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Editor Work2014 Vol. 22, No. 5
Previous Issue
2014, 22(5): 779-784.
Abstract
1381KB
Loess has the collapsibility characteristic. Loess can have the phenomenon of unstability when it is used as foundation materials. The technique of using strengthening materials cushion to improve water stability and strength of loess foundations has been widely applied. In this test, cushions made of lime, fly ash and cement are added into loess separately. The moisture content, density, dry density, Specific Surface Area(SSA) and Cation Exchange Capacity(CEC) of the loess at different places in vertical direction are measured. Results indicate that the lime, fly ash and cement cushion all have considerable impact on the moisture content, density, SSA and CEC of adjacent loess(10～15cm),changing the microstructure and enhance the water stability of the loess. The closer to the cushion, the smaller the moisture content, SSA and CEC are and the greater the density is Lime cushion has the best effect. It can reduce over 4% of the moisture content, increase 1.0～1.5g cm-3 of the loess density. Effects of fly ash are weaker and cement the weakest. Additionally, the SSA and CEC have a linear increment relationship. In the present test, the rate between SSA and CEC of the three tests is controlled between 6.5～7.5.
Loess has the collapsibility characteristic. Loess can have the phenomenon of unstability when it is used as foundation materials. The technique of using strengthening materials cushion to improve water stability and strength of loess foundations has been widely applied. In this test, cushions made of lime, fly ash and cement are added into loess separately. The moisture content, density, dry density, Specific Surface Area(SSA) and Cation Exchange Capacity(CEC) of the loess at different places in vertical direction are measured. Results indicate that the lime, fly ash and cement cushion all have considerable impact on the moisture content, density, SSA and CEC of adjacent loess(10～15cm),changing the microstructure and enhance the water stability of the loess. The closer to the cushion, the smaller the moisture content, SSA and CEC are and the greater the density is Lime cushion has the best effect. It can reduce over 4% of the moisture content, increase 1.0～1.5g cm-3 of the loess density. Effects of fly ash are weaker and cement the weakest. Additionally, the SSA and CEC have a linear increment relationship. In the present test, the rate between SSA and CEC of the three tests is controlled between 6.5～7.5.
2014, 22(5): 785-791.
On the base of the fractal model for bentonite surface, Xu et al.[1] proposed a new method to calculate the swelling deformation of bentonite and expressed as the equation Vw/Vm=KpDs-3(Eq.(1)),which were verified by the experimental data of swelling deformation and swelling pressure of Tsukinuno bentonite, Wyoming bentonite and MX-80 bentonite. Due to the limitation of experiments, two factors to be improved are listed as follows：(1)the fractal dimension obtained from the swelling test was not validated with results of the N2 isotherm adsorption; (2)the expression of the parameter K in Eq.(1)was given on the basis of an empirical equation. In this paper, the surface fractal dimension of Gaomiaozi Na-bentonite and Ca-bentonite, a commercial bentonite and Tsukinuno bentonite are measured using the N2 isotherm adsorption. The swelling deformation is calculated and verified from the above equation using the surface fractal dimension of Gaomiaozi Na-bentonite and Ca-bentonite, a commercial bentonite and Tsukinuno bentonite. Expression of the parameter K in the above equation is deduced from the diffused double layer(DDL)theory.
On the base of the fractal model for bentonite surface, Xu et al.[1] proposed a new method to calculate the swelling deformation of bentonite and expressed as the equation Vw/Vm=KpDs-3(Eq.(1)),which were verified by the experimental data of swelling deformation and swelling pressure of Tsukinuno bentonite, Wyoming bentonite and MX-80 bentonite. Due to the limitation of experiments, two factors to be improved are listed as follows：(1)the fractal dimension obtained from the swelling test was not validated with results of the N2 isotherm adsorption; (2)the expression of the parameter K in Eq.(1)was given on the basis of an empirical equation. In this paper, the surface fractal dimension of Gaomiaozi Na-bentonite and Ca-bentonite, a commercial bentonite and Tsukinuno bentonite are measured using the N2 isotherm adsorption. The swelling deformation is calculated and verified from the above equation using the surface fractal dimension of Gaomiaozi Na-bentonite and Ca-bentonite, a commercial bentonite and Tsukinuno bentonite. Expression of the parameter K in the above equation is deduced from the diffused double layer(DDL)theory.
2014, 22(5): 792-796.
Coarse-grained soils are widely distributed in nature. They have a good compaction performance, including high density, strong water permeability, high shear strength, small settlement. They are not easy to produce liquefaction under the earthquake load. They have been widely used in earth dam construction. On the basis of reviewing a large number of related publications, some advances of the research on the coarse-grained soils are summarized in this paper. They include the shear strength, the deformation behaviors, the stress-strain relationship characteristics and several problems in test. The authors presents some of their own thinking, pointing out the direction of future research on the coarse-grained soils according to the existing knowledge.
Coarse-grained soils are widely distributed in nature. They have a good compaction performance, including high density, strong water permeability, high shear strength, small settlement. They are not easy to produce liquefaction under the earthquake load. They have been widely used in earth dam construction. On the basis of reviewing a large number of related publications, some advances of the research on the coarse-grained soils are summarized in this paper. They include the shear strength, the deformation behaviors, the stress-strain relationship characteristics and several problems in test. The authors presents some of their own thinking, pointing out the direction of future research on the coarse-grained soils according to the existing knowledge.
2014, 22(5): 797-803.
Residual soil from decomposed basalt at Leizhou Peninsula is special regional soil. It has poor physical properties of high liquid limit and large void ratio, good mechanical properties of high strength, and extraordinary properties of strong contractility, humidification and disintegration. This paper attempts to examine the mechanism of the special engineering geological characteristics of the basalt residual soil. It studies the mineral composition, chemical composition, structure, and pore distribution from laboratory tests. Results show that distinct aluminum, iron accumulation, and salt leaching processes occur during the development process of the basalt residual soil. Clay minerals are mainly composed of kaolinite, gibbsite and illite. Furthermore, they are rich in free iron oxide and free aluminum oxide. Microstructure is mainly clot and flocculation structure. The free iron oxide acts as coating that clads particles to form aggregate, which enhances structural strength of soil. Pores mainly consist of denudation pores and micropores in the aggregate and flocculation, and with larger specific surface area and adsorption energy. Large surface tension occurs after immersion which leads to softening and disintegration. Therefore, close attention should be paid to engineering disasters caused by rainfall due to the water sensitive and poor water resistance of the basalt residual soil.
Residual soil from decomposed basalt at Leizhou Peninsula is special regional soil. It has poor physical properties of high liquid limit and large void ratio, good mechanical properties of high strength, and extraordinary properties of strong contractility, humidification and disintegration. This paper attempts to examine the mechanism of the special engineering geological characteristics of the basalt residual soil. It studies the mineral composition, chemical composition, structure, and pore distribution from laboratory tests. Results show that distinct aluminum, iron accumulation, and salt leaching processes occur during the development process of the basalt residual soil. Clay minerals are mainly composed of kaolinite, gibbsite and illite. Furthermore, they are rich in free iron oxide and free aluminum oxide. Microstructure is mainly clot and flocculation structure. The free iron oxide acts as coating that clads particles to form aggregate, which enhances structural strength of soil. Pores mainly consist of denudation pores and micropores in the aggregate and flocculation, and with larger specific surface area and adsorption energy. Large surface tension occurs after immersion which leads to softening and disintegration. Therefore, close attention should be paid to engineering disasters caused by rainfall due to the water sensitive and poor water resistance of the basalt residual soil.
2014, 22(5): 804-810.
This paper reveals the performance of GFRP bolt at earthen sites. It attempts to overcome the limit of bamboo, wood and composite bolt. Furthermore it expands its application on the conservation. GFRP bolts with the diameters of 22mm and 25mm are chosen to do field anchorage experiments. The failure mode and maximum anchorage force are gotten by single and cycle loadings. Meanwhile, the variation and distribution of interface shear strain during the loadings are obtained by adding strain gauges along the bolt-mortar interface. The result shows that mortar-soil interface is the failure interface in both anchorage system, and GFRP bolt with the diameter 22mm can gain the maximum anchoring force of 50kN while GFRP bolt with the diameter 25mm can gain more than 120kN.The interface shear strain attenuates from the loading point to the end of the bolt, with the appearance of compressive strain at some points. Debonding never happens along the interface. In conclusion, GFRP bolt owns huge prospect in conservation of the carriers of earthen sites by replacing composite bolt.
