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Editor Work2016 Vol. 24, No. 3
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2016, 24(3): 339-344.
Abstract
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This paper applies the cloud model theory to engineering geology classification of the surrounding rock mass of tunnel. It calculates the cloud model membership degrees via instituting multi-level quantitative system and assessment level standards of the surrounding rock mass. It then determines the engineering geology classification of the surrounding rock mass by combining qualitative assessment with quantitative classifying results. Through engineering practices, it is shown that the cloud model theory unifies the ambiguity and randomness associated with the conventional surrounding rock mass classification. Its results are compared with the results that are jointly determined by several geological engineers. This comparison shows that the results of rock mass classification are identical in 14 sections among the total 15 sections. The new method has high accuracy and can be reasonably practicable for the classification of the surrounding rock mass of tunnel.
This paper applies the cloud model theory to engineering geology classification of the surrounding rock mass of tunnel. It calculates the cloud model membership degrees via instituting multi-level quantitative system and assessment level standards of the surrounding rock mass. It then determines the engineering geology classification of the surrounding rock mass by combining qualitative assessment with quantitative classifying results. Through engineering practices, it is shown that the cloud model theory unifies the ambiguity and randomness associated with the conventional surrounding rock mass classification. Its results are compared with the results that are jointly determined by several geological engineers. This comparison shows that the results of rock mass classification are identical in 14 sections among the total 15 sections. The new method has high accuracy and can be reasonably practicable for the classification of the surrounding rock mass of tunnel.
2016, 24(3): 345-351.
The safety operation of underground railway is seriously affected by water corrosion. The key to solve the problem is correctly evaluating the corrosion of groundwater. Taking Shenzhen Metro Line 11as an example, erosion analysis reports of 627 groundwater samples taken from 30 sections of Metro Line 11 are collected. The whole line of groundwater corrosion intensity distribution is obtained, which is analyzed combined with the seawater intrusion area that passed through by Shenzhen Metro Line 11. The conclusion is the following. For the typical environment of seawater intrusion, there is a closely relationship between the groundwater erosion and the distribution of seawater intrusion, which includes the reclamation area. Discrimination of steel corrosion grade of subway underground structure should be carried out according to the environment of wet and dry cycles. The study provides guidance for the groundwater corrosion evaluation of subway lines in the coastal city with seawater intrusion area.
The safety operation of underground railway is seriously affected by water corrosion. The key to solve the problem is correctly evaluating the corrosion of groundwater. Taking Shenzhen Metro Line 11as an example, erosion analysis reports of 627 groundwater samples taken from 30 sections of Metro Line 11 are collected. The whole line of groundwater corrosion intensity distribution is obtained, which is analyzed combined with the seawater intrusion area that passed through by Shenzhen Metro Line 11. The conclusion is the following. For the typical environment of seawater intrusion, there is a closely relationship between the groundwater erosion and the distribution of seawater intrusion, which includes the reclamation area. Discrimination of steel corrosion grade of subway underground structure should be carried out according to the environment of wet and dry cycles. The study provides guidance for the groundwater corrosion evaluation of subway lines in the coastal city with seawater intrusion area.
2016, 24(3): 352-362.
The movement and transformation of laterite contaminated by phosphorus are investigated in this paper. Soil column migration tests are carried out on Yunnan laterite with sodium hexametaphosphate associated with the influence of the depth of soil column tests. It shows that the relative quality and clay content decrease as the depth increase. The liquid limit, plastic limit and plasticity index decrease as the depth increase, their minimum values appear in the boundaries moisture content. The beta sodium tecto-dioxoferrate is generated, its maximum value appears in the phosphorus content. The ferrous oxide content has seriously changed on the surface of soil column. The microstructure images show that the structural unit of laterite contaminated by phosphorus have changed from compactly squamose structure to honeycomb structure and then to incompactly bee coagulation structure. The maximum value appears in the void ratio of the microstructure images. The iron and aluminum ion concentration of soaking solution on the surface of soil column gradually increase as time gone. Few iron and aluminum ion are found in seepage solution. The mechanism towards laterite contaminated by phosphorus could be accounted for hydrolyzation, adsorption-complexation, reduction-oxidation and salification. The changes of transportation and transformation characteristics of laterite contaminated by phosphorus may be the result of those comprehensive actions.
The movement and transformation of laterite contaminated by phosphorus are investigated in this paper. Soil column migration tests are carried out on Yunnan laterite with sodium hexametaphosphate associated with the influence of the depth of soil column tests. It shows that the relative quality and clay content decrease as the depth increase. The liquid limit, plastic limit and plasticity index decrease as the depth increase, their minimum values appear in the boundaries moisture content. The beta sodium tecto-dioxoferrate is generated, its maximum value appears in the phosphorus content. The ferrous oxide content has seriously changed on the surface of soil column. The microstructure images show that the structural unit of laterite contaminated by phosphorus have changed from compactly squamose structure to honeycomb structure and then to incompactly bee coagulation structure. The maximum value appears in the void ratio of the microstructure images. The iron and aluminum ion concentration of soaking solution on the surface of soil column gradually increase as time gone. Few iron and aluminum ion are found in seepage solution. The mechanism towards laterite contaminated by phosphorus could be accounted for hydrolyzation, adsorption-complexation, reduction-oxidation and salification. The changes of transportation and transformation characteristics of laterite contaminated by phosphorus may be the result of those comprehensive actions.
