2012 Vol. 34 No. 1
Abstract：
The author ' s main achievements in the basic theories of sand dynamics in the past three decades are summarized from the following five aspects:1) 2D and 3D dynamic effective strength criteria considering six frictional and non-frictional effects;2) a cyclic elasto-plastic model based on several new experimental findings of constitutive laws such as reversible and irreversible dilatancies;3) a constitutive theory of large post-liquefaction deformation with emphasis on the establishment of a cohesive theoretical framework consisting of mechanical laws, physical mechanisms, constitutive descriptions, numerical algorithms and pragmatic methods of prediction;4) a static and cyclic elasto-plastic model for interfaces between soils and structures, which are established based on five basic experimental laws;5) seismic earth pressure theory for rigid retaining walls and shallow-buried structures under any lateral displacement. These advances are obtained based on experimental observations, numerical simulations, mechanism analysis and theoretical description. Special attention in the present study is paid to the deep understanding of the realistic dynamic behaviours, rational descriptions of the cyclic effects of dynamic loadings induced by earthquakes, and new developments of simplified and pragmatic methods of prediction.
The author ' s main achievements in the basic theories of sand dynamics in the past three decades are summarized from the following five aspects:1) 2D and 3D dynamic effective strength criteria considering six frictional and non-frictional effects;2) a cyclic elasto-plastic model based on several new experimental findings of constitutive laws such as reversible and irreversible dilatancies;3) a constitutive theory of large post-liquefaction deformation with emphasis on the establishment of a cohesive theoretical framework consisting of mechanical laws, physical mechanisms, constitutive descriptions, numerical algorithms and pragmatic methods of prediction;4) a static and cyclic elasto-plastic model for interfaces between soils and structures, which are established based on five basic experimental laws;5) seismic earth pressure theory for rigid retaining walls and shallow-buried structures under any lateral displacement. These advances are obtained based on experimental observations, numerical simulations, mechanism analysis and theoretical description. Special attention in the present study is paid to the deep understanding of the realistic dynamic behaviours, rational descriptions of the cyclic effects of dynamic loadings induced by earthquakes, and new developments of simplified and pragmatic methods of prediction.
Abstract：
According to the characteristics of installation of seismic piezocone penetration testSCPTu) penetrometers and jacked-in piles, the penetration process is simulated by means of the cavity expansion theory. Based on this evaluation, the analytical solutions of the limit pressure of spherical and cylindrical cavities are presented. According to the analytical solutions and comparison of forces between SCPTu penetrometers and the piles, an analytical relationship between the data measured from SCPTu and the ultimate bearing capacity of a single pile is established. Compared with the axial load tests on a single pile in the field, the value of the new analytical solution which is used to predict the ultimate bearing capacity of jacked-in piles by utilizing the SCPTu data is verified.
According to the characteristics of installation of seismic piezocone penetration testSCPTu) penetrometers and jacked-in piles, the penetration process is simulated by means of the cavity expansion theory. Based on this evaluation, the analytical solutions of the limit pressure of spherical and cylindrical cavities are presented. According to the analytical solutions and comparison of forces between SCPTu penetrometers and the piles, an analytical relationship between the data measured from SCPTu and the ultimate bearing capacity of a single pile is established. Compared with the axial load tests on a single pile in the field, the value of the new analytical solution which is used to predict the ultimate bearing capacity of jacked-in piles by utilizing the SCPTu data is verified.
Abstract：
Talus deposit is often seen in hydropower projects in the southwest of China. Its mechanical properties are so complex that the microstructural study is often used to reveal the essence of its deformation and damage. The digital image processing technologyDIPT) is introduced to the simulation of talus deposits. Based on the study of DIPT, a Photo-To-FLAC3DPTF) auto-modeling program is developed. It is able to realize the whole process: analyzing and processing the digital images, acquiring the information and establishing the micro- model files. A new modeling method is developed for the mechanical behaviors of talus deposits. As an example, some talus deposit data of Gushui Hydropower Station are used. A micro-model for the talus deposit is established fast and correctly by means of the PTF from the field digital photo. The mechanical properties and parameters are studied by the numerical simulation of triaxial tests. The results show that the talus deposit has the feature of “bully” in deformation while that of “Unicom band” under force. A random statistical analysis method for the mechanical parameters is proposed by selecting field multiple photos. The mechanical parameters based on the statistical analysis method are very close to those of experiments in the actual engineering, indicating that the new method of acquiring mechanical parameters is credible. A new way is opened up for selecting the mechanical parameters of talus deposits, which pr ovides a useful supplement for large-scale field tests.