This paper reveals the performance of GFRP bolt at earthen sites. It attempts to overcome the limit of bamboo, wood and composite bolt. Furthermore it expands its application on the conservation. GFRP bolts with the diameters of 22mm and 25mm are chosen to do field anchorage experiments. The failure mode and maximum anchorage force are gotten by single and cycle loadings. Meanwhile, the variation and distribution of interface shear strain during the loadings are obtained by adding strain gauges along the bolt-mortar interface. The result shows that mortar-soil interface is the failure interface in both anchorage system, and GFRP bolt with the diameter 22mm can gain the maximum anchoring force of 50kN while GFRP bolt with the diameter 25mm can gain more than 120kN.The interface shear strain attenuates from the loading point to the end of the bolt, with the appearance of compressive strain at some points. Debonding never happens along the interface. In conclusion, GFRP bolt owns huge prospect in conservation of the carriers of earthen sites by replacing composite bolt.
2014, 22(5): 811-817.
The hydro-mechanical coupling of fractured rock mass is a hot research focus at home and abroad recently. The fractures(or joints) of the rock mass play the main pathways of the fluid flow in fractured rock masses. The apertures of the fractures play an important role in the fluid flow. Both the shear stress-induced dilations and the normal closures or openings induced by normal stress can change the fracture apertures. The permeability of fractured rock mass by taking in account the shear dilation is studied in this paper. It uses the UDEC. The realistic discrete fracture network of sandstone is generated using the joint information from the in-situ survey and the Monte-Carlo Method. The permeability changes of the fracture network rock are simulated by increasing the stress ratio RS(RS=horizontal stress/vertical stress) while keeping the vertical stress constant. The shear dilation of the fractures are considered using the Cloumb slip joint model. The results show that all of the hydraulic apertures, the fluids velocity and the permeability coefficient of the fractured rock mass decrease with the increment of the stress ratio during the stress ratios are enough small(RS is small than 3.1). However, they increase with the increment of stress ratio when the stress ratios are enough large to cause the shear dilation of the fractures(RS is large than 3.1). When the stress ratio is large enough, both the overall permeability and flow patterns are controlled by the fractures which are observed to have shear slipping and dilation phenomenon. During the stress ratio increase from 0.5 to 3.1,the permeability coefficient of the fractured rock masses considering the joint shear dilation is the same to that of disconsidering joint shear dilation. It shows that no shear dilation appears in the fractured rock masses when the stress ratios are enough small. When the stress ratio is more than 3.1,the permeability of rock masses considering the shear dilation increases significantly, but that of disconsidering shear dilation joints decreases slowly. The former is about 2～3 orders of the magnitude more than the latter when the stress ratio exceeds 3.1. The results show that the shear-induced flow channeling has very important impact on the permeability of the fractured rock mass, which shouldn't be neglected.
The hydro-mechanical coupling of fractured rock mass is a hot research focus at home and abroad recently. The fractures(or joints) of the rock mass play the main pathways of the fluid flow in fractured rock masses. The apertures of the fractures play an important role in the fluid flow. Both the shear stress-induced dilations and the normal closures or openings induced by normal stress can change the fracture apertures. The permeability of fractured rock mass by taking in account the shear dilation is studied in this paper. It uses the UDEC. The realistic discrete fracture network of sandstone is generated using the joint information from the in-situ survey and the Monte-Carlo Method. The permeability changes of the fracture network rock are simulated by increasing the stress ratio RS(RS=horizontal stress/vertical stress) while keeping the vertical stress constant. The shear dilation of the fractures are considered using the Cloumb slip joint model. The results show that all of the hydraulic apertures, the fluids velocity and the permeability coefficient of the fractured rock mass decrease with the increment of the stress ratio during the stress ratios are enough small(RS is small than 3.1). However, they increase with the increment of stress ratio when the stress ratios are enough large to cause the shear dilation of the fractures(RS is large than 3.1). When the stress ratio is large enough, both the overall permeability and flow patterns are controlled by the fractures which are observed to have shear slipping and dilation phenomenon. During the stress ratio increase from 0.5 to 3.1,the permeability coefficient of the fractured rock masses considering the joint shear dilation is the same to that of disconsidering joint shear dilation. It shows that no shear dilation appears in the fractured rock masses when the stress ratios are enough small. When the stress ratio is more than 3.1,the permeability of rock masses considering the shear dilation increases significantly, but that of disconsidering shear dilation joints decreases slowly. The former is about 2～3 orders of the magnitude more than the latter when the stress ratio exceeds 3.1. The results show that the shear-induced flow channeling has very important impact on the permeability of the fractured rock mass, which shouldn't be neglected.
2014, 22(5): 818-823.
Study on the structural strength of soil is significant to the understanding of the soil cracking process and preventing related engineering geological problems. This paper takes the Xiashu soil in Nanjing as the object and uses the Super-Mini-Penetration(SMP)test. It analyzes the evolution characteristics of the structural strength of specimens during the drying process. The results show that the SMP test method is a better way for the quantitative study of structural strength of soil during the drying process. This method has the advantages of simple operation, high precision and a wide range of moisture content. During the drying process, the structural strength of specimen section remains stable and its spatial difference is very small in the high moisture content range(w24.27%).In the relative low water content range(w24.27%),the spatial difference of soil structural strength become more evident. As the penetration depth increase, the structural strength decreases and gradually become stable. The soil penetration stress increases exponentially as the average moisture content decreases, which is mainly due to the increase of soil suction caused by the soil water evaporation and the enhancement of interaction force among soil particles. In addition, the decrease of pore ratio and the increase of the soil particle joint point due to the shrinkage deformation of soil will also contribute to enhance the structural strength of clayey soil.
Study on the structural strength of soil is significant to the understanding of the soil cracking process and preventing related engineering geological problems. This paper takes the Xiashu soil in Nanjing as the object and uses the Super-Mini-Penetration(SMP)test. It analyzes the evolution characteristics of the structural strength of specimens during the drying process. The results show that the SMP test method is a better way for the quantitative study of structural strength of soil during the drying process. This method has the advantages of simple operation, high precision and a wide range of moisture content. During the drying process, the structural strength of specimen section remains stable and its spatial difference is very small in the high moisture content range(w24.27%).In the relative low water content range(w24.27%),the spatial difference of soil structural strength become more evident. As the penetration depth increase, the structural strength decreases and gradually become stable. The soil penetration stress increases exponentially as the average moisture content decreases, which is mainly due to the increase of soil suction caused by the soil water evaporation and the enhancement of interaction force among soil particles. In addition, the decrease of pore ratio and the increase of the soil particle joint point due to the shrinkage deformation of soil will also contribute to enhance the structural strength of clayey soil.
2014, 22(5): 824-831.
Qingdao is the typical granite region, which uses the drill and blast method to the excavate tunnel. Firstly, the article analyzes the measured blasting data of 3 work site which belong to Qingdao Metro Line 3 using field measurement and statistical analysis. The correlation between vibration velocity of surface and neighboring buildings and the frequency characteristics caused by blasting of blasting distance and dose were researched. The empirical formula including the above factors was concluded by regression analysis. The numerical modeling method was used to research the influence of blast to surface and neighboring buildings, and the simulate particle vibration data was compared with the measured by numerical simulation. The main conclusions are as follows：(1)with the increase of blasting distance, the maximum vibration velocity of surface particle decreases in the form of index attenuation.(2)the vibration frequency caused by blasting is distributing randomly with scaled distance, therefore it is unable to establish the mathematical model between them, and the dominant frequency mostly ranges from 20 to 70 Hz.(3)with the stories increase, the maximum vibration velocity of three-vectors has the magnifying trend. The maximum vibration velocity of the particle inside the building is generally less than the particle closing to the building exterior surface.
Qingdao is the typical granite region, which uses the drill and blast method to the excavate tunnel. Firstly, the article analyzes the measured blasting data of 3 work site which belong to Qingdao Metro Line 3 using field measurement and statistical analysis. The correlation between vibration velocity of surface and neighboring buildings and the frequency characteristics caused by blasting of blasting distance and dose were researched. The empirical formula including the above factors was concluded by regression analysis. The numerical modeling method was used to research the influence of blast to surface and neighboring buildings, and the simulate particle vibration data was compared with the measured by numerical simulation. The main conclusions are as follows：(1)with the increase of blasting distance, the maximum vibration velocity of surface particle decreases in the form of index attenuation.(2)the vibration frequency caused by blasting is distributing randomly with scaled distance, therefore it is unable to establish the mathematical model between them, and the dominant frequency mostly ranges from 20 to 70 Hz.(3)with the stories increase, the maximum vibration velocity of three-vectors has the magnifying trend. The maximum vibration velocity of the particle inside the building is generally less than the particle closing to the building exterior surface.
2014, 22(5): 832-838.