2016, 24(3): 363-368.
The crack propagation and strength of fissured rocks under applying loads are significant for the study of rock deformation mechanism. Mortar fractured specimens have been simulated as fissured rock in the uniaxial compression experiment. Different crack length, the initial propagation angle of specimens and initial crack strength have been obtained by setting 9 experimental conditions. They have 3angles of 45, 60 and 75 and 3 crack length of 45mm, 60mm and 75mm. The compression failure mechanism is also analyzed. The results show the following. When the crack length is the same, the initial crack strength is increased by the increase of angles. When the angle is increased from 60to 75,the initial crack strength is increased faster. When the crack angle stays at a certain level, the initial crack strength is decreased by the increase of the crack length. By employing the theory of maximum circumferential stress, the failure mechanism of fractured specimens under compression is interpreted. Theoretical expression of crack propagation angle is acquired. By comparison, it is found that the measured and theoretical values of crack propagation angle are in good agreement.
The crack propagation and strength of fissured rocks under applying loads are significant for the study of rock deformation mechanism. Mortar fractured specimens have been simulated as fissured rock in the uniaxial compression experiment. Different crack length, the initial propagation angle of specimens and initial crack strength have been obtained by setting 9 experimental conditions. They have 3angles of 45, 60 and 75 and 3 crack length of 45mm, 60mm and 75mm. The compression failure mechanism is also analyzed. The results show the following. When the crack length is the same, the initial crack strength is increased by the increase of angles. When the angle is increased from 60to 75,the initial crack strength is increased faster. When the crack angle stays at a certain level, the initial crack strength is decreased by the increase of the crack length. By employing the theory of maximum circumferential stress, the failure mechanism of fractured specimens under compression is interpreted. Theoretical expression of crack propagation angle is acquired. By comparison, it is found that the measured and theoretical values of crack propagation angle are in good agreement.
2016, 24(3): 369-375.
The ordinary cement slurry has long setting time, low early strength, and poor groutability. It is difficult to guarantee quality in the complex rock grouting. It proposes the ordinary cement slurry as the base mud slurry, and it put admixture in the ordinary cement slurry admixture to adjust the cement hydration and hardening process, which forms the SJP grouting material of variable viscosity in time. The slurry has good initial liquidity and initial low viscosity. The viscosity of the slurry can increase rapidly after the pump time, the size of the pump can be maintained in good time, the slurry setting time can be controlled to the initial setting time. The pump can pump over short time interval, which can reduce slurry erosion. The slurry consolidation has fast growth of early strength and high strength characteristics late. It changes the amount of an admixture, which can be formed with the formation of adaptable grouting material depending on the characteristics of rock formation. The application results show that for steep, wide joints and broken rock grouting, the grouting material variability has good suitability of SJP viscosity. The SJP viscosity can be used as anchor grouting material. It reduces the amount of material at the same time and can save cost and working hours. The perfusion quality meets the design requirements. Meanwhile the SJP grouting material also can be used in dam reinforcement, building foundation treatment, and geological disaster control engineering applications.
The ordinary cement slurry has long setting time, low early strength, and poor groutability. It is difficult to guarantee quality in the complex rock grouting. It proposes the ordinary cement slurry as the base mud slurry, and it put admixture in the ordinary cement slurry admixture to adjust the cement hydration and hardening process, which forms the SJP grouting material of variable viscosity in time. The slurry has good initial liquidity and initial low viscosity. The viscosity of the slurry can increase rapidly after the pump time, the size of the pump can be maintained in good time, the slurry setting time can be controlled to the initial setting time. The pump can pump over short time interval, which can reduce slurry erosion. The slurry consolidation has fast growth of early strength and high strength characteristics late. It changes the amount of an admixture, which can be formed with the formation of adaptable grouting material depending on the characteristics of rock formation. The application results show that for steep, wide joints and broken rock grouting, the grouting material variability has good suitability of SJP viscosity. The SJP viscosity can be used as anchor grouting material. It reduces the amount of material at the same time and can save cost and working hours. The perfusion quality meets the design requirements. Meanwhile the SJP grouting material also can be used in dam reinforcement, building foundation treatment, and geological disaster control engineering applications.
2016, 24(3): 376-383.
