can simulate various solution environments is needed to develop. A high pressure hydraulic system is designed in this paper. It can drive four pressure chambers at the same time. Supercharging of the system, joint structure sealing, the separation of the loading installation and liquids, system control methods are all discussed in details. A supercharging pressure cylinder is added to improve the confining pressure. A slant T-shape sealing method and isolation membrane are designed to strengthen the structure join static sealing performance and isolate the solution from pressure chamber. In the end the designed hydraulic system is simulated using the Sim-Hydraulic in MATLAB.The responsible speed of the co-ordinate control and the master-slave control of hydraulic cylinder is analyzed respectively with the adaptive Fuzzy-PID algorithm. The anti-jamming performance of system is also analyzed with the PID control and the adaptive Fuzzy PID control, respectively. Simulating results show that, the system shows better anti-disturbance ability under the adaptive Fuzzy-PID control comparing to the PID control. The hydraulic cylinder shows faster response speed under the adaptive Fuzzy-PID algorithm. This analysis can provide references to the design of triaxial hydraulic loading installation for rock.
2017, 25(2): 344-351.
The pattern and extend of turbulence to surrounding rock, produced by the tunnel constructions are different between shield and mine tunneling methods. The mutual turbulence in tunnels in parallel proximity are to be different between shield and mine tunneling methods. This paper is based on the tunnel construction using both shield and mine tunneling methods in small clear distance in Baifo tunnel section in 1# route in Nanning Rail Transit. The monitoring system is established according to the real construction progress. The mutual turbulence in vertical and horizontal displacements produced by each other is analyzed. When the shield tunnel is constructed backward, the push function of the shield can promote the tunnel constructed with mine tunneling method forward to produce crown rising and clearance contraction. The soften function by the shield to the surrounding rock and the settlement function by the shield construction, can promote the tunnel constructed with mine tunneling method forward to produce crown settlement and clearance dilatation. When the tunnel with mine tunneling method is constructed backward, its side unloading function can promote the tunnel constructed with shield method forward to produce lining rising and clearance dilatation. The research results have revealed the mutual turbulence principle between the two parallel tunnels with shield and mine tunneling methods, which can supply technique support for the construction sequence choice and auxiliary construction measures choice, for similar small clear distance parallel tunnels.
The pattern and extend of turbulence to surrounding rock, produced by the tunnel constructions are different between shield and mine tunneling methods. The mutual turbulence in tunnels in parallel proximity are to be different between shield and mine tunneling methods. This paper is based on the tunnel construction using both shield and mine tunneling methods in small clear distance in Baifo tunnel section in 1# route in Nanning Rail Transit. The monitoring system is established according to the real construction progress. The mutual turbulence in vertical and horizontal displacements produced by each other is analyzed. When the shield tunnel is constructed backward, the push function of the shield can promote the tunnel constructed with mine tunneling method forward to produce crown rising and clearance contraction. The soften function by the shield to the surrounding rock and the settlement function by the shield construction, can promote the tunnel constructed with mine tunneling method forward to produce crown settlement and clearance dilatation. When the tunnel with mine tunneling method is constructed backward, its side unloading function can promote the tunnel constructed with shield method forward to produce lining rising and clearance dilatation. The research results have revealed the mutual turbulence principle between the two parallel tunnels with shield and mine tunneling methods, which can supply technique support for the construction sequence choice and auxiliary construction measures choice, for similar small clear distance parallel tunnels.
2017, 25(2): 352-358.
This paper aims to better understand the shear deformation characteristic of anchorage body-soil interface with the changes of water content and dry density on colluvium soil. It uses an independently developed test method and devise that is based on infinitesimal method. It studies anchor-soil interface friction performance and designs an experiment plan with uniform design method. The result shows that the whole process of anchorage body-soil interface shear stress with shear deformation under different water contents and dry density values. The results' shape conforms to Trilinear Model. An empirical formula is established by means of regression analysis method. It indicates the peak shear strength of anchorage body-soil interface with water content and dry density. Meanwhile, the results show that the peak of anchorage body-soil interface shear strength decreases with the increase of water content. The more the dry density is, the more it decreases. The peak of shear strength decreases with the decrease of dry density. The smaller the water content, the greater the reduction.
This paper aims to better understand the shear deformation characteristic of anchorage body-soil interface with the changes of water content and dry density on colluvium soil. It uses an independently developed test method and devise that is based on infinitesimal method. It studies anchor-soil interface friction performance and designs an experiment plan with uniform design method. The result shows that the whole process of anchorage body-soil interface shear stress with shear deformation under different water contents and dry density values. The results' shape conforms to Trilinear Model. An empirical formula is established by means of regression analysis method. It indicates the peak shear strength of anchorage body-soil interface with water content and dry density. Meanwhile, the results show that the peak of anchorage body-soil interface shear strength decreases with the increase of water content. The more the dry density is, the more it decreases. The peak of shear strength decreases with the decrease of dry density. The smaller the water content, the greater the reduction.
2017, 25(2): 359-366.
In order to study the influence of confining pressure to deformation and failure characteristics and energy evolution characteristics of phyllite, the conventional triaxial compression test is carried out with MTS815 servo-controlled rock mechanical test system. The results show the follows. As the confining pressure increases, the failure mode of phyllite changes from shear failure to mixed tensile-shear failure. The point k is the intersection of the curve of elastic strain energy and the curve of dissipation, before the k point of energy accumulation and after the k point of energy dissipation, respectively. In the early stage of loading, the curve of total energy and axial strain is concave curve, where the energy growth rate is to rise. In the later stage of loading, the curve of total energy and axial strain is convex curve, where the growth rate of energy reduces. At the point of peak strength, the total energy and energy storage limit has a linear relationship with the confining pressure. Confining pressure can hinder the crack propagation and energy release.
In order to study the influence of confining pressure to deformation and failure characteristics and energy evolution characteristics of phyllite, the conventional triaxial compression test is carried out with MTS815 servo-controlled rock mechanical test system. The results show the follows. As the confining pressure increases, the failure mode of phyllite changes from shear failure to mixed tensile-shear failure. The point k is the intersection of the curve of elastic strain energy and the curve of dissipation, before the k point of energy accumulation and after the k point of energy dissipation, respectively. In the early stage of loading, the curve of total energy and axial strain is concave curve, where the energy growth rate is to rise. In the later stage of loading, the curve of total energy and axial strain is convex curve, where the growth rate of energy reduces. At the point of peak strength, the total energy and energy storage limit has a linear relationship with the confining pressure. Confining pressure can hinder the crack propagation and energy release.
2017, 25(2): 367-375.
This paper attempts to reveal the variation of physical and mechanical properties of the rock mass in the reservoir water level under the condition of periodic fluctuation of the water level in the reservoir. It tries to master the process and the difference of the deterioration of the rock mass. It chooses the Jurassic slope with deformation and destruction seriously in water level-fluctuating zone. On the basis of macroscopic investigation, single hole and cross hole sonic wave testing method is used for in-situ test. Meanwhile, the samples are collected and tested by dry-wet circulation, mechanical and disintegration tests. In-situ single-hole acoustic wave test KV value is 0.2~0.51 and its cross-hole value is 0.46~0.91. It shows that the integrity of rock mass is poor in transverse and better in the longitudinal. The integrity of the rock mass decreases with the decrease of elevation. Mechanical test results show that the specimen strength decreases 30%~45% on average after 20 times dry-wet circulation. The coefficient of friction and cohesion parameters is gradually decreased. The disintegration resistance test shows that under the condition of dry wet cycle, the disintegration resistance of the rock decreases gradually, after 5 cycles of dry-wet cycles, the index of disintegration resistance decreases by 3.1%~20.2%.The experimental results show that the rock mass is affected by reservoir water strongly in water level-fluctuating zone. The physical and mechanical properties of rock mass are decreased under the condition of dry-wet cycle for a long time. Different lithology deterioration degree is different. The trend of rock mass develops to break and disintegration, which has progressive and cumulative features.