This paper carries out comparative test study between fully softened strength and residual strength. It is to solve the selection problem of the strength parameters of the resurgent and creeping loess landslides. It takes the typical soils of Shanxi province as the research objects and uses the preloading consolidation method to prepare the saturated remolded samples for repeated direct shear test in order to get the parameters of fully softened strength and residual strength. The test results show that the fully softened strength of loess has such special characteristics that its cohesive force is almost equal to zero and its particles have no directional arrangement. The fully softened strength is closely related to the secondary consolidation stress and the clay particle content of the sample. The stress-strain curve of the sample under secondary consolidation stress less than 300kPa is strain softening model which means fully softened strength is greater than residual strength. The samples with higher clay particle contents have more obvious strain softening appearance than the lower ones. The stress-strain curve of the sample under secondary consolidation stress greater than or equal to 300kPa is the ideal plastic model which means fully softened strength is approximately equal to residual strength. The difference between the fully softened friction angle and the residual friction angle has close relationships with the secondary consolidation stress, the preloading consolidation stress and the clay particle content of the sample. The difference between the fully softened friction angle and the residual friction angle decreases with the increasing of the secondary consolidation stress, eventually, tends to be equal to 0.When the preloading consolidation stress is less than 300kPa, the difference between the two friction angles and the effect of the clay particle contents on them appear power law increasing with the decreasing of preloading consolidation stress. When the preloading consolidation stress is greater than or equal to 300kPa, the fully softened strength is approximately equal to residual strength and its parameters can approximately replace the parameters of residual strength. The research results supply a reference to the selection of the strength parameters used in the stability analysis for the resurgent and creeping loess landslides.
This paper carries out comparative test study between fully softened strength and residual strength. It is to solve the selection problem of the strength parameters of the resurgent and creeping loess landslides. It takes the typical soils of Shanxi province as the research objects and uses the preloading consolidation method to prepare the saturated remolded samples for repeated direct shear test in order to get the parameters of fully softened strength and residual strength. The test results show that the fully softened strength of loess has such special characteristics that its cohesive force is almost equal to zero and its particles have no directional arrangement. The fully softened strength is closely related to the secondary consolidation stress and the clay particle content of the sample. The stress-strain curve of the sample under secondary consolidation stress less than 300kPa is strain softening model which means fully softened strength is greater than residual strength. The samples with higher clay particle contents have more obvious strain softening appearance than the lower ones. The stress-strain curve of the sample under secondary consolidation stress greater than or equal to 300kPa is the ideal plastic model which means fully softened strength is approximately equal to residual strength. The difference between the fully softened friction angle and the residual friction angle has close relationships with the secondary consolidation stress, the preloading consolidation stress and the clay particle content of the sample. The difference between the fully softened friction angle and the residual friction angle decreases with the increasing of the secondary consolidation stress, eventually, tends to be equal to 0.When the preloading consolidation stress is less than 300kPa, the difference between the two friction angles and the effect of the clay particle contents on them appear power law increasing with the decreasing of preloading consolidation stress. When the preloading consolidation stress is greater than or equal to 300kPa, the fully softened strength is approximately equal to residual strength and its parameters can approximately replace the parameters of residual strength. The research results supply a reference to the selection of the strength parameters used in the stability analysis for the resurgent and creeping loess landslides.
2014, 22(5): 839-844.
The saturation and consolidation status of soil samples is very important in the triaxial test of saturated loess. The vacuum saturation is a common effective way to saturate samples in the test. It is very difficult to saturate the remoulded loess samples by vacuum saturation which may destroy the structure of remoulded loess. So the remoulded loess samples have to be saturated on the triaxial apparatus. A number of saturation tests and consolidation tests are carried on the unsaturated triaxial apparatus of GDS for remoulded loess at Lanzhou. A tee-joint is installed on the triaxial apparetus to cut down the time of saturation test and consolidation test. Also it is a better way to simulate the soils in natural state through up and down to saturate and consolidate. This work contributes to the saturation and consolidation of silty clay in the triaxial test.
The saturation and consolidation status of soil samples is very important in the triaxial test of saturated loess. The vacuum saturation is a common effective way to saturate samples in the test. It is very difficult to saturate the remoulded loess samples by vacuum saturation which may destroy the structure of remoulded loess. So the remoulded loess samples have to be saturated on the triaxial apparatus. A number of saturation tests and consolidation tests are carried on the unsaturated triaxial apparatus of GDS for remoulded loess at Lanzhou. A tee-joint is installed on the triaxial apparetus to cut down the time of saturation test and consolidation test. Also it is a better way to simulate the soils in natural state through up and down to saturate and consolidate. This work contributes to the saturation and consolidation of silty clay in the triaxial test.
2014, 22(5): 845-850.
The frequent occurring landslides and more than 3m subsidence at Hefangtai are caused by long-term irrigation in Linxia city, Gansu province. This paper analyzes the microstructure nature of the loess collected from top and bottom of Heifangtai. The consolidation test with increasing water content and mercury intrusion porosimetry are conducted on the loess samples in this paper. The loess at the top of the platform is characterized by loose particle, packing with bigger porosity. The clay content is lower. The loess at the bottom of the platform, however, processes relatively tight arrangement of the particles with less porosity, and higher clay content. In the consolidation test, the void ratio falls sharply. The microstructure strength of the loess reduces suddenly or loss when 21% water content. This abrupt change in bottom loess does not occur, which indicates relatedly weak water sensitivity. The pore diameter compression interval of the top loess is 100m. The 5～20m. The compression interval of the bottom loess is 100m and 1～10m. However, the volume of the pore,0.1m, increases as the water content increases.
The frequent occurring landslides and more than 3m subsidence at Hefangtai are caused by long-term irrigation in Linxia city, Gansu province. This paper analyzes the microstructure nature of the loess collected from top and bottom of Heifangtai. The consolidation test with increasing water content and mercury intrusion porosimetry are conducted on the loess samples in this paper. The loess at the top of the platform is characterized by loose particle, packing with bigger porosity. The clay content is lower. The loess at the bottom of the platform, however, processes relatively tight arrangement of the particles with less porosity, and higher clay content. In the consolidation test, the void ratio falls sharply. The microstructure strength of the loess reduces suddenly or loss when 21% water content. This abrupt change in bottom loess does not occur, which indicates relatedly weak water sensitivity. The pore diameter compression interval of the top loess is 100m. The 5～20m. The compression interval of the bottom loess is 100m and 1～10m. However, the volume of the pore,0.1m, increases as the water content increases.
2014, 22(5): 851-854.
The photoelasticity technique can remove the particles basal friction by using density matched. It can be used to study the meso-deformation characteristics of the granular stuff. In this paper, the simple shear photoelasitc experiment is conducted on the granular system with 82% packing fraction. The research results indicate that the direction of force chain(or principle stress) is the relatively short diagonal line direction of the shear box, and cross over the whole granular system. The force chain is disappeared on the boundary of the shear box to get the balancing of stresses status. The normalized deformation vector of the granular materials shows symmetrical in the shear box axial.
The photoelasticity technique can remove the particles basal friction by using density matched. It can be used to study the meso-deformation characteristics of the granular stuff. In this paper, the simple shear photoelasitc experiment is conducted on the granular system with 82% packing fraction. The research results indicate that the direction of force chain(or principle stress) is the relatively short diagonal line direction of the shear box, and cross over the whole granular system. The force chain is disappeared on the boundary of the shear box to get the balancing of stresses status. The normalized deformation vector of the granular materials shows symmetrical in the shear box axial.
2014, 22(5): 855-860.
In recent years, the application of distributed optical fiber sensing(DOFS)technologies to geo-engineering monitoring has been a research focus. But in engineering practices, the deformation compatibility between the embedded sensing optical fibers and the soil and rock masses can significantly affect the monitoring results, which is the main barrier for the DFOS based engineering monitoring. This paper is based on a series of laboratory pullout tests on the three types of the single-mode optical fibers embedded in sand. The comparisons between the pullout force-pullout displacement curves of these fibers under different overburden pressures are conducted. A tri-linear pullout model is established to describe the fiber-sand interfacial mechanical characteristics. Using this model, the variations of the four model parameters, i.e.peak pullout force, residual pullout force, effective pullout displacement and residual pullout displacement, are analyzed considering the influence of overburden pressure. The analysis results indicate the mechanical properties of fiber-sand interface and stress-transfer mechanism, which provides valuable references for the application of the distributed optical fiber optic sensing to soil deformation monitoring, especially in terms of selection criterion of the deformation sensing fiber.