The distribution of coal gangue particle size along the vertical profile shows obvious regularity after been abandoned. Based on field gradation, the indoor direct shear tests of three grading weathering gangues in different moisture content were completed, the test results indicate that the stress-strain relationship of weathering gangue samples is from the strain softening to the strain hardening gradually with the increase of moisture content. The effect of gradation to shear strength of weathering gangue is difference in different moisture content, the backbone formed by coarse particles has an prominent influence to the internal friction angle of weathering gangue in low sample moisture content, but with the increase of moisture content, the effect of fine particle state is even more prominent. Along with the increase of moisture content, the cohesive force values among three grading coal gangues are close to accordance, but the declining rate of internal friction angle is obvious different, when the moisture content reaches saturation, the values of internal friction angle has dropped to near zero, at this time the shear strength of weathering gangue is mainly composition by its internal cohesive force.
The distribution of coal gangue particle size along the vertical profile shows obvious regularity after been abandoned. Based on field gradation, the indoor direct shear tests of three grading weathering gangues in different moisture content were completed, the test results indicate that the stress-strain relationship of weathering gangue samples is from the strain softening to the strain hardening gradually with the increase of moisture content. The effect of gradation to shear strength of weathering gangue is difference in different moisture content, the backbone formed by coarse particles has an prominent influence to the internal friction angle of weathering gangue in low sample moisture content, but with the increase of moisture content, the effect of fine particle state is even more prominent. Along with the increase of moisture content, the cohesive force values among three grading coal gangues are close to accordance, but the declining rate of internal friction angle is obvious different, when the moisture content reaches saturation, the values of internal friction angle has dropped to near zero, at this time the shear strength of weathering gangue is mainly composition by its internal cohesive force.
2016, 24(3): 384-390.
As ecological balance and environmental protection have been increasingly recognized and valued, many developed countries have paid attentions to the ecological restoration and protection technology of slope engineering. Such technology has become the preferred solution for disaster prevention and erosion control and represented the development direction of slope protection. The shear strength of pure soil and the roots-soil composite system of two vegetation species are tested in laboratory. The two species are Astragalus adsurgens Pall. and Caragana microphylla Lam. and are planted in slope composing silty clays with low liquid limit. They are endurable to drought and barren resistance. This paper investigates the effects of different root density and moisture content on shear strength. The results show that the shear strength of the root-soil composite system increases linearly with increasing vertical pressure. Root can increase soil shear strength. The root of Astragalus adsurgens Pall. has the most noticeable effect, which is followed by Caragana microphylla Lam.As the root density increases, the shear strength increases. But, the shear strength of root soil-composite increases firstly and then decreases as the moisture increases. Plant root has little effect on the internal friction angle, while it has larger effect on the cohesion. So the increase of cohesion can greatly improve root-soil composite shear strength. The results of this test have great significance to the ecological protection technology of the slope composing silty clays with low liquid limit and ecological management of mining area in the way of plant selection and configuration.
As ecological balance and environmental protection have been increasingly recognized and valued, many developed countries have paid attentions to the ecological restoration and protection technology of slope engineering. Such technology has become the preferred solution for disaster prevention and erosion control and represented the development direction of slope protection. The shear strength of pure soil and the roots-soil composite system of two vegetation species are tested in laboratory. The two species are Astragalus adsurgens Pall. and Caragana microphylla Lam. and are planted in slope composing silty clays with low liquid limit. They are endurable to drought and barren resistance. This paper investigates the effects of different root density and moisture content on shear strength. The results show that the shear strength of the root-soil composite system increases linearly with increasing vertical pressure. Root can increase soil shear strength. The root of Astragalus adsurgens Pall. has the most noticeable effect, which is followed by Caragana microphylla Lam.As the root density increases, the shear strength increases. But, the shear strength of root soil-composite increases firstly and then decreases as the moisture increases. Plant root has little effect on the internal friction angle, while it has larger effect on the cohesion. So the increase of cohesion can greatly improve root-soil composite shear strength. The results of this test have great significance to the ecological protection technology of the slope composing silty clays with low liquid limit and ecological management of mining area in the way of plant selection and configuration.
2016, 24(3): 391-397.
In this paper, a new type of geogrid structure named steel-plastic composite tenon geogrid is designed by attaching tenon to steel-plastic geogrid. Laboratory direct shear tests and pull-out tests between various typical backfills and geogrid and tenon geogrid are carried out respectively. The test results demonstrate that the tenon is useful to improve the mechanical characteristics between geogrid and backfills. Damage model between tenon geogrid and soils is analyzed. A simple theoretical formula describing the interaction shear strength is deduced. Comparisons between laboratory test results and theoretical results indicate that the friction angle based on the formula calculations coincides with that of the test results, although the cohesion is far different from the that of the test results. Based on the test results, the value of tenons contribution to cohesion is recommended to be 2 kPa to 7 kPa.