This paper attempts to reveal the variation of physical and mechanical properties of the rock mass in the reservoir water level under the condition of periodic fluctuation of the water level in the reservoir. It tries to master the process and the difference of the deterioration of the rock mass. It chooses the Jurassic slope with deformation and destruction seriously in water level-fluctuating zone. On the basis of macroscopic investigation, single hole and cross hole sonic wave testing method is used for in-situ test. Meanwhile, the samples are collected and tested by dry-wet circulation, mechanical and disintegration tests. In-situ single-hole acoustic wave test KV value is 0.2~0.51 and its cross-hole value is 0.46~0.91. It shows that the integrity of rock mass is poor in transverse and better in the longitudinal. The integrity of the rock mass decreases with the decrease of elevation. Mechanical test results show that the specimen strength decreases 30%~45% on average after 20 times dry-wet circulation. The coefficient of friction and cohesion parameters is gradually decreased. The disintegration resistance test shows that under the condition of dry wet cycle, the disintegration resistance of the rock decreases gradually, after 5 cycles of dry-wet cycles, the index of disintegration resistance decreases by 3.1%~20.2%.The experimental results show that the rock mass is affected by reservoir water strongly in water level-fluctuating zone. The physical and mechanical properties of rock mass are decreased under the condition of dry-wet cycle for a long time. Different lithology deterioration degree is different. The trend of rock mass develops to break and disintegration, which has progressive and cumulative features.
2017, 25(2): 376-383.
It is very important to study the evolution law of fracture development in loess under humidification-dehumidification, because there are various cracks in the loess. Humidification-dehumidification lead to the development of internal cracks in undisturbed loess. The loess in Yan'an area is used as the research object. The soil microstructure change map of humidification-dehumidification and the soil sample CT number ME and SD values of soil samples with humidifier-dehumidification effect curve are obtained by CT scanning technology. The results show that: as soil moisture increases, the internal damage rate of soil is increased slowly, when the water content over the plastic limit of the soil sample. Soil internal damage rate increases slowly, when the moisture content exceeds a certain limit. The rate will fall. CT numbers mean and variance with moisture content changes are highly anti-"s" curve. With the dry-wet recycle number increases, the microcracks in soil samples, develop gradually and show elongation widened irregular bifurcation. After 4 dry-wet recycles, the ground fissures have been basically formed. The soil sample fracture and the CT number have little change. The more wet-dry recycle, the more damage degree of internal soil samples and development of internal joints and fissures in soil sample.
It is very important to study the evolution law of fracture development in loess under humidification-dehumidification, because there are various cracks in the loess. Humidification-dehumidification lead to the development of internal cracks in undisturbed loess. The loess in Yan'an area is used as the research object. The soil microstructure change map of humidification-dehumidification and the soil sample CT number ME and SD values of soil samples with humidifier-dehumidification effect curve are obtained by CT scanning technology. The results show that: as soil moisture increases, the internal damage rate of soil is increased slowly, when the water content over the plastic limit of the soil sample. Soil internal damage rate increases slowly, when the moisture content exceeds a certain limit. The rate will fall. CT numbers mean and variance with moisture content changes are highly anti-"s" curve. With the dry-wet recycle number increases, the microcracks in soil samples, develop gradually and show elongation widened irregular bifurcation. After 4 dry-wet recycles, the ground fissures have been basically formed. The soil sample fracture and the CT number have little change. The more wet-dry recycle, the more damage degree of internal soil samples and development of internal joints and fissures in soil sample.
2017, 25(2): 384-392.
This paper evaluates surrounding rock stability and tunnel spacing of rationality of the long and deep tunnel.3D geomechanical model way is used to study the surrounding rock total stability and the effects mutually from adjacent tunnel excavation under high geostress and high groundwater pressure.3D geomechanical model results are compared with 3D Elastoplastic FEM calculated results. Research results show that the results of 3D geomechanical model experiment and 3D Elastoplastic FEM consideration are consistent. The displacement fields, stress fields and yield area range are consistent. Tunnel project with Ⅲ class of surrounding rock mass is safe under high geostress and high groundwater pressure. Limit overload safety factor is general more than 1.3, experiment with overload under high geostress surrounding rock. The influence area of displacement and stress of excavation tunnel is generally less than one times the tunnel hole diameter range. The tunnel spacing is apposite.
This paper evaluates surrounding rock stability and tunnel spacing of rationality of the long and deep tunnel.3D geomechanical model way is used to study the surrounding rock total stability and the effects mutually from adjacent tunnel excavation under high geostress and high groundwater pressure.3D geomechanical model results are compared with 3D Elastoplastic FEM calculated results. Research results show that the results of 3D geomechanical model experiment and 3D Elastoplastic FEM consideration are consistent. The displacement fields, stress fields and yield area range are consistent. Tunnel project with Ⅲ class of surrounding rock mass is safe under high geostress and high groundwater pressure. Limit overload safety factor is general more than 1.3, experiment with overload under high geostress surrounding rock. The influence area of displacement and stress of excavation tunnel is generally less than one times the tunnel hole diameter range. The tunnel spacing is apposite.
2017, 25(2): 393-401.
3D Geological modeling technology can more intuitively represents the 3D structures and spatial distribution of rock formations of subsurface, when it is compared with traditional 2D geological mapping technology. It has important applications in planning, design, construction and risk assessment of the engineering projects. Modeling objects often involves complex geological bodies in engineering fields. In order to improve the automatic level of 3D geological modeling, this paper proposes an automatic method of modeling complex geological bodies based on ArcGIS Model Builder. First, the borehole data and geological section maps are used as data source. The Python object-oriented programming language and ArcPy package are combined for automatic preprocessing of the drilling data. Secondly, the function of automatic vectorization of ArcScan and the human computer interaction (HCI) of SkechUp are combined for extracting the 2D and 3D fault lines and then stored in GIS spatial database. Thirdly, the Model Builder of ArcGIS, a visual modeling tool, is used for automatically creating the 3D solid models of strata and the 3D surface models of faults using the data processing, file conversion and 3D analysis tools of the ArcToolbox. Fourthly, the cutting, cross-section and excavation polygons are vectorized respectively as the inputs of the 3D analyst tool of Extrude between extended using ArcPy. The 3D visualization tool of ArcScene is used for realizing multiple types of visualization. Finally, the drilling data acquired from the 3D geological survey in Nanjing Xianlin area are used for practical modeling test. The modeling results show that the method has accurate, rapid and automatic advantages, which can provide reliable technical solutions for large-scale and mass geological modeling.
3D Geological modeling technology can more intuitively represents the 3D structures and spatial distribution of rock formations of subsurface, when it is compared with traditional 2D geological mapping technology. It has important applications in planning, design, construction and risk assessment of the engineering projects. Modeling objects often involves complex geological bodies in engineering fields. In order to improve the automatic level of 3D geological modeling, this paper proposes an automatic method of modeling complex geological bodies based on ArcGIS Model Builder. First, the borehole data and geological section maps are used as data source. The Python object-oriented programming language and ArcPy package are combined for automatic preprocessing of the drilling data. Secondly, the function of automatic vectorization of ArcScan and the human computer interaction (HCI) of SkechUp are combined for extracting the 2D and 3D fault lines and then stored in GIS spatial database. Thirdly, the Model Builder of ArcGIS, a visual modeling tool, is used for automatically creating the 3D solid models of strata and the 3D surface models of faults using the data processing, file conversion and 3D analysis tools of the ArcToolbox. Fourthly, the cutting, cross-section and excavation polygons are vectorized respectively as the inputs of the 3D analyst tool of Extrude between extended using ArcPy. The 3D visualization tool of ArcScene is used for realizing multiple types of visualization. Finally, the drilling data acquired from the 3D geological survey in Nanjing Xianlin area are used for practical modeling test. The modeling results show that the method has accurate, rapid and automatic advantages, which can provide reliable technical solutions for large-scale and mass geological modeling.