In recent years, the application of distributed optical fiber sensing(DOFS)technologies to geo-engineering monitoring has been a research focus. But in engineering practices, the deformation compatibility between the embedded sensing optical fibers and the soil and rock masses can significantly affect the monitoring results, which is the main barrier for the DFOS based engineering monitoring. This paper is based on a series of laboratory pullout tests on the three types of the single-mode optical fibers embedded in sand. The comparisons between the pullout force-pullout displacement curves of these fibers under different overburden pressures are conducted. A tri-linear pullout model is established to describe the fiber-sand interfacial mechanical characteristics. Using this model, the variations of the four model parameters, i.e.peak pullout force, residual pullout force, effective pullout displacement and residual pullout displacement, are analyzed considering the influence of overburden pressure. The analysis results indicate the mechanical properties of fiber-sand interface and stress-transfer mechanism, which provides valuable references for the application of the distributed optical fiber optic sensing to soil deformation monitoring, especially in terms of selection criterion of the deformation sensing fiber.
2014, 22(5): 861-868.
On April 20, 2013, a strong earthquake of MS 7.0 struck the Lushan County, Sichuan Province, China. Because of the complex terrain conditions of the local area, the strong earthquake triggered numbers of secondary geological disasters, such as landslides, collapses, and debris flows. The Baosheng country, seriously attacked by slope mass movement disasters, was taken as an example for the study area in the paper. The combination of the remote sensing images and the DEM is used for visual interpretation. To evaluate and modify the accuracy of the visualization result, the spectral information and gradient information are then utilized. Moreover, the technology of spatial analysis and statistical analysis method is applied to the analysis of regularity of landslide mechanism, including topography, lithology, geological structure, and seismic intensity. The results show that the slopes of the earthquake-induced landslides are mainly concentrated in the range of 30～50,developed primarily in Mingshan group of earlier-Tertiary strata and Guankou group of Cretaceous composed of siltstone, mudstone and conglomerate, and mainly in the area of intensity Ⅸ.
On April 20, 2013, a strong earthquake of MS 7.0 struck the Lushan County, Sichuan Province, China. Because of the complex terrain conditions of the local area, the strong earthquake triggered numbers of secondary geological disasters, such as landslides, collapses, and debris flows. The Baosheng country, seriously attacked by slope mass movement disasters, was taken as an example for the study area in the paper. The combination of the remote sensing images and the DEM is used for visual interpretation. To evaluate and modify the accuracy of the visualization result, the spectral information and gradient information are then utilized. Moreover, the technology of spatial analysis and statistical analysis method is applied to the analysis of regularity of landslide mechanism, including topography, lithology, geological structure, and seismic intensity. The results show that the slopes of the earthquake-induced landslides are mainly concentrated in the range of 30～50,developed primarily in Mingshan group of earlier-Tertiary strata and Guankou group of Cretaceous composed of siltstone, mudstone and conglomerate, and mainly in the area of intensity Ⅸ.
2014, 22(5): 869-875.
Many landslides in the Three Gorges Reservoir area have large deformation during the drawdown of reservoir water level every year. In order to study the dynamic deformation mechanism, stability and development trend of landslide during drawdown of reservoir water level, this paper takes Baishuihe landslide as an example. Based on the field geological survey, detailed geological exploration, and full use of monitoring data of more than ten years, the deformation characteristics, mechanism, influence factors and stability of landslide are analyzed in detail, and the deformation trend of landslide is predicted. Analysis results show that, during the drawdown of reservoir water level, underground water can not be discharged in time due to the landslide soil permeability is poor. Because decline speed of groundwater is much slower than that of reservoir water, increasing the seepage force in the landslide body apparently, and then further reduces the slope stability. The landslide deformation rate increases with the increasing of decline speed of reservoir water level, and the landslide deformation shows dynamic characteristic of step type.
Many landslides in the Three Gorges Reservoir area have large deformation during the drawdown of reservoir water level every year. In order to study the dynamic deformation mechanism, stability and development trend of landslide during drawdown of reservoir water level, this paper takes Baishuihe landslide as an example. Based on the field geological survey, detailed geological exploration, and full use of monitoring data of more than ten years, the deformation characteristics, mechanism, influence factors and stability of landslide are analyzed in detail, and the deformation trend of landslide is predicted. Analysis results show that, during the drawdown of reservoir water level, underground water can not be discharged in time due to the landslide soil permeability is poor. Because decline speed of groundwater is much slower than that of reservoir water, increasing the seepage force in the landslide body apparently, and then further reduces the slope stability. The landslide deformation rate increases with the increasing of decline speed of reservoir water level, and the landslide deformation shows dynamic characteristic of step type.
2014, 22(5): 876-882.
Numerous wading landslides formed in Three Gorges Reservoir. Water level cyclical fluctuations causes the changes of properties of the rock-soil bank landslides, also make the changes of seepage field and the stability of the landslides. This paper studies the response of the wading landslides stability induced by water level fluctuation. It analyses the hydrodynamic pressure landslide using the classification of significant wading landslide in Three Gorges Reservoir. It takes the Zigui Shuping Landslide as a case study. The SEEP and SLOPE modules Geo-studio software are used to model the process of seepage field and calculate the stability, analyzes the law of effect hydrodynamic pressure landslide under different permeability coefficients of the landslide and the water level rate. The results show that the groundwater level has a concave phenomenon and the stability coefficient increases when the reservoir water level rises. The groundwater level has a convex phenomenon and the stability coefficient obvious decreases when the reservoir water level reduces for hydrodynamic pressure landslide. The reservoir water level fluctuation has the larger rate, and the permeability coefficient is smaller. The reservoir water level fluctuation has more obvious effect on the seepage and stability of the landslide.
Numerous wading landslides formed in Three Gorges Reservoir. Water level cyclical fluctuations causes the changes of properties of the rock-soil bank landslides, also make the changes of seepage field and the stability of the landslides. This paper studies the response of the wading landslides stability induced by water level fluctuation. It analyses the hydrodynamic pressure landslide using the classification of significant wading landslide in Three Gorges Reservoir. It takes the Zigui Shuping Landslide as a case study. The SEEP and SLOPE modules Geo-studio software are used to model the process of seepage field and calculate the stability, analyzes the law of effect hydrodynamic pressure landslide under different permeability coefficients of the landslide and the water level rate. The results show that the groundwater level has a concave phenomenon and the stability coefficient increases when the reservoir water level rises. The groundwater level has a convex phenomenon and the stability coefficient obvious decreases when the reservoir water level reduces for hydrodynamic pressure landslide. The reservoir water level fluctuation has the larger rate, and the permeability coefficient is smaller. The reservoir water level fluctuation has more obvious effect on the seepage and stability of the landslide.
2014, 22(5): 883-889.
This paper analyzes the engineering geological conditions and deformation failure characteristics of Xiangshuping landslide in Dejiang county, Guizhou. It establishes the evolved conceptual model of interbedded of soft and hard low-angle rock stratum that trends outside high slope. Its formation process can be summarized as the three stages of valley formation, namely：time-dependent deformation, sliding-stepwise cracking and sliding-bending-shear break. The instability mechanism and process of slope are reappeared through the numerical analysis of valley evolution and slope failure process. The effect of the interbedded of soft and hard layer on the slope evolution is quantitatively analyzed. The conclusion is that the limitation of the hard rock layer on the deformation of soft rock layer makes it hard for slope body to entirely failure. However, the soft rock continuing to creep can lead to a significant increase in the accumulative internal energy and expansion in local deformation. This process is the cause for instability and failure of the overall slope.
This paper analyzes the engineering geological conditions and deformation failure characteristics of Xiangshuping landslide in Dejiang county, Guizhou. It establishes the evolved conceptual model of interbedded of soft and hard low-angle rock stratum that trends outside high slope. Its formation process can be summarized as the three stages of valley formation, namely：time-dependent deformation, sliding-stepwise cracking and sliding-bending-shear break. The instability mechanism and process of slope are reappeared through the numerical analysis of valley evolution and slope failure process. The effect of the interbedded of soft and hard layer on the slope evolution is quantitatively analyzed. The conclusion is that the limitation of the hard rock layer on the deformation of soft rock layer makes it hard for slope body to entirely failure. However, the soft rock continuing to creep can lead to a significant increase in the accumulative internal energy and expansion in local deformation. This process is the cause for instability and failure of the overall slope.
2014, 22(5): 890-895.