Talus deposit is often seen in hydropower projects in the southwest of China. Its mechanical properties are so complex that the microstructural study is often used to reveal the essence of its deformation and damage. The digital image processing technologyDIPT) is introduced to the simulation of talus deposits. Based on the study of DIPT, a Photo-To-FLAC3DPTF) auto-modeling program is developed. It is able to realize the whole process: analyzing and processing the digital images, acquiring the information and establishing the micro- model files. A new modeling method is developed for the mechanical behaviors of talus deposits. As an example, some talus deposit data of Gushui Hydropower Station are used. A micro-model for the talus deposit is established fast and correctly by means of the PTF from the field digital photo. The mechanical properties and parameters are studied by the numerical simulation of triaxial tests. The results show that the talus deposit has the feature of “bully” in deformation while that of “Unicom band” under force. A random statistical analysis method for the mechanical parameters is proposed by selecting field multiple photos. The mechanical parameters based on the statistical analysis method are very close to those of experiments in the actual engineering, indicating that the new method of acquiring mechanical parameters is credible. A new way is opened up for selecting the mechanical parameters of talus deposits, which pr ovides a useful supplement for large-scale field tests.
Abstract：
Soaking tests on self-weight collapse Q3 loess with heavy section located in Lanzhou region are conducted without water injection hole and with moisture meter and heat conduction suction probe embedded. The test results indicate that multiple collapses appear in different soil layers at different depths, and the times of the collapses decrease with the increase of loess depth. The volumetric water content at different depths has different rules: the curve above 10 m in depth is made up of 6 stages, that between 10 m and 22.5 m in depth has 5 stages, and that beneath 22.5 m in depth has 3 stages. The water above 25 m in depth infiltrates easily, and the water beneath 25 m in depth infiltrates slowly because the upper loess has collapsibility inducing the compaction and air pressure among soil pores increases gradually. The cracks far from the test pit are generated by the violent motion of the cracks near the test pit. The wetting front of the self-weight collapse loess with heavy section takes the shape of an ellipse (the major axis is horizontal), and finally the eccentricity of elliptical humidification area becomes less. The soggy angle increases with the increasing supply of water source, and its variation range is 0皛55?. The vertical infiltration velocity presents the reduction tendency of power function.
Soaking tests on self-weight collapse Q3 loess with heavy section located in Lanzhou region are conducted without water injection hole and with moisture meter and heat conduction suction probe embedded. The test results indicate that multiple collapses appear in different soil layers at different depths, and the times of the collapses decrease with the increase of loess depth. The volumetric water content at different depths has different rules: the curve above 10 m in depth is made up of 6 stages, that between 10 m and 22.5 m in depth has 5 stages, and that beneath 22.5 m in depth has 3 stages. The water above 25 m in depth infiltrates easily, and the water beneath 25 m in depth infiltrates slowly because the upper loess has collapsibility inducing the compaction and air pressure among soil pores increases gradually. The cracks far from the test pit are generated by the violent motion of the cracks near the test pit. The wetting front of the self-weight collapse loess with heavy section takes the shape of an ellipse (the major axis is horizontal), and finally the eccentricity of elliptical humidification area becomes less. The soggy angle increases with the increasing supply of water source, and its variation range is 0皛55?. The vertical infiltration velocity presents the reduction tendency of power function.
Abstract：
Model tests are carried out to study the response of capillary-barrier cover with unsaturated drainage layer under heavy rainfall situation. The test equipment includes a model box with a dimension of 2 m×1 m×1.2 m, a rainfall simulator and measuring facilities. The materials of fine layer, unsaturated drainage layer and coarse layer of the capillary-barrier cover model are silt, sand and gravel respectively, and the gradient of model is 1<>V: 3<>H. The intensity of simulated rainfall is 65~76 mm/h. During the tests the rainfall infiltration process and lateral drainage phenomenon are observed, and the surface runoff, lateral drainage and percolation through capillary-barrier cover are measured. In Test Ⅰ, runoff accounts for 69.4% of the total rainfall, and most of the infiltration is stored in the silt layer. The lateral drainage of the sand layer is significant, being 3.5% of the total rainfall; and the percolation through the cover is 2.9% of the total rainfall. In Tests Ⅱ and Ⅲ, the infiltration flux is reduced by an addition of bentonite into the silt layer. A delayed response in the lateral drainage is observed in the sand layer, and the percolation is reduced to only 0.8% of the total rainfall in Test Ⅱand no percolation is observed in Test Ⅲ. The model test results indicate that the percolation through the capillary-barrier cover can be controlled under heavy rainfall condition by reducing rainfall infiltration and enhancing capillary barrier effect and lateral drainage capacity. The research makes the application of capillary-barrier cover in humid regions feasible.