2017, 25(2): 402-409.
The Brazilian tests on Cracked Straight Through Brazilian Disc (CSTBD) specimens are simulated using Particle Flow Code (PFC). Then, the effects of inclination angle and length of the pre-existing crack on the crack evolution behavior are analyzed. The results indicate that depending on the crack initiation positions, two types of main crack exist, including mode Ⅰ main crack and mode Ⅱ main crack. Mode Ⅰ main crack is initiated at the tip of the pre-existing crack. And mode Ⅱ main crack is initiated at a distance from the tip of the pre-existing crack. There also exist two types of secondary crack, including mode Ⅰ secondary crack and mode Ⅱ secondary crack. Mode Ⅰ secondary crack is initiated near the load point. And mode Ⅱ secondary crack is initiated at a distance from the load point. When the crack length keeps constant and inclination angle increases, main crack would change from mode Ⅰ to mode Ⅱ and secondary crack would change from mode Ⅰ to mixed-mode (Ⅰ+Ⅱ), and finally transform into mode Ⅰ. When the inclination angle keep constant and crack length increases, main crack keep steady and secondary crack would change from mode Ⅰ to mixed-mode (Ⅰ+Ⅱ). After the radial stress exceeds the peak stress of the specimen, a large number of micro cracks would develop and propagate, which lead to the broke of the Brazil disc. The failure process of Brazil disc is mainly resulted from the ruptures of inter-particle bonding caused by tensile stress concentration and internal strain energy release.
The Brazilian tests on Cracked Straight Through Brazilian Disc (CSTBD) specimens are simulated using Particle Flow Code (PFC). Then, the effects of inclination angle and length of the pre-existing crack on the crack evolution behavior are analyzed. The results indicate that depending on the crack initiation positions, two types of main crack exist, including mode Ⅰ main crack and mode Ⅱ main crack. Mode Ⅰ main crack is initiated at the tip of the pre-existing crack. And mode Ⅱ main crack is initiated at a distance from the tip of the pre-existing crack. There also exist two types of secondary crack, including mode Ⅰ secondary crack and mode Ⅱ secondary crack. Mode Ⅰ secondary crack is initiated near the load point. And mode Ⅱ secondary crack is initiated at a distance from the load point. When the crack length keeps constant and inclination angle increases, main crack would change from mode Ⅰ to mode Ⅱ and secondary crack would change from mode Ⅰ to mixed-mode (Ⅰ+Ⅱ), and finally transform into mode Ⅰ. When the inclination angle keep constant and crack length increases, main crack keep steady and secondary crack would change from mode Ⅰ to mixed-mode (Ⅰ+Ⅱ). After the radial stress exceeds the peak stress of the specimen, a large number of micro cracks would develop and propagate, which lead to the broke of the Brazil disc. The failure process of Brazil disc is mainly resulted from the ruptures of inter-particle bonding caused by tensile stress concentration and internal strain energy release.
2017, 25(2): 410-415.
This paper aims to examine the effect of cyclic variation of temperature on rock mechanical property. Altered rock are selected and rock mechanics test is carried out to examine the effect of different temperature circulating frequencies. Based on the analysis of experimental data, the function is established to describe the variation pattern of mechanical properties of altered rock by cyclic temperature. It is shown that the mechanical properties of the altered rocks are obviously weakened by temperature cycle effects. With the increase of temperature cycle times, the peak strength, elastic modulus and tensile strength are decreased and the Poisson's ratio is almost constant. As the degree of alteration and fragmentation increases, the degree of damage increases. For the cyclic temperature to the mechanical properties of rock the phenomenon is more obvious. After 20 times, the damage rates of tensile strength, peaky peak intensity and elastic modulus can reach 42.38%, 34.69% and 29.57% respectively. The variation of the mechanical parameters of the altered rock and the cumulative damage rate with the change of the temperature cycle times are all subject to the exponential distribution.
This paper aims to examine the effect of cyclic variation of temperature on rock mechanical property. Altered rock are selected and rock mechanics test is carried out to examine the effect of different temperature circulating frequencies. Based on the analysis of experimental data, the function is established to describe the variation pattern of mechanical properties of altered rock by cyclic temperature. It is shown that the mechanical properties of the altered rocks are obviously weakened by temperature cycle effects. With the increase of temperature cycle times, the peak strength, elastic modulus and tensile strength are decreased and the Poisson's ratio is almost constant. As the degree of alteration and fragmentation increases, the degree of damage increases. For the cyclic temperature to the mechanical properties of rock the phenomenon is more obvious. After 20 times, the damage rates of tensile strength, peaky peak intensity and elastic modulus can reach 42.38%, 34.69% and 29.57% respectively. The variation of the mechanical parameters of the altered rock and the cumulative damage rate with the change of the temperature cycle times are all subject to the exponential distribution.
2017, 25(2): 416-423.
Current research of the impact of landslide creep on bridge across the landslide is far from consummate. Measured data is deficient as well. On the basis of long-term monitoring of Zhengjiawan landslide and the bridge across it, the potential sliding surfaces of landslide are inferred according to monitoring data of deep displacement. The influence of meteorological factors on the monitoring data is analyzed. Moreover, the correlation between the creep of landslide and bridge deformation is studied. Study results show as follows. (1) Depth of Zhenjiawan landslide is 3~19m, and monthly displacement is 0.64~5.16mm, and the cumulative displacement is 20~62mm, which proves that the landslide is creeping intermittently.(2) The deformation of Zhengjiawan landslide and bridge is dominated by rainfall. During the monitoring period the maximum monthly rainfall is 390.2mm. At the same moment the largest deformation of landslide and bridge is 2mm·month-1 and 7mm·month-1.(3) The deformation of bridge and landslide is synchronous. The monthly displacement difference is 0.24~2.13mm. The cumulative displacement difference is 6.3mm. Data and results of this paper has important significance to the management of Zhengjiawan landslide and the analysis of similar bridges across landslide.
Current research of the impact of landslide creep on bridge across the landslide is far from consummate. Measured data is deficient as well. On the basis of long-term monitoring of Zhengjiawan landslide and the bridge across it, the potential sliding surfaces of landslide are inferred according to monitoring data of deep displacement. The influence of meteorological factors on the monitoring data is analyzed. Moreover, the correlation between the creep of landslide and bridge deformation is studied. Study results show as follows. (1) Depth of Zhenjiawan landslide is 3~19m, and monthly displacement is 0.64~5.16mm, and the cumulative displacement is 20~62mm, which proves that the landslide is creeping intermittently.(2) The deformation of Zhengjiawan landslide and bridge is dominated by rainfall. During the monitoring period the maximum monthly rainfall is 390.2mm. At the same moment the largest deformation of landslide and bridge is 2mm·month-1 and 7mm·month-1.(3) The deformation of bridge and landslide is synchronous. The monthly displacement difference is 0.24~2.13mm. The cumulative displacement difference is 6.3mm. Data and results of this paper has important significance to the management of Zhengjiawan landslide and the analysis of similar bridges across landslide.
2017, 25(2): 436-446.