The Dongfeng loess landslide on the south platform in Jing Yang is a typical type of high-speed long distant landslides, induced by the long-term irrigation at the top tableland of the slope. After field investigation, loess samples are taken in different parts of the slope. The intact samples taken in the central slope(Q2) are utilized to do the CU tests, and the ones taken in the slope bottom(Q1) are saturated and then used to conduct the CU tests. Results show that both the unsaturated loess Q2 and the saturated loess Q1 display significantly stress decrease. However, they have different reasons. For the former is caused by the decline of structure strength, while the latter is caused by the pore water pressure generated during the shearing process. All above reveal that once the slope failure occurs, there will be high initiating speed. The ring shear tests are conducted on the sand on the first terrace out of the slope toe to obtain the effective residual friction angle. Then according to the situation of water contents, pore pressure coefficients in different parts are obtained. Then the landslide movement process can be simulated by Sassas landslide motion model,which can show the speed changes and the coverage of landslide. The simulation results are in good agreement with the measures results. The highest speed can reach 37m s-1,also revealing that it is a high speed landslide. The loess landslide with high initial velocity down to the slope foot in the saturate sand layer of the first terraces and liquefaction in the sand layer is the main factor of its remote movement.
The Dongfeng loess landslide on the south platform in Jing Yang is a typical type of high-speed long distant landslides, induced by the long-term irrigation at the top tableland of the slope. After field investigation, loess samples are taken in different parts of the slope. The intact samples taken in the central slope(Q2) are utilized to do the CU tests, and the ones taken in the slope bottom(Q1) are saturated and then used to conduct the CU tests. Results show that both the unsaturated loess Q2 and the saturated loess Q1 display significantly stress decrease. However, they have different reasons. For the former is caused by the decline of structure strength, while the latter is caused by the pore water pressure generated during the shearing process. All above reveal that once the slope failure occurs, there will be high initiating speed. The ring shear tests are conducted on the sand on the first terrace out of the slope toe to obtain the effective residual friction angle. Then according to the situation of water contents, pore pressure coefficients in different parts are obtained. Then the landslide movement process can be simulated by Sassas landslide motion model,which can show the speed changes and the coverage of landslide. The simulation results are in good agreement with the measures results. The highest speed can reach 37m s-1,also revealing that it is a high speed landslide. The loess landslide with high initial velocity down to the slope foot in the saturate sand layer of the first terraces and liquefaction in the sand layer is the main factor of its remote movement.
2014, 22(5): 896-902.
The failure of slopes composed of metamorphic schist is closely related to the combination of structural planes and slope surfaces. The block theory is outstanding in the field of analyzing the combination of structural planes and slope surfaces. The paper takes the slopes along the State Road 108 in Heihe reservoir for example and explains the method of analyzing slope stability in metamorphic schist zone with the block theory. As a preparation, the paper designs a program about the block theory and a program about the isopycnic graph of structure plane. Through the site investigation of slopes along the State Road 108 in Heihe reservoir, the slopes are divided into 15 sections and 4 of them are potential rockfall sections. This paper selects one typical point in each of the potential rockfall sections. At each point, we find out the movable block, the key block and the residual sliding force by the block theory and the self-compiling program. The combination of the structure planes of the calculated key blocks is identical to that of the fact. The results of the residual sliding force show that three of them are of high risk of rockfalls, and need engineering measures to prevent landslides from blocking the State Road 108. The paper explains the method of analyzing slope stability in metamorphic schist zone with the block theory, which has special reference to some other engineering projects.
The failure of slopes composed of metamorphic schist is closely related to the combination of structural planes and slope surfaces. The block theory is outstanding in the field of analyzing the combination of structural planes and slope surfaces. The paper takes the slopes along the State Road 108 in Heihe reservoir for example and explains the method of analyzing slope stability in metamorphic schist zone with the block theory. As a preparation, the paper designs a program about the block theory and a program about the isopycnic graph of structure plane. Through the site investigation of slopes along the State Road 108 in Heihe reservoir, the slopes are divided into 15 sections and 4 of them are potential rockfall sections. This paper selects one typical point in each of the potential rockfall sections. At each point, we find out the movable block, the key block and the residual sliding force by the block theory and the self-compiling program. The combination of the structure planes of the calculated key blocks is identical to that of the fact. The results of the residual sliding force show that three of them are of high risk of rockfalls, and need engineering measures to prevent landslides from blocking the State Road 108. The paper explains the method of analyzing slope stability in metamorphic schist zone with the block theory, which has special reference to some other engineering projects.
2014, 22(5): 903-914.
The prediction of rockburst is a great challenge for the construction of underground engineering. We take a tunnel in southwest China as a case study. We consider the three conditions inducing rockburst as：rockburst occurring probability of rock mass, the integrity of rock mass and the high in-situ stress. We take the maximum stored elastic strain energy(Es) and the rock brittleness modulus(B) as the indicators. We then analyze the rockburst occurring probability of quartz sandstone and limestone in the deep tunnel. Based on the collected in-situ stress data we collected, with the assistance of finite element method which immediately simulates the geological process, we launch a back analysis on the stress field of the rock mass in the tunnel area and consequently obtain the high in-situ stress-section in the area. Utilizing field sampling tests, we study the physical and mechanical properties of the wall rocks like the uniaxial compressive strength of intact rock. We summarize the previous rockburst predicting methods, employ the comprehensive engineering geological analysis, elaborate the conditions causing tunnel rockburst. Then, we use the theory of rock mass mechanics, the non-linear science as guidance, the geological comprehensive analysis method and the stress intensity ratio method to predict the location and intensity of rockburst that may occur in the tunnel area.
The prediction of rockburst is a great challenge for the construction of underground engineering. We take a tunnel in southwest China as a case study. We consider the three conditions inducing rockburst as：rockburst occurring probability of rock mass, the integrity of rock mass and the high in-situ stress. We take the maximum stored elastic strain energy(Es) and the rock brittleness modulus(B) as the indicators. We then analyze the rockburst occurring probability of quartz sandstone and limestone in the deep tunnel. Based on the collected in-situ stress data we collected, with the assistance of finite element method which immediately simulates the geological process, we launch a back analysis on the stress field of the rock mass in the tunnel area and consequently obtain the high in-situ stress-section in the area. Utilizing field sampling tests, we study the physical and mechanical properties of the wall rocks like the uniaxial compressive strength of intact rock. We summarize the previous rockburst predicting methods, employ the comprehensive engineering geological analysis, elaborate the conditions causing tunnel rockburst. Then, we use the theory of rock mass mechanics, the non-linear science as guidance, the geological comprehensive analysis method and the stress intensity ratio method to predict the location and intensity of rockburst that may occur in the tunnel area.
2014, 22(5): 915-920.
The are two factors controlling the deformation and failure of slope. One factor is the stress redistribution caused by excavation or loading; the other is variation of shear strength caused by surface water infiltration or groundwater level. Most of the cut loess slopes are above the groundwater level. After excavation, the stress condition does not change much. If no irrigation exsits, the failure of slope is attributed to reduction of shear strength caused by rainfall. The traditional principle of effective stress is not suitable for the strength formula of Mohr-Coulomb because of the negative pore water pressure in unsaturated soils. The Bishops effective stress principle is also useless for its hard-measuring parameters and immature technology. It is worth discussing to determine the shear strength parameters based on the traditional test. The Jijiayuan loess landslide beside the G206 highway as a cut slope is applied to determine the strength parameters c and using the Bishop inverse analysis. Quick direct shear test is used to get the parameters under different moisture contents. Comparing the test result with the inverse result, it is found that they are almost the same when the moisture content is close to the plastic limit. Given that the plastic limit expresses the states of the soil, and when the moisture content exceeds the value to the plastic state, the strength of the soil decreases obviously, leading to failure, which conforms to the consistency and strength principle of the soil. So it is suggested that the shear strength parameters measured by quick direct shear under plastic limit can be applied to the slope stability assessment.
The are two factors controlling the deformation and failure of slope. One factor is the stress redistribution caused by excavation or loading; the other is variation of shear strength caused by surface water infiltration or groundwater level. Most of the cut loess slopes are above the groundwater level. After excavation, the stress condition does not change much. If no irrigation exsits, the failure of slope is attributed to reduction of shear strength caused by rainfall. The traditional principle of effective stress is not suitable for the strength formula of Mohr-Coulomb because of the negative pore water pressure in unsaturated soils. The Bishops effective stress principle is also useless for its hard-measuring parameters and immature technology. It is worth discussing to determine the shear strength parameters based on the traditional test. The Jijiayuan loess landslide beside the G206 highway as a cut slope is applied to determine the strength parameters c and using the Bishop inverse analysis. Quick direct shear test is used to get the parameters under different moisture contents. Comparing the test result with the inverse result, it is found that they are almost the same when the moisture content is close to the plastic limit. Given that the plastic limit expresses the states of the soil, and when the moisture content exceeds the value to the plastic state, the strength of the soil decreases obviously, leading to failure, which conforms to the consistency and strength principle of the soil. So it is suggested that the shear strength parameters measured by quick direct shear under plastic limit can be applied to the slope stability assessment.