In this paper, a new type of geogrid structure named steel-plastic composite tenon geogrid is designed by attaching tenon to steel-plastic geogrid. Laboratory direct shear tests and pull-out tests between various typical backfills and geogrid and tenon geogrid are carried out respectively. The test results demonstrate that the tenon is useful to improve the mechanical characteristics between geogrid and backfills. Damage model between tenon geogrid and soils is analyzed. A simple theoretical formula describing the interaction shear strength is deduced. Comparisons between laboratory test results and theoretical results indicate that the friction angle based on the formula calculations coincides with that of the test results, although the cohesion is far different from the that of the test results. Based on the test results, the value of tenons contribution to cohesion is recommended to be 2 kPa to 7 kPa.
2016, 24(3): 398-408.
Arbitrary Lagrangian-Eulerian(ALE) methods couple the advantages of Lagrangian and Eulerian methods, and avoid the mesh distortion problem of Lagrangian method of general finite element. The methods can effectively analyze the penetration process of open-ended pipe piles driven by high frequency hammers. Based on ALE finite element methods, the finite element model of full penetration process of open-ended pipe piles driven by high frequency vibratory hammers is built. The paper studies in detail squeezing effect, frictional resistance and soil plugging effect during pile-sinking. The computational results show that the compacting stress mainly spreads along the horizontal direction, and the compacting stress in deep soil layers is larger than compacting stress in shallow soil layers. The horizontal compacting displacements increase with the increase of penetration depth. But the maximum compacting displacement delays penetration depth. The affecting range of squeezing effect is approximately 10 times pile diameter. So it is necessary to put great emphasis on full penetration process of pipe pile. Outside friction resistance of piles increases linearly with the increase of penetration depth. Inside friction resistance of piles increases nonlinear with the increase of penetration depth. The growth rate increases gradually with the increase of penetration depth. Soil plugs of pipes are incompletely plugged conditions. Degree of soil plugs varies from unplugged conditions to partially plugged conditions. Furthermore, the influence of soil elastic modulus, frictions, vibration frequencies and pile diameters on the compacting displacements are investigated.
Arbitrary Lagrangian-Eulerian(ALE) methods couple the advantages of Lagrangian and Eulerian methods, and avoid the mesh distortion problem of Lagrangian method of general finite element. The methods can effectively analyze the penetration process of open-ended pipe piles driven by high frequency hammers. Based on ALE finite element methods, the finite element model of full penetration process of open-ended pipe piles driven by high frequency vibratory hammers is built. The paper studies in detail squeezing effect, frictional resistance and soil plugging effect during pile-sinking. The computational results show that the compacting stress mainly spreads along the horizontal direction, and the compacting stress in deep soil layers is larger than compacting stress in shallow soil layers. The horizontal compacting displacements increase with the increase of penetration depth. But the maximum compacting displacement delays penetration depth. The affecting range of squeezing effect is approximately 10 times pile diameter. So it is necessary to put great emphasis on full penetration process of pipe pile. Outside friction resistance of piles increases linearly with the increase of penetration depth. Inside friction resistance of piles increases nonlinear with the increase of penetration depth. The growth rate increases gradually with the increase of penetration depth. Soil plugs of pipes are incompletely plugged conditions. Degree of soil plugs varies from unplugged conditions to partially plugged conditions. Furthermore, the influence of soil elastic modulus, frictions, vibration frequencies and pile diameters on the compacting displacements are investigated.
2016, 24(3): 409-417.
For the sake of improvement of the composite foundations consolidation theory, an analytical solution is obtained for consolidation of stone column-reinforced foundations taking into account the consolidation deformation of pile under progressive loading. Column consolidation and deformation are considered with the following two assumptions:(1)the quantity of water flowing through the disturbed soil zone into the column is not equal to that flowing out from the column and (2)the difference between them is equal to the volume change of the column. In addition, the linear distribution pattern of the horizontal permeability of soil in the disturbed zone is also taken into account for the disturbance effect of columns construction on the surrounding soil. To prove the correctness of the solution, a discussion is performed in the article. If the loading time tends to zero, the obtained solution can be convert to the solution in the condition of constant load. Furthermore, if the loading time and the size of stone columns tend to zero at the same time, the obtained solution can be convert to the one-dimensional solution obtained by Terzaghi. In the end, the average degree of consolidation of a composite foundation is obtained and discussed. The results show that the influence of loading process on the consolidation is obvious. The consolidation rate under the linear distribution pattern of the horizontal permeability of soil in the disturbed zone is faster than the consolidation rate in the condition of constant permeability. The consolidation rate considering deformation of pile is slower than consolidation rate using traditional assumptions. So that it is unsafe to ignore deformation of pile. Furthermore, the differences increase gradually as the loading time, the radius ratio, the stress ratios and the permeability coefficient ratios decrease.