Chun'an county is located in southeast China, where is a typical region with extensive occurrence of rainfall-triggered landslides. Based on the results of detailed field investigation of geohazard in Chun'an county, this study applies GIS and Certainty Factor (CF) method to analyze the susceptibility of 9 landslide controlling factors. They include elevation, slope gradient, aspect, curvature, lithology, distance to fault, distance to roads, land use and vegetation. The results from CF analysis show that (1) stratigraphy of Cambrian, Sinian, Carboniferous and Cretaceous, and lithology of the intrusive rock group, red sandstone rock group, carbonatite mixed clasolite rock group, and carbonatite rock group are more susceptible to landslide. The affection of fault to landslide susceptibility in this study area decreases with the increasing of the distance to fault.(2) the areas relatively more susceptible to landslide occurrence include the areas with slope gradient between 10°~35°, aspects of south-facing in south and southeast direction, elevation between 100 and 200m, concave slope and straight slope, vegetation with non-forest, economic forest, tea and bamboo forest. The quantity of occurred landslides reaches to its peak in areas with slope gradient in a range from 30°and 35°.(3) the land use types with extensive anthropogenic activities such as residential land, cultivated land, transportation land and garden are prone to landslides. The controlling factor of distance to roads has less influence on landslide susceptibility and there is no significant correlation between them. This study will facilitate determination of categories with associated numerical intervals of each controlling factor, which is the fundamental in rainfall-triggered landslide susceptibility assessment and spatial prediction.
Chun'an county is located in southeast China, where is a typical region with extensive occurrence of rainfall-triggered landslides. Based on the results of detailed field investigation of geohazard in Chun'an county, this study applies GIS and Certainty Factor (CF) method to analyze the susceptibility of 9 landslide controlling factors. They include elevation, slope gradient, aspect, curvature, lithology, distance to fault, distance to roads, land use and vegetation. The results from CF analysis show that (1) stratigraphy of Cambrian, Sinian, Carboniferous and Cretaceous, and lithology of the intrusive rock group, red sandstone rock group, carbonatite mixed clasolite rock group, and carbonatite rock group are more susceptible to landslide. The affection of fault to landslide susceptibility in this study area decreases with the increasing of the distance to fault.(2) the areas relatively more susceptible to landslide occurrence include the areas with slope gradient between 10°~35°, aspects of south-facing in south and southeast direction, elevation between 100 and 200m, concave slope and straight slope, vegetation with non-forest, economic forest, tea and bamboo forest. The quantity of occurred landslides reaches to its peak in areas with slope gradient in a range from 30°and 35°.(3) the land use types with extensive anthropogenic activities such as residential land, cultivated land, transportation land and garden are prone to landslides. The controlling factor of distance to roads has less influence on landslide susceptibility and there is no significant correlation between them. This study will facilitate determination of categories with associated numerical intervals of each controlling factor, which is the fundamental in rainfall-triggered landslide susceptibility assessment and spatial prediction.
2017, 25(2): 447-454.
The large and professional unmanned aerial vehicle based remote sensing (UAVRS) system has been widely used for the emergency survey of the wide range of geo-hazards. In this paper, the more simple and flexible micro-UAVRS method for the emergency survey of individual geo-hazard is put forward, based on a number of successful practices of emergency survey for geo-hazards in the Three Gorges Reservoir in recent years. The method includes: assembling a multi-rotor micro-UAVRS system that is more applicable for the emergency survey of the individual geo-hazard; developing the specific implementation process; and elaborating some crucial technologies and methods such as the arrangement and measurement of ground control points, the design of flight plan according to the features of geo-hazard, the control of the micro-UAVRS' flight and photos acquisition, and the image processing, etc. Practice shows that, using the micro-UAVRS method for the emergency survey of individual geo-hazard is useful, and capable of achieving the goal of fast & efficient, because the method can not only greatly reduce the work time, strength and risks, but also provide the high-precision remote sensing results and data.
The large and professional unmanned aerial vehicle based remote sensing (UAVRS) system has been widely used for the emergency survey of the wide range of geo-hazards. In this paper, the more simple and flexible micro-UAVRS method for the emergency survey of individual geo-hazard is put forward, based on a number of successful practices of emergency survey for geo-hazards in the Three Gorges Reservoir in recent years. The method includes: assembling a multi-rotor micro-UAVRS system that is more applicable for the emergency survey of the individual geo-hazard; developing the specific implementation process; and elaborating some crucial technologies and methods such as the arrangement and measurement of ground control points, the design of flight plan according to the features of geo-hazard, the control of the micro-UAVRS' flight and photos acquisition, and the image processing, etc. Practice shows that, using the micro-UAVRS method for the emergency survey of individual geo-hazard is useful, and capable of achieving the goal of fast & efficient, because the method can not only greatly reduce the work time, strength and risks, but also provide the high-precision remote sensing results and data.
2017, 25(2): 455-462.
Simulations of landslide run-out can avoid the limit of experiment and instrumentation. It can observe the movement processes in detail. It is essential to the quantitative hazard assessment for landslide. for the simulation of landslide movement, the primary work is to establish a landslide model. Although the Particle Flow Code (PFC) is one of the most widely used program for landslide modeling, it is weak in the pre-processing of building the landslide model. This limits its application to landslide modeling. As for this, this paper illustrates the applicability, advantages and disadvantages of the Ball-Ball and Ball-Wall methods for model building. The way to determine the boundary of sliding mass and sliding bed is presented. It is based on the digital elevation map and the Brick filling method. It takes the earthquake-induced Red Rock Landslide as an example. Four steps are presented to build 2D & 3D landslide model with PFC.The four steps are obtaining topographic data, determining the boundary of both sliding mass and sliding bed, building the geometry of both sliding mass and sliding bed, filling the geometry with particles. By this way, the 2D and 3D landslide model can be easily and quickly built with PFC.The presented method will be helpful to the simulation of landslide movement with PFC.
Simulations of landslide run-out can avoid the limit of experiment and instrumentation. It can observe the movement processes in detail. It is essential to the quantitative hazard assessment for landslide. for the simulation of landslide movement, the primary work is to establish a landslide model. Although the Particle Flow Code (PFC) is one of the most widely used program for landslide modeling, it is weak in the pre-processing of building the landslide model. This limits its application to landslide modeling. As for this, this paper illustrates the applicability, advantages and disadvantages of the Ball-Ball and Ball-Wall methods for model building. The way to determine the boundary of sliding mass and sliding bed is presented. It is based on the digital elevation map and the Brick filling method. It takes the earthquake-induced Red Rock Landslide as an example. Four steps are presented to build 2D & 3D landslide model with PFC.The four steps are obtaining topographic data, determining the boundary of both sliding mass and sliding bed, building the geometry of both sliding mass and sliding bed, filling the geometry with particles. By this way, the 2D and 3D landslide model can be easily and quickly built with PFC.The presented method will be helpful to the simulation of landslide movement with PFC.
2017, 25(2): 463-471.
Xieliupo landslide in Zhouqu is a typical landslide in fracture zone. The fault not only controls the landslide boundary, but also affects its deformation. In this paper, the deformation and stress of landslide is discussed using finite element method with Drucker-Prager soil rheological constitutive model. The results are as follows. (1) The plastic deformation of soil is strongly affected by the faults. It is worse than that of footwall fault in the boundary of landslide. (2) There is alternant distribution of accumulation zone and cracking zone in landslide mass. (3) It is in the state of creeping deformation and the max deformation occurs in the center of the landslide with 0.3m per year. (4) The surcharge loading can significantly relieve pavement deformation of Highway No.S313.
Xieliupo landslide in Zhouqu is a typical landslide in fracture zone. The fault not only controls the landslide boundary, but also affects its deformation. In this paper, the deformation and stress of landslide is discussed using finite element method with Drucker-Prager soil rheological constitutive model. The results are as follows. (1) The plastic deformation of soil is strongly affected by the faults. It is worse than that of footwall fault in the boundary of landslide. (2) There is alternant distribution of accumulation zone and cracking zone in landslide mass. (3) It is in the state of creeping deformation and the max deformation occurs in the center of the landslide with 0.3m per year. (4) The surcharge loading can significantly relieve pavement deformation of Highway No.S313.
2017, 25(2): 472-479.