2014, 22(5): 921-927.
The Karakorum highway is easy to develop geo-hazards. Early recognition of the tiny deformation is an efficient measure to prevent the geo-hazards. Setting the road along the Gonggeer-Mushitage Mountain section as the study area, this paper selects the 16 scenes of PALSAR data during 4 years and uses the SBAS-InSAR technology to measure the deformation along the highway. The geological setting analysis is also used. The following five results are obtained：(1)the glacier movement and glacial debris flows are the main geo-hazards along the highway. Their large deformation is easy to identify. The effective PS(Persistent Scatter) points are mainly distributed in glacial till section showing as the positive and negative larger deformation interphase points group. The glacier till impacting the road is well developed in the Gonggeer-Mushitage Mountain region.(2)There are mostly the bedding slope rock masses with weathering seriously, lacking of stability and easy to form slip rock along the highway, which demonstrates the negative deformation.(3)In the wide valley area, the value of PS points deformation velocities are mainly with the positive abnormal and smaller negative. The region is consisted of diluvium with the glacier till under. The glacier melt water supply is adequate. The soil moisture content is higher, which may lead to frost heave. At the same time there are likely to be the deformation in direction of the slope gradient of gravity. Both deformations composited in SBAS-InSAR measurements are mainly showed as the positive abnormal of LOS deformation.(4)the highway mainly distributes along the lake and on the glacier debris flow alluvial fans. It is supposed that the deformation of uneven distribution of soft soil causes some parts of the highway relatively sinking.(5)SBAS-InSAR high-precision deformation observation with wide area coverage shows that it is effective on quickly identification of the large linear engineering geological stability.
The Karakorum highway is easy to develop geo-hazards. Early recognition of the tiny deformation is an efficient measure to prevent the geo-hazards. Setting the road along the Gonggeer-Mushitage Mountain section as the study area, this paper selects the 16 scenes of PALSAR data during 4 years and uses the SBAS-InSAR technology to measure the deformation along the highway. The geological setting analysis is also used. The following five results are obtained：(1)the glacier movement and glacial debris flows are the main geo-hazards along the highway. Their large deformation is easy to identify. The effective PS(Persistent Scatter) points are mainly distributed in glacial till section showing as the positive and negative larger deformation interphase points group. The glacier till impacting the road is well developed in the Gonggeer-Mushitage Mountain region.(2)There are mostly the bedding slope rock masses with weathering seriously, lacking of stability and easy to form slip rock along the highway, which demonstrates the negative deformation.(3)In the wide valley area, the value of PS points deformation velocities are mainly with the positive abnormal and smaller negative. The region is consisted of diluvium with the glacier till under. The glacier melt water supply is adequate. The soil moisture content is higher, which may lead to frost heave. At the same time there are likely to be the deformation in direction of the slope gradient of gravity. Both deformations composited in SBAS-InSAR measurements are mainly showed as the positive abnormal of LOS deformation.(4)the highway mainly distributes along the lake and on the glacier debris flow alluvial fans. It is supposed that the deformation of uneven distribution of soft soil causes some parts of the highway relatively sinking.(5)SBAS-InSAR high-precision deformation observation with wide area coverage shows that it is effective on quickly identification of the large linear engineering geological stability.
2014, 22(5): 928-935.
The Hou gully in Shimian County is a typical debris-flow gully where either natural debris flow or mine debris flow can occur. This paper is based on the investigation and analysis on the deposition characteristics of former natural debris flows in history, mine debris flows since exploitation of mineral resource in recent years and the combined debris flow occurred on July 4, 2013. The combined effect of natural debris flow and mine debris flow is summarized in the following five aspects：(1)the multi effect of the solid materials supplying for debris flow,(2)the reversal effects of debris flow development and evolution,(3)the complex effect in debris flow initiation and occurrence process,(4)the amplification effect in debris flow downstream transporting process and (5)the chain effect during debris flow damaging process. In addition, prevention countermeasures are put forward for the Hou gully debris flow at the end of this paper. It is suggested that the control works built at the middle stream for the blocking of natural debris flow can play the key role to ensure the effective and comprehensive prevention and engineering control works for preventing the mining slags at the lower stream from failure and initiation.
The Hou gully in Shimian County is a typical debris-flow gully where either natural debris flow or mine debris flow can occur. This paper is based on the investigation and analysis on the deposition characteristics of former natural debris flows in history, mine debris flows since exploitation of mineral resource in recent years and the combined debris flow occurred on July 4, 2013. The combined effect of natural debris flow and mine debris flow is summarized in the following five aspects：(1)the multi effect of the solid materials supplying for debris flow,(2)the reversal effects of debris flow development and evolution,(3)the complex effect in debris flow initiation and occurrence process,(4)the amplification effect in debris flow downstream transporting process and (5)the chain effect during debris flow damaging process. In addition, prevention countermeasures are put forward for the Hou gully debris flow at the end of this paper. It is suggested that the control works built at the middle stream for the blocking of natural debris flow can play the key role to ensure the effective and comprehensive prevention and engineering control works for preventing the mining slags at the lower stream from failure and initiation.
2014, 22(5): 936-943.
For its high and steep terrain, complex geology, sensitive environments and construction difficulties, K227 landslide of Shuangyong highway became a typical complex cutting ultrahigh slope and the focus of concern during constructing and maintaining. Based on practice, thinking, evaluation and monitoring in the long-term governance process of participation, through the analysis of terrain conditions, geological conditions, environmental conditions, stress adjustment and deformation control, the safety evaluation indexes system of the slope was built. The weight of each index was calculated by analytic hierarchy process. With fuzzy comprehensive evaluation method, expert authority factor correction and maximum subordination degree principle, the comprehensive model for slope safety evaluation was established. Meanwhile, the calculation of limit equilibrium method and finite element analysis, and monitoring records in site had confirmed the safety evaluation result. Therefore, it was proved to be an effective method for evaluating treatment effect of complex cutting high slope disease.
For its high and steep terrain, complex geology, sensitive environments and construction difficulties, K227 landslide of Shuangyong highway became a typical complex cutting ultrahigh slope and the focus of concern during constructing and maintaining. Based on practice, thinking, evaluation and monitoring in the long-term governance process of participation, through the analysis of terrain conditions, geological conditions, environmental conditions, stress adjustment and deformation control, the safety evaluation indexes system of the slope was built. The weight of each index was calculated by analytic hierarchy process. With fuzzy comprehensive evaluation method, expert authority factor correction and maximum subordination degree principle, the comprehensive model for slope safety evaluation was established. Meanwhile, the calculation of limit equilibrium method and finite element analysis, and monitoring records in site had confirmed the safety evaluation result. Therefore, it was proved to be an effective method for evaluating treatment effect of complex cutting high slope disease.
2014, 22(5): 944-950.
The exploration, sampling and in-situ testing at river beds are one of the most common technical problems associated with hydropower projects in China. The Jinsha River Wudongde Hydropower Station Dam Area has the problems of the riverbed overburden thickness, composition, structure, genetic diversity of hybrid uneven, high cofferdam and deep foundation pit stability. Therefore, we carried out special research work on exploration and sampling technique and in-situ test method. We obtain undisturbed samples with specially developed for single and double tube type hammer. The method makes up for the deficiency of drilling sampling and visualization technology(such as borehole digital TV,hole drilling electromagnetic wave CT) and conventional geophysical methods(such as seismic exploration, borehole acoustic test) combined with the creative development of in situ test. They are comprehensive to identify the composition and structure of river bed overburden and riverbed deep cover. They open up a new path on the layer geological investigation. The engineering properties of layer provides the premise and analysis for the geological high cofferdam and deep foundation pit stability evaluation. The treatment engineering design provides the geological basis with sufficient reliability. They can be used for reference in similar engineering geological investigation.
The exploration, sampling and in-situ testing at river beds are one of the most common technical problems associated with hydropower projects in China. The Jinsha River Wudongde Hydropower Station Dam Area has the problems of the riverbed overburden thickness, composition, structure, genetic diversity of hybrid uneven, high cofferdam and deep foundation pit stability. Therefore, we carried out special research work on exploration and sampling technique and in-situ test method. We obtain undisturbed samples with specially developed for single and double tube type hammer. The method makes up for the deficiency of drilling sampling and visualization technology(such as borehole digital TV,hole drilling electromagnetic wave CT) and conventional geophysical methods(such as seismic exploration, borehole acoustic test) combined with the creative development of in situ test. They are comprehensive to identify the composition and structure of river bed overburden and riverbed deep cover. They open up a new path on the layer geological investigation. The engineering properties of layer provides the premise and analysis for the geological high cofferdam and deep foundation pit stability evaluation. The treatment engineering design provides the geological basis with sufficient reliability. They can be used for reference in similar engineering geological investigation.