For the sake of improvement of the composite foundations consolidation theory, an analytical solution is obtained for consolidation of stone column-reinforced foundations taking into account the consolidation deformation of pile under progressive loading. Column consolidation and deformation are considered with the following two assumptions:(1)the quantity of water flowing through the disturbed soil zone into the column is not equal to that flowing out from the column and (2)the difference between them is equal to the volume change of the column. In addition, the linear distribution pattern of the horizontal permeability of soil in the disturbed zone is also taken into account for the disturbance effect of columns construction on the surrounding soil. To prove the correctness of the solution, a discussion is performed in the article. If the loading time tends to zero, the obtained solution can be convert to the solution in the condition of constant load. Furthermore, if the loading time and the size of stone columns tend to zero at the same time, the obtained solution can be convert to the one-dimensional solution obtained by Terzaghi. In the end, the average degree of consolidation of a composite foundation is obtained and discussed. The results show that the influence of loading process on the consolidation is obvious. The consolidation rate under the linear distribution pattern of the horizontal permeability of soil in the disturbed zone is faster than the consolidation rate in the condition of constant permeability. The consolidation rate considering deformation of pile is slower than consolidation rate using traditional assumptions. So that it is unsafe to ignore deformation of pile. Furthermore, the differences increase gradually as the loading time, the radius ratio, the stress ratios and the permeability coefficient ratios decrease.
PRELIMINARY STUDY ON MECHANISM OF SURFACE WATER INFILTRATION AT HEIFANGTAI LOESS LANDSLIDES IN GANSU
2016, 24(3): 418-424.
The groundwater at the bottom of loess plays an important role on the occurrence of Heifangtai landslides. The main source of groundwater comes from irrigation water. Irrigation water can infiltrate into the loess through cracks, then seep around to the bottom of loess. A large number of cracks are confirmed in deep loess at middle and edge tableland through ground penetrating radar. According to the irrigation and trench excavation, it is found the cracks are the main infiltration channel for surface water. Surface water along the cracks can rapidly infiltrate into the deep loess. At the tableland around the steep and typical landslide, sampling and measuring moisture content are conducted. It is found that high water content only exists at seepage points of cracks. The remaining area of the increase of water content is not obvious. The distribution of water content at the bottom of loess is controlled by joints, fissures and cracks.
The groundwater at the bottom of loess plays an important role on the occurrence of Heifangtai landslides. The main source of groundwater comes from irrigation water. Irrigation water can infiltrate into the loess through cracks, then seep around to the bottom of loess. A large number of cracks are confirmed in deep loess at middle and edge tableland through ground penetrating radar. According to the irrigation and trench excavation, it is found the cracks are the main infiltration channel for surface water. Surface water along the cracks can rapidly infiltrate into the deep loess. At the tableland around the steep and typical landslide, sampling and measuring moisture content are conducted. It is found that high water content only exists at seepage points of cracks. The remaining area of the increase of water content is not obvious. The distribution of water content at the bottom of loess is controlled by joints, fissures and cracks.
2016, 24(3): 425-434.
This paper is based on detailed geological survey of the Jiweishan landslide. It analyzes the characteristics of landslide geological environment background, slide source characteristics and deposition area. It discusses the movement characteristics of three phases including the landslide instability, collision and sliding accumulation. It establishes the geological model of Jiweishan landslide. It takes the advantage of DAN-3D numerical simulation software. The landslide is simulated by choosing the FVF combination model on the motion characteristics. It finally gets the landslide accumulation, scraping area and sliding distance features. Through analysis and comparison, the simulation results are consistent with the actual situation. So this analysis method can be used for early assessment and prediction of disaster area to provide technical support for rapid and long run-out landslide.
This paper is based on detailed geological survey of the Jiweishan landslide. It analyzes the characteristics of landslide geological environment background, slide source characteristics and deposition area. It discusses the movement characteristics of three phases including the landslide instability, collision and sliding accumulation. It establishes the geological model of Jiweishan landslide. It takes the advantage of DAN-3D numerical simulation software. The landslide is simulated by choosing the FVF combination model on the motion characteristics. It finally gets the landslide accumulation, scraping area and sliding distance features. Through analysis and comparison, the simulation results are consistent with the actual situation. So this analysis method can be used for early assessment and prediction of disaster area to provide technical support for rapid and long run-out landslide.
2016, 24(3): 435-441.
The Himalayan region locates in the western border area of China. It is the highest and youngest mountain chain in the world. This region situates in the collision zone of two plates. It has complicated geological tectonics, powerful neotectonic movements, serious mountain disasters and extremely active debris flows. These disasters frequently endanger the lifeline engineering and life and possession of the local people. However, fewer exploratory efforts are made due to the high-cold, oxygen deficit and the limit of the technology. This article is based on remote sensing research and field survey data of the large-scale and giant debris flows. It reveals that 16 relative concentrated distribution areas are prensent in this region. The debris flows in the northern slope are more developed than those in the southern slope. On this basis, the development regularity is carefully analyzed. The results show that:(1)The activities of debris flows in the Himalayan region are in the active period.(2)The debris flow gully mouths in the research area are mainly distributed in two elevation sections. One is in the range of 2800~3400m and the another is in the range of 4200~4900m.(3)The gully slope of debris flows in old stage is usually little than 100,while that of debris flow in young stage is relatively larger and is usually larger than 300.Gully slope of debris flows in mature stage is between 100and 300.On the other hand, the ice-snow melting water mudflow and rain mudflow almost have the same gully slope and dynamic conditions. The findings can have significance to prevention and treatment of debris flow disasters and the judgement of debris flow activities in this area.