Jiawu gold mine is located in Qinghai Nanshan micro orogenic belt in the east margin of Qaidam Basin, Qinghai-Tibetan Plateau area. The objectives of this work is to ensure the progress of the mineral exploration and mining and to prevent the occurrence effectively of the sudden geological disaster, such as debris flow within the area. A full awareness of the background of the sudden debris flows is established by conducting a detailed investigation of the debris flow, especially the systematically investigation of the Maridang gully river basin, where is the key work area of the mining area. Based on this, we study the starting mechanism of Maridang gully debris flow systematically according to the research achievement of Fei et al.(2004). It was about the starting conditions of debris flow containing fine particles and the meteorological observation data in Tongde county, Qinghai province. The results show that the critical rainfall value of debris flow in Jiawu mining area, Maridang gully, has favorable conditions of the sudden debris flow. The conditions include terrain, source and water power. The debris flows in this area belong to the typical diluted debris flows, or water stone debris flows. They have the following characters: fluid velocity UW≥5.35m·s-1 and unit weight γc≤1.511t·m-3.
Jiawu gold mine is located in Qinghai Nanshan micro orogenic belt in the east margin of Qaidam Basin, Qinghai-Tibetan Plateau area. The objectives of this work is to ensure the progress of the mineral exploration and mining and to prevent the occurrence effectively of the sudden geological disaster, such as debris flow within the area. A full awareness of the background of the sudden debris flows is established by conducting a detailed investigation of the debris flow, especially the systematically investigation of the Maridang gully river basin, where is the key work area of the mining area. Based on this, we study the starting mechanism of Maridang gully debris flow systematically according to the research achievement of Fei et al.(2004). It was about the starting conditions of debris flow containing fine particles and the meteorological observation data in Tongde county, Qinghai province. The results show that the critical rainfall value of debris flow in Jiawu mining area, Maridang gully, has favorable conditions of the sudden debris flow. The conditions include terrain, source and water power. The debris flows in this area belong to the typical diluted debris flows, or water stone debris flows. They have the following characters: fluid velocity UW≥5.35m·s-1 and unit weight γc≤1.511t·m-3.
2017, 25(2): 488-495.
During the operation of the Three Gorges Project, the reservoir water level changes according to the actual condition of water storage and hydrologic condition. Because of the correlation between the underground water level of landslides and the reservoir water level, water level cyclical fluctuation may have effects on the landslides in many ways. The effects cause the changes of the stability of landslide in the reservoir area. Permeability is the internal property of landslide. The permeability coefficient can be used to characterize the hydraulic conductivity of the soil. It is also the main factor influencing the characteristics of seepage field of the landslides on the reservoir bank. The stability of the landslides responds differently to the changes of the reservoir water level, due to different permeability of the landslides. According to the statistics of the reservoir water level of the Wanzhou, we take the Xiaping landslide in Wanzhou district of the Three Gorges Reservoir area as a model. We study the variation law of the stability of landslides with different permeability coefficients by analyzing the characteristics of seepage field under 4 different orders of magnitude of permeability coefficient. The results show that the variation of the stability of this type of landslides shows highly positive correlation with the variation of the reservoir water level. The worst stability of the landslide appears when the water level is dropped to the lowest level. And the faster water level drops, the worse the stability of landslide becomes. The regularities of the coefficients of landslide stability changed with the time are almost the same under different permeable conditions. The variation ratio of the coefficient fluctuates within a certain range between-2% to 2%.The maximum and minimum of the landslide stability go after the permeability. As the permeability of the landslide decreases, the response of the groundwater to the reservoir water level fluctuation becomes more and more weak. The minimum of the landslide stability shows an approximately exponential relationship with the logarithm of permeability coefficient. The maximum of the landslide stability shows an approximately logarithmic relationship with the logarithm of permeability coefficient.
During the operation of the Three Gorges Project, the reservoir water level changes according to the actual condition of water storage and hydrologic condition. Because of the correlation between the underground water level of landslides and the reservoir water level, water level cyclical fluctuation may have effects on the landslides in many ways. The effects cause the changes of the stability of landslide in the reservoir area. Permeability is the internal property of landslide. The permeability coefficient can be used to characterize the hydraulic conductivity of the soil. It is also the main factor influencing the characteristics of seepage field of the landslides on the reservoir bank. The stability of the landslides responds differently to the changes of the reservoir water level, due to different permeability of the landslides. According to the statistics of the reservoir water level of the Wanzhou, we take the Xiaping landslide in Wanzhou district of the Three Gorges Reservoir area as a model. We study the variation law of the stability of landslides with different permeability coefficients by analyzing the characteristics of seepage field under 4 different orders of magnitude of permeability coefficient. The results show that the variation of the stability of this type of landslides shows highly positive correlation with the variation of the reservoir water level. The worst stability of the landslide appears when the water level is dropped to the lowest level. And the faster water level drops, the worse the stability of landslide becomes. The regularities of the coefficients of landslide stability changed with the time are almost the same under different permeable conditions. The variation ratio of the coefficient fluctuates within a certain range between-2% to 2%.The maximum and minimum of the landslide stability go after the permeability. As the permeability of the landslide decreases, the response of the groundwater to the reservoir water level fluctuation becomes more and more weak. The minimum of the landslide stability shows an approximately exponential relationship with the logarithm of permeability coefficient. The maximum of the landslide stability shows an approximately logarithmic relationship with the logarithm of permeability coefficient.
2017, 25(2): 496-503.
Through the typical case investigation, this paper proposes evolutionary theory for gently inclined bedding rock landslide at east Sichuan. It further proposed the identification for different stages of evolution characteristics. The main findings are as follows. The first is the initial short-distance start-up phase. Deep fissures are mainly showed after the ramp edge. The second is the medium-term troughs expansion phase. Trench and groove (or depression pull ramp of catchment aggregation and occurrence of drama slippery topographical features) are mainly showed after ramp edge. They include chair-like terrain, three-channel surround or homologous Shuang'gou terrain, as well as terrain trailing edge of depression. Thirdly, large to extra-large rock bedded slope landslide is mostly the result of twice or even three times of starting to sliding in slope. Identification of the ancient (old) delineation of a large landslide is one of the important ways large rock bedded landslide. Fourthly, in the detailed investigation of the geological survey, the survey on slope micro-topography and tensile failure area is focused specially. The investigation is focused on the early short-range and medium-term pull-start groove troughs expansion phase of the insidious slope.
Through the typical case investigation, this paper proposes evolutionary theory for gently inclined bedding rock landslide at east Sichuan. It further proposed the identification for different stages of evolution characteristics. The main findings are as follows. The first is the initial short-distance start-up phase. Deep fissures are mainly showed after the ramp edge. The second is the medium-term troughs expansion phase. Trench and groove (or depression pull ramp of catchment aggregation and occurrence of drama slippery topographical features) are mainly showed after ramp edge. They include chair-like terrain, three-channel surround or homologous Shuang'gou terrain, as well as terrain trailing edge of depression. Thirdly, large to extra-large rock bedded slope landslide is mostly the result of twice or even three times of starting to sliding in slope. Identification of the ancient (old) delineation of a large landslide is one of the important ways large rock bedded landslide. Fourthly, in the detailed investigation of the geological survey, the survey on slope micro-topography and tensile failure area is focused specially. The investigation is focused on the early short-range and medium-term pull-start groove troughs expansion phase of the insidious slope.
2017, 25(2): 504-510.
The in-situ stress near the shallow faults is an important factor affecting underground chamber engineering and or oil exploration and development. Due to the tectonic movements, the shallow fault rocks are in weak cemented state. The conventional methods for measuring in-situ stress exist the deficiencies such as larger error, higher cost, longer cycle and so on. Based on the Mohr-Coulomb strength theory, this paper systematically analyzes the relationship of the in-situ stress near faults, the fault friction coefficient calculation and fault frictional strength. Finally, the in-situ stress model is applied to calculate the stress of Chengzhuang region. The results coincide with the measured results. The results have important implications for stress calculation, and efficient product of oil and gas.