2014, 22(5): 951-957.
The Weihe Basin can be one of the most developed areas associated with ground fissures and geo-hazards in China and even in the world. This paper considers the ground fissure disasters on the influence of site condition, especially to the site soil of the dynamic characteristics and dynamic response. Under the condition of constant pressure consolidation, the consolidated undrained dynamic triaxial tests are carried out on the loess at the Xi'an area ground fissures belt with different confining pressures. The tests result in dynamical parameters. Based on the experimental results, the change laws of dynamic shear modulus with strain relationship and damping ratio with strain relationship are analyzed. And the equivalent visco-elastic constitutive model is established, which lays the foundation for the further analysis of dynamic response of soil field.
The Weihe Basin can be one of the most developed areas associated with ground fissures and geo-hazards in China and even in the world. This paper considers the ground fissure disasters on the influence of site condition, especially to the site soil of the dynamic characteristics and dynamic response. Under the condition of constant pressure consolidation, the consolidated undrained dynamic triaxial tests are carried out on the loess at the Xi'an area ground fissures belt with different confining pressures. The tests result in dynamical parameters. Based on the experimental results, the change laws of dynamic shear modulus with strain relationship and damping ratio with strain relationship are analyzed. And the equivalent visco-elastic constitutive model is established, which lays the foundation for the further analysis of dynamic response of soil field.
2014, 22(5): 958-964.
Backfill mining could induce noticeable ground movement when it is applied to be mining of large-scale metal orebody. The paper aims to grasp the deformation mechanism of the surface movement and destruction in Jinchuan Nickel Mine Area caused by underground mining. It uses the GPS monitoring system that is built covering the whole area. The range and the characteristics of the surface movement area are quantified using the data from the site investigation and monitoring. The condition and law that are related to the rock mass movement and deformation are analyzed. Besides, a number of predictive points of view are made. Consequently, this paper can be used as a reference for technicians and researchers when facing the mines that have a similar engineering and rock mechanics conditions as this mine area.
Backfill mining could induce noticeable ground movement when it is applied to be mining of large-scale metal orebody. The paper aims to grasp the deformation mechanism of the surface movement and destruction in Jinchuan Nickel Mine Area caused by underground mining. It uses the GPS monitoring system that is built covering the whole area. The range and the characteristics of the surface movement area are quantified using the data from the site investigation and monitoring. The condition and law that are related to the rock mass movement and deformation are analyzed. Besides, a number of predictive points of view are made. Consequently, this paper can be used as a reference for technicians and researchers when facing the mines that have a similar engineering and rock mechanics conditions as this mine area.
2014, 22(5): 965-974.
The fragile geological environment and fulsome engineering activities can cause frequent geological disasters in Shanxi(referred to as the 3F problem chain). The fragile geological environment has many performances, including：gully topography in the East Loess Plateau, mountainous topography pattern inLvliang(Mountain) Taihang(Mountain) sandwiched five basins,the Fen River passes through the middle of Shanxi, active new tectonic activities, distribution of loess, red clay, soft soil, saline soil and other special soil, sparse vegetation and serious soil erosion. The excessive human engineering activities including the construction of towns in mountain areas, engineering exploration and mining activities have the characteristics of high density and strength, which has a strong influence on the geological environment. The induced various engineering or mining geological disasters have associated with the characteristics in a chain or a family. The diversification rend of geological environment damage is obvious. Based on the analysis of 3F chain issues, this paper discusses on the oretical issues, the whole idea need to be solved and the scientific solution for such problems with systematic concept and global outlook. A profound understanding and in-depth study of 3F chain is also the fundamental way to solve the problems of geological disasters and geological environmental issues in Shanxi.
The fragile geological environment and fulsome engineering activities can cause frequent geological disasters in Shanxi(referred to as the 3F problem chain). The fragile geological environment has many performances, including：gully topography in the East Loess Plateau, mountainous topography pattern inLvliang(Mountain) Taihang(Mountain) sandwiched five basins,the Fen River passes through the middle of Shanxi, active new tectonic activities, distribution of loess, red clay, soft soil, saline soil and other special soil, sparse vegetation and serious soil erosion. The excessive human engineering activities including the construction of towns in mountain areas, engineering exploration and mining activities have the characteristics of high density and strength, which has a strong influence on the geological environment. The induced various engineering or mining geological disasters have associated with the characteristics in a chain or a family. The diversification rend of geological environment damage is obvious. Based on the analysis of 3F chain issues, this paper discusses on the oretical issues, the whole idea need to be solved and the scientific solution for such problems with systematic concept and global outlook. A profound understanding and in-depth study of 3F chain is also the fundamental way to solve the problems of geological disasters and geological environmental issues in Shanxi.
2014, 22(5): 975-980.
The section from Meihuashan to Tianshengqiao in Liupanshui-Zhanyi Double-track railway passes through the main cordillera of Meihuashan Mountain. In this area, the landform is obstructive; geological conditions are very intricate; geologic structure, unfavorable geology and special rock and soil are developed, which bring great difficulty for route selection, design and construction of the railway. Comprehensive geological survey methods and means are adopted to find out the regional geological characteristics and the engineering geological conditions of every route scheme, which provide credible basic geological information for route selection. The linchpin geological factors for route selection are the groups of landslides, talus, perilous and falling rocks along Guanyin-River and Shushe-Valley, the disserve of karst-water and karst in long and deep tunnel and the old coal mining area. Through the comparison of the engineering geological conditions, construction quantity and invest of long-tunnel scheme, short-tunnel scheme and outcropping in Guanyin-River scheme of the railway from Meihuashan to Tianshengqiao, the outcropping in Guanyin-River scheme is commended, which is No.1 and No.2 Wumengshan Tunnel passing through the main cordillera of Meihuashan Mountain. The geological conditions are better, construction security is higher, and the aftereffect of construction and operation is very good. This paper offers reference for geologic route selection in the rugged and precipitous mountains of complicated geological conditions.
The section from Meihuashan to Tianshengqiao in Liupanshui-Zhanyi Double-track railway passes through the main cordillera of Meihuashan Mountain. In this area, the landform is obstructive; geological conditions are very intricate; geologic structure, unfavorable geology and special rock and soil are developed, which bring great difficulty for route selection, design and construction of the railway. Comprehensive geological survey methods and means are adopted to find out the regional geological characteristics and the engineering geological conditions of every route scheme, which provide credible basic geological information for route selection. The linchpin geological factors for route selection are the groups of landslides, talus, perilous and falling rocks along Guanyin-River and Shushe-Valley, the disserve of karst-water and karst in long and deep tunnel and the old coal mining area. Through the comparison of the engineering geological conditions, construction quantity and invest of long-tunnel scheme, short-tunnel scheme and outcropping in Guanyin-River scheme of the railway from Meihuashan to Tianshengqiao, the outcropping in Guanyin-River scheme is commended, which is No.1 and No.2 Wumengshan Tunnel passing through the main cordillera of Meihuashan Mountain. The geological conditions are better, construction security is higher, and the aftereffect of construction and operation is very good. This paper offers reference for geologic route selection in the rugged and precipitous mountains of complicated geological conditions.
2014, 22(5): 981-988.
As the symbols of Jinan city, the springs are essentially valuable for the citys economy and society. It is important to follow the influence of sudden sewage leakage. This paper conceptualizes the concept model of hydrogeology. It studies the temporal and spatial distribution of groundwater and the features of contaminant transportation using the building transient groundwater flow model. On this basis, the effect of a new built project to the groundwater environment is researched. The features of the contaminant transportation are investigated by setting different longitudinal and transverse dispersities. The result shows that the advection plays a leading role in the longitudinal transportation of contaminants in the area near the spring groups. But it is exactly the opposite in the transverse direction. The research result has the model significance to the groundwater environment conservation and the groundwater pollution control.
As the symbols of Jinan city, the springs are essentially valuable for the citys economy and society. It is important to follow the influence of sudden sewage leakage. This paper conceptualizes the concept model of hydrogeology. It studies the temporal and spatial distribution of groundwater and the features of contaminant transportation using the building transient groundwater flow model. On this basis, the effect of a new built project to the groundwater environment is researched. The features of the contaminant transportation are investigated by setting different longitudinal and transverse dispersities. The result shows that the advection plays a leading role in the longitudinal transportation of contaminants in the area near the spring groups. But it is exactly the opposite in the transverse direction. The research result has the model significance to the groundwater environment conservation and the groundwater pollution control.
2014, 22(5): 989-996.