The Himalayan region locates in the western border area of China. It is the highest and youngest mountain chain in the world. This region situates in the collision zone of two plates. It has complicated geological tectonics, powerful neotectonic movements, serious mountain disasters and extremely active debris flows. These disasters frequently endanger the lifeline engineering and life and possession of the local people. However, fewer exploratory efforts are made due to the high-cold, oxygen deficit and the limit of the technology. This article is based on remote sensing research and field survey data of the large-scale and giant debris flows. It reveals that 16 relative concentrated distribution areas are prensent in this region. The debris flows in the northern slope are more developed than those in the southern slope. On this basis, the development regularity is carefully analyzed. The results show that:(1)The activities of debris flows in the Himalayan region are in the active period.(2)The debris flow gully mouths in the research area are mainly distributed in two elevation sections. One is in the range of 2800~3400m and the another is in the range of 4200~4900m.(3)The gully slope of debris flows in old stage is usually little than 100,while that of debris flow in young stage is relatively larger and is usually larger than 300.Gully slope of debris flows in mature stage is between 100and 300.On the other hand, the ice-snow melting water mudflow and rain mudflow almost have the same gully slope and dynamic conditions. The findings can have significance to prevention and treatment of debris flow disasters and the judgement of debris flow activities in this area.
2016, 24(3): 442-450.
This paper analyzes the mechanism of buckling failure(slipping-bending) of the bedding slope. It uses physical mechanism model, numerical simulation and theoretical analysis. It presents the forming geological and mechanical conditions, the critical failure state discrimination and early identification marks of buckling failure. It finds that the rock stratum dip angle greater than 20is a very important geological conditions for the formation of slipping-bending. The curved uplift in the leading edge of the slope is an early sign before buckling failure. The dip angle of rock slope, the single layer thickness, the critical slope length and the depth of the buckling interact each other. The larger the rock dip angle, the more prone to produce the slipping and bending, and the more the number of layer and depth of buckling. There is a change law of negative power function between the critical slope length and the rock stratum dip angle. The flexural rigidity of bending layer and the buckling depth of bedding slope are influenced by the co-bending effect produced by the interlayer bonding. The co-bending effect plays a key role on the ultimate buckling of the bedding slope. The results have an important value for early prevention and recognition of geological hazard.
This paper analyzes the mechanism of buckling failure(slipping-bending) of the bedding slope. It uses physical mechanism model, numerical simulation and theoretical analysis. It presents the forming geological and mechanical conditions, the critical failure state discrimination and early identification marks of buckling failure. It finds that the rock stratum dip angle greater than 20is a very important geological conditions for the formation of slipping-bending. The curved uplift in the leading edge of the slope is an early sign before buckling failure. The dip angle of rock slope, the single layer thickness, the critical slope length and the depth of the buckling interact each other. The larger the rock dip angle, the more prone to produce the slipping and bending, and the more the number of layer and depth of buckling. There is a change law of negative power function between the critical slope length and the rock stratum dip angle. The flexural rigidity of bending layer and the buckling depth of bedding slope are influenced by the co-bending effect produced by the interlayer bonding. The co-bending effect plays a key role on the ultimate buckling of the bedding slope. The results have an important value for early prevention and recognition of geological hazard.
2016, 24(3): 451-458.
Bentonite has the property of swelling when meeting water. It is a desirable buffer/backfill material in the deep geological disposal for high-level radioactive waste. The expansibility is one of the most important properties for bentonite as the buffer/backfill material, and is influenced by a number of factors. For study the expansibility of bentonite, Gaomiaozi(GMZ)bentonite was taken as the research object. Gaomiaozi(GMZ)bentonite had been proposed as the first choice of buffer/backfill material for the high-level radioactive waste disposal in China. Its expansibility was studied by the constant volume swelling test method which is one of the commonest methods for measuring the swelling pressure of bentonite. In these tests, water content and dry density were chosen as the control variable. Two types of dry density and three types of water content were adopted in the tests. Results of the swelling tests show that the shape of swelling curves and the maximum swelling pressure depend on the water content and dry density of the bentonite samples. There are conspicuous double-peak shapes of the swelling curve for the samples with low dry density. When the dry density is high, the swelling curves have different shapes with different water contents. The curve's shapes change from double-peak to smooth curve with the water content increasing. For analysis of the results of swelling tests, the mercury intrusion porosimetry(MIP)test has been carried out. MIP test results indicate that the pore size distribution curves of samples also depend on the water content and dry density, with the volume of inter-aggregate pores increasing as the water content or dry density decreases. In accordance with the relevant researches, the swelling curve of GMZ bentonite is deeply influenced by the volume of the inter-aggregate pores. When meeting water, the bentonite aggregates absorb water and swell quickly. When the inter-aggregate pores are large enough, there will be sufficient space for swelled aggregates to form a provisional structure. The provisional structure will collapse with the swelling pressure reach the limit load. Then the measured pressure fall and inner structure of bentonite recombination. The hydration is continuous so that the curve will get the second peak. Therefore, a double-peak structure can be observed when the space of inter-aggregate is great. With the volume of inter-aggregate pore decrease, the swell curve of bentonite changes from a double-peak structure to a smooth curve.