The in-situ stress near the shallow faults is an important factor affecting underground chamber engineering and or oil exploration and development. Due to the tectonic movements, the shallow fault rocks are in weak cemented state. The conventional methods for measuring in-situ stress exist the deficiencies such as larger error, higher cost, longer cycle and so on. Based on the Mohr-Coulomb strength theory, this paper systematically analyzes the relationship of the in-situ stress near faults, the fault friction coefficient calculation and fault frictional strength. Finally, the in-situ stress model is applied to calculate the stress of Chengzhuang region. The results coincide with the measured results. The results have important implications for stress calculation, and efficient product of oil and gas.
2017, 25(2): 511-519.
Because of the complexity and diversity of geohazards, as well as the surroundings interference, their automatic recognitions are in a situation of great difficulty and can't meet the application requirements. Finding an algorithm to extract the common characteristics of a kind of geohazard and to distinguish them from the surroundings is effective for automatic recognition of geohazards. Landslide dams of a certain volume can bring many micro-topographic features by chain processes, such as knickpoints, which is regarded as a key for their remote sensing interpretation and field investigation. From the point of fluvial geomorphology evolution, taking the knickpoints as a common feature of landslide dams, we present a automatic recognition method of landslide dams. It is based on stream length-gradient index, and can provide the computer module by GIS project designing and coding. Using DEM, remote sensing images and geological maps, we apply the method in the upper region of Kangbumaqu, in Yadong Country, Tibet, China, and obtain the following conclusions. (1) For 1:50000 DEM, the reasonable computing interval is 300m, which can reduce data error and highlight terrain differences simultaneously. (2) The three factors with the greatest transformation to fluvial geomorphology in the study area are, in order, landslide dams, lithological changes and tectonic movement. (3) The accuracy of automatic recognition of landslide dams in the study area is 85.71%, indicating the proposed method is feasible for automatic recognition of landslide dams in high mountainous areas.
Because of the complexity and diversity of geohazards, as well as the surroundings interference, their automatic recognitions are in a situation of great difficulty and can't meet the application requirements. Finding an algorithm to extract the common characteristics of a kind of geohazard and to distinguish them from the surroundings is effective for automatic recognition of geohazards. Landslide dams of a certain volume can bring many micro-topographic features by chain processes, such as knickpoints, which is regarded as a key for their remote sensing interpretation and field investigation. From the point of fluvial geomorphology evolution, taking the knickpoints as a common feature of landslide dams, we present a automatic recognition method of landslide dams. It is based on stream length-gradient index, and can provide the computer module by GIS project designing and coding. Using DEM, remote sensing images and geological maps, we apply the method in the upper region of Kangbumaqu, in Yadong Country, Tibet, China, and obtain the following conclusions. (1) For 1:50000 DEM, the reasonable computing interval is 300m, which can reduce data error and highlight terrain differences simultaneously. (2) The three factors with the greatest transformation to fluvial geomorphology in the study area are, in order, landslide dams, lithological changes and tectonic movement. (3) The accuracy of automatic recognition of landslide dams in the study area is 85.71%, indicating the proposed method is feasible for automatic recognition of landslide dams in high mountainous areas.
2017, 25(2): 520-530.
China is a country with many mountains. The risk assessment of rockfall has gained more attention due to the increase of rockfall hazard in mountainous areas. Rockfall risk analysis is inherently complex and difficult. Such difficulties are due to many factors. They include high uncertainties of rockfall occurrence and transport, lack of historical data, strongly site-specific nature of rockfall, difficulty in quantifying and modelling spatial rockfall distribution, quantifying the heterogeneity of vulnerability of different elements at risk and variability in temporal vulnerability, These factors lead many limitations in quantitative risk assessment. Rock falls in Luojiaqinggangling, Sichuan Province are a scarce example to study risk assessment quantitatively due to the complete field data and rich historical data. Based on the engineering geological investigation, topographical survey and statistic analysis, this paper confirms the provenance, accumulation area, maximum transport distance, annual probability of occurrence and four potentially unstable blocks A-D. Rockfall risk for exposed people in Luojiaqinggangling is estimated by the product of three conditional probabilities (annual probability of occurrence, reach probability and temporal-spatial probability) and vulnerability. Based on the rich statistical data of historical rockfall, the annual probability of occurrence is derived from a magnitude-cumulative frequency (MCF) distribution of rockfall events. Considering the size statistical characteristics of the historical rockfall and the position uncertainties of unstable blocks in provenance, this paper conducts the inversion analysis of slope restitution and friction coefficients. It uses the two-dimensional simulation software Rockfall. On these basis, the arrival probabilities of unstable blocks A-D were obtained after numerous random simulation and statistical analysis. Pedestrians and residents that are confirmed as the affected body based on field investigation, temporal-spatial probability depends on the mobility of the exposed elements. It is calculated using empirical equation according to the movement feature of affected body. The vulnerability was determined combining the kinetic energy of rockfall and the location of affected body. According to the product of occurrence probability, arrival probability, temporal distribution probability and vulnerability, the quantitative risk assessment of this rockfall is achieved. The results show that the risk values of block A and D are in a unacceptable risk range, and the risk values of blocks B and C are in a warning range. Those unstable blocks could threaten the life safety of the residents, therefore, it is essential to take appropriate measures for the disaster prevention and mitigation.
China is a country with many mountains. The risk assessment of rockfall has gained more attention due to the increase of rockfall hazard in mountainous areas. Rockfall risk analysis is inherently complex and difficult. Such difficulties are due to many factors. They include high uncertainties of rockfall occurrence and transport, lack of historical data, strongly site-specific nature of rockfall, difficulty in quantifying and modelling spatial rockfall distribution, quantifying the heterogeneity of vulnerability of different elements at risk and variability in temporal vulnerability, These factors lead many limitations in quantitative risk assessment. Rock falls in Luojiaqinggangling, Sichuan Province are a scarce example to study risk assessment quantitatively due to the complete field data and rich historical data. Based on the engineering geological investigation, topographical survey and statistic analysis, this paper confirms the provenance, accumulation area, maximum transport distance, annual probability of occurrence and four potentially unstable blocks A-D. Rockfall risk for exposed people in Luojiaqinggangling is estimated by the product of three conditional probabilities (annual probability of occurrence, reach probability and temporal-spatial probability) and vulnerability. Based on the rich statistical data of historical rockfall, the annual probability of occurrence is derived from a magnitude-cumulative frequency (MCF) distribution of rockfall events. Considering the size statistical characteristics of the historical rockfall and the position uncertainties of unstable blocks in provenance, this paper conducts the inversion analysis of slope restitution and friction coefficients. It uses the two-dimensional simulation software Rockfall. On these basis, the arrival probabilities of unstable blocks A-D were obtained after numerous random simulation and statistical analysis. Pedestrians and residents that are confirmed as the affected body based on field investigation, temporal-spatial probability depends on the mobility of the exposed elements. It is calculated using empirical equation according to the movement feature of affected body. The vulnerability was determined combining the kinetic energy of rockfall and the location of affected body. According to the product of occurrence probability, arrival probability, temporal distribution probability and vulnerability, the quantitative risk assessment of this rockfall is achieved. The results show that the risk values of block A and D are in a unacceptable risk range, and the risk values of blocks B and C are in a warning range. Those unstable blocks could threaten the life safety of the residents, therefore, it is essential to take appropriate measures for the disaster prevention and mitigation.
2017, 25(2): 531-540.