Model tests are carried out to study the response of capillary-barrier cover with unsaturated drainage layer under heavy rainfall situation. The test equipment includes a model box with a dimension of 2 m×1 m×1.2 m, a rainfall simulator and measuring facilities. The materials of fine layer, unsaturated drainage layer and coarse layer of the capillary-barrier cover model are silt, sand and gravel respectively, and the gradient of model is 1<>V: 3<>H. The intensity of simulated rainfall is 65~76 mm/h. During the tests the rainfall infiltration process and lateral drainage phenomenon are observed, and the surface runoff, lateral drainage and percolation through capillary-barrier cover are measured. In Test Ⅰ, runoff accounts for 69.4% of the total rainfall, and most of the infiltration is stored in the silt layer. The lateral drainage of the sand layer is significant, being 3.5% of the total rainfall; and the percolation through the cover is 2.9% of the total rainfall. In Tests Ⅱ and Ⅲ, the infiltration flux is reduced by an addition of bentonite into the silt layer. A delayed response in the lateral drainage is observed in the sand layer, and the percolation is reduced to only 0.8% of the total rainfall in Test Ⅱand no percolation is observed in Test Ⅲ. The model test results indicate that the percolation through the capillary-barrier cover can be controlled under heavy rainfall condition by reducing rainfall infiltration and enhancing capillary barrier effect and lateral drainage capacity. The research makes the application of capillary-barrier cover in humid regions feasible.
Abstract：
The liquefiable foundation of the subway station may bring severe seismic damages to it. Accordingly, a nonlinear model for the liquefiable foundation-subway station interaction is constituted to calculate the large liquefaction deformation by using the constitutive model for sand. The space-time transformation of the dynamic pore pressure, the displacement and the acceleration of the liquefiable foundation are analyzed. The ascent of the subway station and the dynamic settlement of the side foundation are investigated. The distributions of liquefaction area and the displacement vectors of the foundation around the subway station are analyzed. The research findings can be helpful for analyzing the earthquake damages of liquefiable foundation around the underground structures or the ground structures.
The liquefiable foundation of the subway station may bring severe seismic damages to it. Accordingly, a nonlinear model for the liquefiable foundation-subway station interaction is constituted to calculate the large liquefaction deformation by using the constitutive model for sand. The space-time transformation of the dynamic pore pressure, the displacement and the acceleration of the liquefiable foundation are analyzed. The ascent of the subway station and the dynamic settlement of the side foundation are investigated. The distributions of liquefaction area and the displacement vectors of the foundation around the subway station are analyzed. The research findings can be helpful for analyzing the earthquake damages of liquefiable foundation around the underground structures or the ground structures.
Abstract：
Based on the characteristics of the governing equations of the Biot’s consolidation, the suitable trial functions of displacement and excess pore water pressure satisfying the boundary conditions are obtained, and a semi-analytical numerical scheme for solving the plane strain consolidation of multi-layered and anisotropic soil with compressible constituents is presented by using the Galerkin’s method. Moreover, by means of the orthogonality of the trigonometric functions series, the weighted residual equations are decoupled to several independence ones associated with different series modes. A computer program is developed for solving the semi-analytical numerical equations. Several numerical examples are presented, and the numerical results are compared with other available solutions to verify the validity of the present method. The applicabilities of the present method in dealing with the anisotropy of permeability, the compressibility of pore fluid and the layered characteristics of soil are demonstrated.
Based on the characteristics of the governing equations of the Biot’s consolidation, the suitable trial functions of displacement and excess pore water pressure satisfying the boundary conditions are obtained, and a semi-analytical numerical scheme for solving the plane strain consolidation of multi-layered and anisotropic soil with compressible constituents is presented by using the Galerkin’s method. Moreover, by means of the orthogonality of the trigonometric functions series, the weighted residual equations are decoupled to several independence ones associated with different series modes. A computer program is developed for solving the semi-analytical numerical equations. Several numerical examples are presented, and the numerical results are compared with other available solutions to verify the validity of the present method. The applicabilities of the present method in dealing with the anisotropy of permeability, the compressibility of pore fluid and the layered characteristics of soil are demonstrated.