Bentonite has the property of swelling when meeting water. It is a desirable buffer/backfill material in the deep geological disposal for high-level radioactive waste. The expansibility is one of the most important properties for bentonite as the buffer/backfill material, and is influenced by a number of factors. For study the expansibility of bentonite, Gaomiaozi(GMZ)bentonite was taken as the research object. Gaomiaozi(GMZ)bentonite had been proposed as the first choice of buffer/backfill material for the high-level radioactive waste disposal in China. Its expansibility was studied by the constant volume swelling test method which is one of the commonest methods for measuring the swelling pressure of bentonite. In these tests, water content and dry density were chosen as the control variable. Two types of dry density and three types of water content were adopted in the tests. Results of the swelling tests show that the shape of swelling curves and the maximum swelling pressure depend on the water content and dry density of the bentonite samples. There are conspicuous double-peak shapes of the swelling curve for the samples with low dry density. When the dry density is high, the swelling curves have different shapes with different water contents. The curve's shapes change from double-peak to smooth curve with the water content increasing. For analysis of the results of swelling tests, the mercury intrusion porosimetry(MIP)test has been carried out. MIP test results indicate that the pore size distribution curves of samples also depend on the water content and dry density, with the volume of inter-aggregate pores increasing as the water content or dry density decreases. In accordance with the relevant researches, the swelling curve of GMZ bentonite is deeply influenced by the volume of the inter-aggregate pores. When meeting water, the bentonite aggregates absorb water and swell quickly. When the inter-aggregate pores are large enough, there will be sufficient space for swelled aggregates to form a provisional structure. The provisional structure will collapse with the swelling pressure reach the limit load. Then the measured pressure fall and inner structure of bentonite recombination. The hydration is continuous so that the curve will get the second peak. Therefore, a double-peak structure can be observed when the space of inter-aggregate is great. With the volume of inter-aggregate pore decrease, the swell curve of bentonite changes from a double-peak structure to a smooth curve.
2016, 24(3): 459-464.
Most of the dam foundation rock mass is granodiorite in the proposed Yalongjiang Mengdigou hydropower station, where intensive development of Hydrothermal alteration rock zone has a single width of 0.5~3m. Deformation test shows that the average deformation modulus of new micro-granodiorite is up to 31.5GPa. The deformation moduli of strong clay alteration rock and weak clay alteration rock are 6.79GPa and 11.10GPa, respectively. Therefore, the existence of intensive altered rock zone can have a significant impact on the deformation characteristics of the dam foundation rock. There are no mature methods to calculate the deformation modulus of the complex combination of rocks with deformation characteristics of significant differences. Therefore, this article is based on the rigid bearing plate deformation test and acoustic test. It uses the nonlinear regression method to analyze the correlation of rock deformation modulus and acoustics. It establishes the rock Vp-E0 correlation formula. Then, it uses the arithmetic average method to calculate the deformation modulus of typical intensive altered rock zone. The result is 18.03GPa and decreases by 42.76%to that of new micro-granodiorite rock. Meanwhile, according to a variety of altered rock band percentage, it uses the weighted average method to calculate deformation modulus of intensive altered rock zone. The result is 19.40GPa and decreases by 38.41%to that of new micro-granodiorite rock. The difference of the two methods is only 7.60%.Comparing with the rigid bearing plate result, the former is more safe and reliable. Thus, the method of nonlinear regression is suggested to calculate the deformation modulus of intensive altered rock zone at Mengdigou hydropower station.