This paper analyzes the work content, work flow, and the data treatment scheme of engineering geology. We think that engineering geological data is a kind of typical Big Data,which can improve the ordering and sharing of these data through geological semantics and database technology. Through the geological syntax, patterns, CAD technology and 3d visualization technology, improve the efficiency and standardization of 2d geological drawing and the visual insight of geological structure. Through the multisensor data fusion and mining technology, improve the depth and breadth of geological monitoring application. Through the network technology, improve work efficiency and convenience of data sharing. Through the Double C pattern, integrate engineering geological data and various analysis. Thus the traditional engineering geological data flow can be remolded from data collection to data archiving, and achieve the goal of informatization and digitization.
This paper analyzes the work content, work flow, and the data treatment scheme of engineering geology. We think that engineering geological data is a kind of typical Big Data,which can improve the ordering and sharing of these data through geological semantics and database technology. Through the geological syntax, patterns, CAD technology and 3d visualization technology, improve the efficiency and standardization of 2d geological drawing and the visual insight of geological structure. Through the multisensor data fusion and mining technology, improve the depth and breadth of geological monitoring application. Through the network technology, improve work efficiency and convenience of data sharing. Through the Double C pattern, integrate engineering geological data and various analysis. Thus the traditional engineering geological data flow can be remolded from data collection to data archiving, and achieve the goal of informatization and digitization.
2014, 22(5): 997-1002.
The deposit in Shenhu area is a kind of complicated marine hydrate system. Thus the mechanism of its dynamic accumulation still needs to be further studied and clarified. A flow-transport-reaction model, coupled with the kinetic characteristic of hydrate reaction, has been established to evaluate the formation of the hydrate deposits. Two types of the marine hydrate systems, one formed by only dissolved methane and the other formed by both dissolved methane and free gas, have been respectively discussed about how they contribute to the accumulation of the hydrate-bearing sediments. The hydrate saturation at the bottom of hydrate stable zone has been deduced, and the influences of the free gas content and the hydrate kinetic characteristics have also been studied to examine the collection process of hydrate deposits in this area. The results imply that certain kinds of special geologic events have happened to transform the formation and aggregation of the hydrate deposits in this area.
The deposit in Shenhu area is a kind of complicated marine hydrate system. Thus the mechanism of its dynamic accumulation still needs to be further studied and clarified. A flow-transport-reaction model, coupled with the kinetic characteristic of hydrate reaction, has been established to evaluate the formation of the hydrate deposits. Two types of the marine hydrate systems, one formed by only dissolved methane and the other formed by both dissolved methane and free gas, have been respectively discussed about how they contribute to the accumulation of the hydrate-bearing sediments. The hydrate saturation at the bottom of hydrate stable zone has been deduced, and the influences of the free gas content and the hydrate kinetic characteristics have also been studied to examine the collection process of hydrate deposits in this area. The results imply that certain kinds of special geologic events have happened to transform the formation and aggregation of the hydrate deposits in this area.
2014, 22(5): 1003-1007.
The coal resources in semiarid-arid northwestern China are charactered with rich reserves, shallow buried, but short water source. The water fracture zone of overburden rock due to coal mining could develop to the surface, destroying the shallow water resources, causing the loss of phreatic water, drying up the surface water, and deteriorating the ecological and geological environment. Therefore, the implementation of water resources protective exploitation(water preserved mining) is the only choice for the coal mining in northwestern China. This paper discussed the history and status of water preserved mining,analyzed the basic condition and mechanism of goaf water storage, yielded the predicting approach for the amount of goaf water, showed the quantity and quality of goaf water with an example, and suggested that the goaf water storage is the most effective way for the shallow buried coal mining in the northwestern arid areas of China.
The coal resources in semiarid-arid northwestern China are charactered with rich reserves, shallow buried, but short water source. The water fracture zone of overburden rock due to coal mining could develop to the surface, destroying the shallow water resources, causing the loss of phreatic water, drying up the surface water, and deteriorating the ecological and geological environment. Therefore, the implementation of water resources protective exploitation(water preserved mining) is the only choice for the coal mining in northwestern China. This paper discussed the history and status of water preserved mining,analyzed the basic condition and mechanism of goaf water storage, yielded the predicting approach for the amount of goaf water, showed the quantity and quality of goaf water with an example, and suggested that the goaf water storage is the most effective way for the shallow buried coal mining in the northwestern arid areas of China.
2014, 22(5): 1008-1014.
It is well-acknowledged that the tectonic coal is necessary for the occurrence of a coal and gas outburst. Therefore, a good classification of the tectonic coal is significant to the prediction and precaution of the outburst. It firstly gives a new definition about tectonic coal according to the mechanical properties appeared by the tectonic coal during the outburst, which is a two-phase material combined by gas and coal, and characterized by low strength and different gas content from the origin coal. With these characters, three types tectonic coal are classified as 01 gas tectonic coal(01 GTC), 01 strength tectonic coal(01 STC) and 02 tectonic coal(02 TC),respectively correspond to coal with high gas content only, low strength only and both. Secondly, six types of genesis property tectonic coal are classified when combined the mechanical property classification and the brittle and ductile of rock failure, which is the traditional geology classification of rock failure form. It embodied three brittleness tectonic coals and three ductile tectonic coals, named as 01 brittle GTC(01 BGTC), 02 GTC,et al. Thirdly, it investigates the mechanism of the attendance in outburst by different tectonic coal. The stress concentration around STC,gas pore pressures and absorption weaken the effect on the coal. The high gas pressure to destroy and throw the coal are distinctive. Finally, based on the genesis property classification, it carries out a thorough investigation about the influence on the TC distribution and its gas genesis and storage condition by geology factors.
It is well-acknowledged that the tectonic coal is necessary for the occurrence of a coal and gas outburst. Therefore, a good classification of the tectonic coal is significant to the prediction and precaution of the outburst. It firstly gives a new definition about tectonic coal according to the mechanical properties appeared by the tectonic coal during the outburst, which is a two-phase material combined by gas and coal, and characterized by low strength and different gas content from the origin coal. With these characters, three types tectonic coal are classified as 01 gas tectonic coal(01 GTC), 01 strength tectonic coal(01 STC) and 02 tectonic coal(02 TC),respectively correspond to coal with high gas content only, low strength only and both. Secondly, six types of genesis property tectonic coal are classified when combined the mechanical property classification and the brittle and ductile of rock failure, which is the traditional geology classification of rock failure form. It embodied three brittleness tectonic coals and three ductile tectonic coals, named as 01 brittle GTC(01 BGTC), 02 GTC,et al. Thirdly, it investigates the mechanism of the attendance in outburst by different tectonic coal. The stress concentration around STC,gas pore pressures and absorption weaken the effect on the coal. The high gas pressure to destroy and throw the coal are distinctive. Finally, based on the genesis property classification, it carries out a thorough investigation about the influence on the TC distribution and its gas genesis and storage condition by geology factors.
2014, 22(5): 1015-1021.
In recent years, high-density electrical method have been used more and more widely and the researches on resolution influence factors analysis of the high-density electrical method have been drawn much attentions. This paper takes the partially erect anomaly of a uniform half-space as detect target, building different models to simulate and analyze with the Wenner high-density electrical device, employing 2DRES software to process forward and inverse numerical simulation and analysis to obtain the effects of the terrain, resistivity differences, depth to diameter ratio and deepening on the high-density electrical probe resolution. The results show that the undulating terrain makes the apparent resistivity anomaly location displaced, shape distorted and the resolution reduced; the detecting resolution of high-density resistivity method increases with the increase of resistivity difference; the detecting resolution decreases with the increase of depth to diameter ratio, and the detecting resolution increases with the increase of extended depth when the lateral width of certain anomalies reaching a critical level. Finally, the recommendations to improve the detecting resolution are given by combining the theoretical analysis and the engineering application.
In recent years, high-density electrical method have been used more and more widely and the researches on resolution influence factors analysis of the high-density electrical method have been drawn much attentions. This paper takes the partially erect anomaly of a uniform half-space as detect target, building different models to simulate and analyze with the Wenner high-density electrical device, employing 2DRES software to process forward and inverse numerical simulation and analysis to obtain the effects of the terrain, resistivity differences, depth to diameter ratio and deepening on the high-density electrical probe resolution. The results show that the undulating terrain makes the apparent resistivity anomaly location displaced, shape distorted and the resolution reduced; the detecting resolution of high-density resistivity method increases with the increase of resistivity difference; the detecting resolution decreases with the increase of depth to diameter ratio, and the detecting resolution increases with the increase of extended depth when the lateral width of certain anomalies reaching a critical level. Finally, the recommendations to improve the detecting resolution are given by combining the theoretical analysis and the engineering application.
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