The northern section of Xiaojiang fault zone is the largest fracture structure in Baihetan hydropower station reservoir. Its characteristics and activities have a clear impact on migration and relocation near the reservoir. After studies of large scale investigation, fault zone quartz morphology scan and radon survey, the distribution characteristics of Xiaojiang fault zone is defined—-from north of Ningnan county, along the left bank of Jinsha River, passing Yongle, Luji, Liugu and extending to the south of Menggu. Quartz micro morphology statistical analysis and stress micro shape show that the fault activity is strong in the late Pleistocene. The facts that there are a quartz grain surface with representatives of the two sliding mode (creep and stick slip) stress micro shape combined, the stress micro shape of corrosion degree, stacking and cutting relationship, show that the fault slipped in the late Pleistocene of at least three sub-periods, at the early stage of the creep, advanced for stick slip. The potential seismic hazard evaluation suggests that possible earthquake magnitude of northern section of Xiaojiang fault zone is MS6.8~MS7.1. Therefore, there may be another strong shock in this area in the future.
The northern section of Xiaojiang fault zone is the largest fracture structure in Baihetan hydropower station reservoir. Its characteristics and activities have a clear impact on migration and relocation near the reservoir. After studies of large scale investigation, fault zone quartz morphology scan and radon survey, the distribution characteristics of Xiaojiang fault zone is defined—-from north of Ningnan county, along the left bank of Jinsha River, passing Yongle, Luji, Liugu and extending to the south of Menggu. Quartz micro morphology statistical analysis and stress micro shape show that the fault activity is strong in the late Pleistocene. The facts that there are a quartz grain surface with representatives of the two sliding mode (creep and stick slip) stress micro shape combined, the stress micro shape of corrosion degree, stacking and cutting relationship, show that the fault slipped in the late Pleistocene of at least three sub-periods, at the early stage of the creep, advanced for stick slip. The potential seismic hazard evaluation suggests that possible earthquake magnitude of northern section of Xiaojiang fault zone is MS6.8~MS7.1. Therefore, there may be another strong shock in this area in the future.
2017, 25(2): 541-546.
Under the influence of weathering, unloading and earthquake, any local instability of natural slope surface above the"opening line" of engineering slope can pose a serious threat to engineering and personnel safety. According to the survey data of hazardous sources of slopes surrounding six important hydropower stations in Western Sichuan, China, the development characteristics and distribution laws of different types of hazardous sources are studied. The results show that under the control of factors of fracture development of down dip and steep dip and strong weathering of fracture type and sandwich type, the rock masses of surrounding slope generate the hazardous sources, such as collapse rock, collapse rock group and dangerous rock mass. It can be found that the volume of hazardous source concentrates upon the range of small and medium size. The hazardous sources are mainly distributed on the surrounding slope with the relative elevation range of 0 to 500m and the development characteristic of dangerous rock mass is vertical zoning, which are intensively distributed on the surrounding slope with the relative elevation scope of 0 to 200m. It also indicates that the surrounding slope gradient of hazardous sources distribution is more than 25°.The quantity of hazardous sources is most when the gradient is ranged from 35°to 40°. The investigation of surrounding slope with the relative elevation scope of 0 to 500m and gradient range of 35°to 75°should be focused and the corresponding prevention measures are adopted on the basis of types and development distribution of hazardous sources.
Under the influence of weathering, unloading and earthquake, any local instability of natural slope surface above the"opening line" of engineering slope can pose a serious threat to engineering and personnel safety. According to the survey data of hazardous sources of slopes surrounding six important hydropower stations in Western Sichuan, China, the development characteristics and distribution laws of different types of hazardous sources are studied. The results show that under the control of factors of fracture development of down dip and steep dip and strong weathering of fracture type and sandwich type, the rock masses of surrounding slope generate the hazardous sources, such as collapse rock, collapse rock group and dangerous rock mass. It can be found that the volume of hazardous source concentrates upon the range of small and medium size. The hazardous sources are mainly distributed on the surrounding slope with the relative elevation range of 0 to 500m and the development characteristic of dangerous rock mass is vertical zoning, which are intensively distributed on the surrounding slope with the relative elevation scope of 0 to 200m. It also indicates that the surrounding slope gradient of hazardous sources distribution is more than 25°.The quantity of hazardous sources is most when the gradient is ranged from 35°to 40°. The investigation of surrounding slope with the relative elevation scope of 0 to 500m and gradient range of 35°to 75°should be focused and the corresponding prevention measures are adopted on the basis of types and development distribution of hazardous sources.
2017, 25(2): 547-555.
The formation and development of bottom undercutting area are one disease of soil sites, which is the most typical and common disease affected by environmental. This paper investigates, monitors and analyses the morphology, salinity, dry-wet conditions and wind field characters of the Great Wall on Ming Dynasty ruins in 12 cities along the Hexi Corridor. It finds that the morphology, salinity, wind field characters and temperature-humidity change in the process of rainfall are significantly different at the site of shady and sunny slopes of the undercutting area. Based on the results of wind tunnel simulation experiment, in which remodeling samples desalinated and mixed with different contents of NaCl and Na2SO4 and undergoing 3, 6, 9, 12 dry-moisture cycles, differential effect in the site of shady and sunny slopes of the undercutting area of earthen ruins in arid region is proposed. It also reveals the influences of salt type and content, number of wet and dry cycles, wind velocity and time of blowing on differential effect. Finally, the formation mechanism of differential effects is discussed with the results of investigation analysis and experiment.
The formation and development of bottom undercutting area are one disease of soil sites, which is the most typical and common disease affected by environmental. This paper investigates, monitors and analyses the morphology, salinity, dry-wet conditions and wind field characters of the Great Wall on Ming Dynasty ruins in 12 cities along the Hexi Corridor. It finds that the morphology, salinity, wind field characters and temperature-humidity change in the process of rainfall are significantly different at the site of shady and sunny slopes of the undercutting area. Based on the results of wind tunnel simulation experiment, in which remodeling samples desalinated and mixed with different contents of NaCl and Na2SO4 and undergoing 3, 6, 9, 12 dry-moisture cycles, differential effect in the site of shady and sunny slopes of the undercutting area of earthen ruins in arid region is proposed. It also reveals the influences of salt type and content, number of wet and dry cycles, wind velocity and time of blowing on differential effect. Finally, the formation mechanism of differential effects is discussed with the results of investigation analysis and experiment.
2017, 25(2): 556-564.
Fractured rock mass slope is one of the most unstable slopes in geological engineering. It has flabby original rock structures, generally open structural planes and poor stability surrounding rocks. The fractured rock mass is exposed discontinuity and the spatial distribution is different. These characteristics lead to the boundary of slope failure is not obvious. It causes deformation and failure mechanism difficult to be determined. As an example of the fractured rock slope of the Lenggu Hydropower Station in the Yalong River, based on geological environment investigation and survey of adit, this paper systematically studies the fractured rock mass structure characteristics, analyzes the boundary conditions which controls the slope deformation and failure, and summarizes the slope deformation and failure modes. Moreover, the UDEC discrete element simulation is used to verify the modes. The results show that the deformation and failure of the rock slope is mainly controlled by rock slope structures and internal relative large structures. The deformation evolution process is divided into three stages: stress adjustment, aging deformation and local instability. The deformation failure modes include fault controlled bottom slip mode and fracture cutting failure mode. At present, there are few relatively studies on the fractured rock slope, lack of large-scale engineering case support. The research results provide reference for the study of this kind of slope in water conservancy project.
Fractured rock mass slope is one of the most unstable slopes in geological engineering. It has flabby original rock structures, generally open structural planes and poor stability surrounding rocks. The fractured rock mass is exposed discontinuity and the spatial distribution is different. These characteristics lead to the boundary of slope failure is not obvious. It causes deformation and failure mechanism difficult to be determined. As an example of the fractured rock slope of the Lenggu Hydropower Station in the Yalong River, based on geological environment investigation and survey of adit, this paper systematically studies the fractured rock mass structure characteristics, analyzes the boundary conditions which controls the slope deformation and failure, and summarizes the slope deformation and failure modes. Moreover, the UDEC discrete element simulation is used to verify the modes. The results show that the deformation and failure of the rock slope is mainly controlled by rock slope structures and internal relative large structures. The deformation evolution process is divided into three stages: stress adjustment, aging deformation and local instability. The deformation failure modes include fault controlled bottom slip mode and fracture cutting failure mode. At present, there are few relatively studies on the fractured rock slope, lack of large-scale engineering case support. The research results provide reference for the study of this kind of slope in water conservancy project.