Most of the dam foundation rock mass is granodiorite in the proposed Yalongjiang Mengdigou hydropower station, where intensive development of Hydrothermal alteration rock zone has a single width of 0.5~3m. Deformation test shows that the average deformation modulus of new micro-granodiorite is up to 31.5GPa. The deformation moduli of strong clay alteration rock and weak clay alteration rock are 6.79GPa and 11.10GPa, respectively. Therefore, the existence of intensive altered rock zone can have a significant impact on the deformation characteristics of the dam foundation rock. There are no mature methods to calculate the deformation modulus of the complex combination of rocks with deformation characteristics of significant differences. Therefore, this article is based on the rigid bearing plate deformation test and acoustic test. It uses the nonlinear regression method to analyze the correlation of rock deformation modulus and acoustics. It establishes the rock Vp-E0 correlation formula. Then, it uses the arithmetic average method to calculate the deformation modulus of typical intensive altered rock zone. The result is 18.03GPa and decreases by 42.76%to that of new micro-granodiorite rock. Meanwhile, according to a variety of altered rock band percentage, it uses the weighted average method to calculate deformation modulus of intensive altered rock zone. The result is 19.40GPa and decreases by 38.41%to that of new micro-granodiorite rock. The difference of the two methods is only 7.60%.Comparing with the rigid bearing plate result, the former is more safe and reliable. Thus, the method of nonlinear regression is suggested to calculate the deformation modulus of intensive altered rock zone at Mengdigou hydropower station.
2016, 24(3): 465-476.
The slope with colluvial soil near the entrance of tunnels has poor self-stability after excavation and is influenced by tunnel excavation. Therefore landslides can occur frequently, which can bring economic losses and endanger the safety of construction workers. This paper is based on Xiangshan tunnel and conduct three-dimensional finite element numerical simulation model on the basis of tunnel site topography and geology. It analyzes the changing processes of displacement and stress of slope near tunnel entrance and the influence of tunnel excavation to slope. Then, it optimizes the excavation scheme of tunneling. The research result shows that the abrupt change of gradient between excavation slope and original slope induces stress concentration and forms potential slip surface. Then, the tunnel excavation can impact greatly on deformation, stress and strain of front slope. Excavating slope in layers can effectively improve the stress-strain state of the slope. An appropriate shape of slope has a significant influence on stability of slope near tunnel entrance.
The slope with colluvial soil near the entrance of tunnels has poor self-stability after excavation and is influenced by tunnel excavation. Therefore landslides can occur frequently, which can bring economic losses and endanger the safety of construction workers. This paper is based on Xiangshan tunnel and conduct three-dimensional finite element numerical simulation model on the basis of tunnel site topography and geology. It analyzes the changing processes of displacement and stress of slope near tunnel entrance and the influence of tunnel excavation to slope. Then, it optimizes the excavation scheme of tunneling. The research result shows that the abrupt change of gradient between excavation slope and original slope induces stress concentration and forms potential slip surface. Then, the tunnel excavation can impact greatly on deformation, stress and strain of front slope. Excavating slope in layers can effectively improve the stress-strain state of the slope. An appropriate shape of slope has a significant influence on stability of slope near tunnel entrance.
2016, 24(3): 477-483.
On June 14, 2015, an unstable slope in Xingyang village Jiuli town Ermeishan city begun to slide after continuous rainfall. It was named as Wangshan-zhuakousi landslide. It threatened more than 52 people and their property. It also caused a direct economic loss of about 5million RMB, and an indirect economic loss of more than 30million RMB. Due to timely and effective emergency evacuation by the local government organization, the landslide had no casualties. On the basis of field investigation and simulation calculation, the conclusions are as follows:(1)the landslide is belonged to the slip-cracking type. Its stability is governed by tuff interlayers. In meanwhile, the rock mass structure of landslide was crushed by the early mining excavation and 512 Wenchuan earthquake, which made the stability of landslide in critical condition.(2)Rainfall was the direct triggering factor of landslide formation. The rainfall mainly infiltrated the rock mass and became the groundwater which flowed along the tuff layer. With its weight increasing, stability coefficient of landslide was gradually reduced until high-speed landslide happened.(3)According to the characteristics of landslide in basalt area, the corresponding landslide emergency safety measures are summarizes.
On June 14, 2015, an unstable slope in Xingyang village Jiuli town Ermeishan city begun to slide after continuous rainfall. It was named as Wangshan-zhuakousi landslide. It threatened more than 52 people and their property. It also caused a direct economic loss of about 5million RMB, and an indirect economic loss of more than 30million RMB. Due to timely and effective emergency evacuation by the local government organization, the landslide had no casualties. On the basis of field investigation and simulation calculation, the conclusions are as follows:(1)the landslide is belonged to the slip-cracking type. Its stability is governed by tuff interlayers. In meanwhile, the rock mass structure of landslide was crushed by the early mining excavation and 512 Wenchuan earthquake, which made the stability of landslide in critical condition.(2)Rainfall was the direct triggering factor of landslide formation. The rainfall mainly infiltrated the rock mass and became the groundwater which flowed along the tuff layer. With its weight increasing, stability coefficient of landslide was gradually reduced until high-speed landslide happened.(3)According to the characteristics of landslide in basalt area, the corresponding landslide emergency safety measures are summarizes.
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