Abstract：
A coupled boundary element method for analyzing the interactive behaviour between thick raft foundation and viscoelastic half-space soil medium below the foundation in the time domain is presented. The viscoelastic rheological model for soils, combining a standard Boltzmann model in deviatoric component with an elastic model in volumetric component, is employed, and the effect of transverse shear deformation in the raft foundation is considered as it bends under varying columnn loading during construction. The boundary element method is employed to simulate the raft foundation and the ground creep respectively, and the relevant numerical formulae are derived, in which the Newton quadratic interpolation for subgrade reaction in the time interval is introduced. The present method, as well as the computing pragrom, can be used to calculate settlements and differential settlements as well as bending moments and shear forces in the raft. It is shown that the values of subgrade reaction will slightly increase on the edges of the raft and decrease in the centric domain with soil creep after the completion of construction, but the values of variation are not significant and may be ignored reasonably. Howerver, the values of the raft settlement and differential settlement and the maximum bending moments increase pronouncedly with soil creep up to a few years, and tend towards their stable values. And thus the behaviors should be paid attention to in foundation designs for some soil strata with high rheology .
A coupled boundary element method for analyzing the interactive behaviour between thick raft foundation and viscoelastic half-space soil medium below the foundation in the time domain is presented. The viscoelastic rheological model for soils, combining a standard Boltzmann model in deviatoric component with an elastic model in volumetric component, is employed, and the effect of transverse shear deformation in the raft foundation is considered as it bends under varying columnn loading during construction. The boundary element method is employed to simulate the raft foundation and the ground creep respectively, and the relevant numerical formulae are derived, in which the Newton quadratic interpolation for subgrade reaction in the time interval is introduced. The present method, as well as the computing pragrom, can be used to calculate settlements and differential settlements as well as bending moments and shear forces in the raft. It is shown that the values of subgrade reaction will slightly increase on the edges of the raft and decrease in the centric domain with soil creep after the completion of construction, but the values of variation are not significant and may be ignored reasonably. Howerver, the values of the raft settlement and differential settlement and the maximum bending moments increase pronouncedly with soil creep up to a few years, and tend towards their stable values. And thus the behaviors should be paid attention to in foundation designs for some soil strata with high rheology .
Abstract：
The seepage calculations of dams and levees with mound and layer drains on impervious strata are introduced. The slope angle of drain boundary is greater than 90 ° . The main contents and results are as follows:1) For the mound drain with the downstream water depth H2 =0, according to the Kochina ’s theory q / k = μ h 0 , the reciprocal of ratio μ between the flow quantity and the height h0 of release point is calculated, and the relevant fitting formula for 1 / μ #/is presented. By means of the transformed hypergeometric function, a formula for the exit gradient and its distributions with slope angles of 90 ° , 135 ° , 180 ° is given.2) The conformal mapping method is employed to get the critical water depth HC of the mound drain, and its derivation process is much simpler than that of the Novmurov’s method.3) For the mound drain with H2≥ HC, according to the Novmurov’s theory Δ L2= D1 H2+ D2 q/k , the proportional coefficients D1 and D2 of additional length of downstream seepage path are calculated, and two fitting formulae for D1 and D2 with enough precision are presented. The conformal mapping method is used to get the exact seepage solution in downstream district with mound drains, combined with the corresponding solution by Normurov in the upstream district of dams and levees, an example is calculated accurately to get the flow quantity ratio q / k, height of release point hs, distribution of exit gradient I, coordinates of the whole phreatic line and its inflection points to check the corresponding program of finite element and other approximate methods.4) For the mound drain with 0< H2< HC, two approximate formulae for the height hs of release point and the additional length Δ L2 of downstream seepage path are presented. The calculated results agree with the results of the finite element methods.