2017, 25(2): 565-573.
As the constant development of China's economy and population increases, the water shortage is becoming more and more severe. Many regions are now facing water resource crisis. In order to solve this problem and offer a dynamic evaluating scheme, this paper makes qualitative analysis of water resources and separates it into two parts——"supply" and "demand", according to the categories on National Bureau of Statistics of China. And then, it makes more specific categories in each part and uses the data to get fitted graphs and equations. Then, it establishes differential equations and analyzes the collected data to develop a dynamic mathematical model of water resource to assess whether a particular area has the ability to meet the demand of water usage. And we also use past data and facts to test our hypothesis. At last, we choose Beijing as the object of study, use this model to assess the water security level and obtain the future situation of water resource in Beijing in the following 10 years. Beijing is the capital of China, situating in the north of China. It is somehow different because the government is running a "south water to north" plan to help Beijing offer enough water to its citizens. Also, in 2008 Beijing is the host city of the 29th Olympic Games. So this influences the industrial water emission, which we explain in the paper in detail. Based on the analysis, we put forward two policy proposals to solve the problem of water crisis: either to introduce new policy to restrict the water sewage or to increase the water input from other regions.
As the constant development of China's economy and population increases, the water shortage is becoming more and more severe. Many regions are now facing water resource crisis. In order to solve this problem and offer a dynamic evaluating scheme, this paper makes qualitative analysis of water resources and separates it into two parts——"supply" and "demand", according to the categories on National Bureau of Statistics of China. And then, it makes more specific categories in each part and uses the data to get fitted graphs and equations. Then, it establishes differential equations and analyzes the collected data to develop a dynamic mathematical model of water resource to assess whether a particular area has the ability to meet the demand of water usage. And we also use past data and facts to test our hypothesis. At last, we choose Beijing as the object of study, use this model to assess the water security level and obtain the future situation of water resource in Beijing in the following 10 years. Beijing is the capital of China, situating in the north of China. It is somehow different because the government is running a "south water to north" plan to help Beijing offer enough water to its citizens. Also, in 2008 Beijing is the host city of the 29th Olympic Games. So this influences the industrial water emission, which we explain in the paper in detail. Based on the analysis, we put forward two policy proposals to solve the problem of water crisis: either to introduce new policy to restrict the water sewage or to increase the water input from other regions.
2017, 25(2): 424-435.
The precise calculation of landslide volume seems simple but difficult actually. The Loess Plateau has a few characteristics which include sparse vegetation, high degree exposure of rock and soil, and landslide susceptibility. It has occurred many landslides. Compared with the traditional calculation method, such as remote sensing and 3D laser scanning, digital close-range photogrammetry is little affected by all kinds of factors and has the features of flexible operation, high efficiency and high precision products. This paper uses Dangchuan 2# loess landslide in Heifangtai tableland as an example. It uses high resolution close-range photogrammetry data to analyze topography change between pre-sliding and post-sliding. Based on the field investigation and carrying out fine mapping of the landslide, this paper realizes the digital landslide. The detailed study consists of landslide influence, landslide area, landslide volume, loose coefficient of landslide volume and the local dry density change. The results are shown the follows.(1) It covers a total area of 105216m2, with 217m in north-south direction, and 176m in west-east direction. The average thickness of the landslide is about 20m (slip source area), with sliding 782m, trailing 122m in altitude from the landslide crown to landslide top.(2) According to the characteristics of the sliding and accumulation of each part of the slope, it is divided into the collapse zone, the main sliding zone, the sliding zone, the circulation accumulation area, the shovel winding accumulation area, the extrusion and accumulation area, the two accumulation area and the dust accumulation area.(3) According to high resolution DEM, the sliding volume is 31.72×104m3 and accumulating volume is 49.96×104m3. (4) The overall loose coefficient of the landslide is 1.411. The local dry density has great difference, which has close relationship with the development characteristics and the movement process of the landslide.
The precise calculation of landslide volume seems simple but difficult actually. The Loess Plateau has a few characteristics which include sparse vegetation, high degree exposure of rock and soil, and landslide susceptibility. It has occurred many landslides. Compared with the traditional calculation method, such as remote sensing and 3D laser scanning, digital close-range photogrammetry is little affected by all kinds of factors and has the features of flexible operation, high efficiency and high precision products. This paper uses Dangchuan 2# loess landslide in Heifangtai tableland as an example. It uses high resolution close-range photogrammetry data to analyze topography change between pre-sliding and post-sliding. Based on the field investigation and carrying out fine mapping of the landslide, this paper realizes the digital landslide. The detailed study consists of landslide influence, landslide area, landslide volume, loose coefficient of landslide volume and the local dry density change. The results are shown the follows.(1) It covers a total area of 105216m2, with 217m in north-south direction, and 176m in west-east direction. The average thickness of the landslide is about 20m (slip source area), with sliding 782m, trailing 122m in altitude from the landslide crown to landslide top.(2) According to the characteristics of the sliding and accumulation of each part of the slope, it is divided into the collapse zone, the main sliding zone, the sliding zone, the circulation accumulation area, the shovel winding accumulation area, the extrusion and accumulation area, the two accumulation area and the dust accumulation area.(3) According to high resolution DEM, the sliding volume is 31.72×104m3 and accumulating volume is 49.96×104m3. (4) The overall loose coefficient of the landslide is 1.411. The local dry density has great difference, which has close relationship with the development characteristics and the movement process of the landslide.
2017, 25(2): 480-487.
It is important to study the confined groundwater range of action in the translational landslide. It is helpful to accurately evaluate the slope stability, and provides a reasonable guidance for the study on disaster mechanism and disaster prevention of translational landslide. The dip angle of the rock formation is small. The influence of the dip angle is usually neglected in the analysis of the confined groundwater range of action in the translational landslide. Based on the theory of groundwater flow to canals, considering the dip angle, the analysis model of groundwater seepage about the translational landslide is established. A new formula calculating the confined water range of action is deduced. The sensitivity of confined groundwater to the dip angle is analyzed in detail. The concept of the sensitive dip angle is put forward. The calculation results show that the dip angle has significant effect on the confined groundwater range of action. This effect is closely related to the thickness of the permeable layer, the seepage discharge, and the coefficient of permeability. The greater the thickness of the permeable layer, the more significant the dip angle impact on the range of action of confined groundwater. Meanwhile, the sensitive dip angle is influenced by the thickness of the permeable layer, the seepage discharge, the coefficient of permeability and so on. At last, the new model is used to analyze the landslide. The rationality of this new model is verified.
It is important to study the confined groundwater range of action in the translational landslide. It is helpful to accurately evaluate the slope stability, and provides a reasonable guidance for the study on disaster mechanism and disaster prevention of translational landslide. The dip angle of the rock formation is small. The influence of the dip angle is usually neglected in the analysis of the confined groundwater range of action in the translational landslide. Based on the theory of groundwater flow to canals, considering the dip angle, the analysis model of groundwater seepage about the translational landslide is established. A new formula calculating the confined water range of action is deduced. The sensitivity of confined groundwater to the dip angle is analyzed in detail. The concept of the sensitive dip angle is put forward. The calculation results show that the dip angle has significant effect on the confined groundwater range of action. This effect is closely related to the thickness of the permeable layer, the seepage discharge, and the coefficient of permeability. The greater the thickness of the permeable layer, the more significant the dip angle impact on the range of action of confined groundwater. Meanwhile, the sensitive dip angle is influenced by the thickness of the permeable layer, the seepage discharge, the coefficient of permeability and so on. At last, the new model is used to analyze the landslide. The rationality of this new model is verified.
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