The seepage calculations of dams and levees with mound and layer drains on impervious strata are introduced. The slope angle of drain boundary is greater than 90 ° . The main contents and results are as follows:1) For the mound drain with the downstream water depth H2 =0, according to the Kochina ’s theory q / k = μ h 0 , the reciprocal of ratio μ between the flow quantity and the height h0 of release point is calculated, and the relevant fitting formula for 1 / μ #/is presented. By means of the transformed hypergeometric function, a formula for the exit gradient and its distributions with slope angles of 90 ° , 135 ° , 180 ° is given.2) The conformal mapping method is employed to get the critical water depth HC of the mound drain, and its derivation process is much simpler than that of the Novmurov’s method.3) For the mound drain with H2≥ HC, according to the Novmurov’s theory Δ L2= D1 H2+ D2 q/k , the proportional coefficients D1 and D2 of additional length of downstream seepage path are calculated, and two fitting formulae for D1 and D2 with enough precision are presented. The conformal mapping method is used to get the exact seepage solution in downstream district with mound drains, combined with the corresponding solution by Normurov in the upstream district of dams and levees, an example is calculated accurately to get the flow quantity ratio q / k, height of release point hs, distribution of exit gradient I, coordinates of the whole phreatic line and its inflection points to check the corresponding program of finite element and other approximate methods.4) For the mound drain with 0< H2< HC, two approximate formulae for the height hs of release point and the additional length Δ L2 of downstream seepage path are presented. The calculated results agree with the results of the finite element methods.
Abstract：
Based on the unified strength theory and a non-associated flow rule , a new analytical solution for ground reaction curve of a deep circular rock tunnel is presented taking into consideration the integrated effects of the intermediate principal stress, rock softening, dilatancy and a small Young’s modulus in the plastic zone. The Vlachopoulos’s formula due to its rationality is adopted to determine the relief ratio of longitudinal deformation of the tunnel . The support pressure differences anticipated from the convergence – confinement analysis between two methods for determining the initial location of support action are discussed. The results show that the influence of the unified strength theory parameter on the ground reaction curve and longitudinal deformation profile of the tunnel is significant. The strength potentials of rock mass are better achieved due to considering the effect of the intermediate principal stress. The effects of Young’s modulus in the plastic zone and dilatancy on the ground reaction curve are important. The differences of support pressure between two methods for determining the initial location of support action are remarkable.
Based on the unified strength theory and a non-associated flow rule , a new analytical solution for ground reaction curve of a deep circular rock tunnel is presented taking into consideration the integrated effects of the intermediate principal stress, rock softening, dilatancy and a small Young’s modulus in the plastic zone. The Vlachopoulos’s formula due to its rationality is adopted to determine the relief ratio of longitudinal deformation of the tunnel . The support pressure differences anticipated from the convergence – confinement analysis between two methods for determining the initial location of support action are discussed. The results show that the influence of the unified strength theory parameter on the ground reaction curve and longitudinal deformation profile of the tunnel is significant. The strength potentials of rock mass are better achieved due to considering the effect of the intermediate principal stress. The effects of Young’s modulus in the plastic zone and dilatancy on the ground reaction curve are important. The differences of support pressure between two methods for determining the initial location of support action are remarkable.
Abstract：
It is effective to detect the thickness and lacuna of artificial freezing walls by means of the ground penetrating radarGPR). Based on the physical model tests, the similarity criteria of GPR exploration are derived for artificial freezing projects, which have clear physical meanness and can be employed to explain the relationship of the propagation time and amplitude of GPR signals between the model and the prototype. According to the electromagnetic properties of freezing soils with different frequencies, the similar criterion is a contradictory one in GPR model for the artificial freezing projects. It is deduced that in AFE the travel time and characters of anomalies in GPR profiles are similar to those of the prototypes, while the amplitude of GPR signals will be much stronger than that of the prototypes. Through model tests and field explorations, the characteristics of typical anomalies in AFE, such as freezing pipe and defects, are obtained and reported. It is found that they play an important role in the construction of the connecting passage of Shanghai Yangtze River Tunnel. The research findings have an important theoretical value for the GPR experimental study and can be used in artificial freezing projects and engineering construction in permafrost regions.
It is effective to detect the thickness and lacuna of artificial freezing walls by means of the ground penetrating radarGPR). Based on the physical model tests, the similarity criteria of GPR exploration are derived for artificial freezing projects, which have clear physical meanness and can be employed to explain the relationship of the propagation time and amplitude of GPR signals between the model and the prototype. According to the electromagnetic properties of freezing soils with different frequencies, the similar criterion is a contradictory one in GPR model for the artificial freezing projects. It is deduced that in AFE the travel time and characters of anomalies in GPR profiles are similar to those of the prototypes, while the amplitude of GPR signals will be much stronger than that of the prototypes. Through model tests and field explorations, the characteristics of typical anomalies in AFE, such as freezing pipe and defects, are obtained and reported. It is found that they play an important role in the construction of the connecting passage of Shanghai Yangtze River Tunnel. The research findings have an important theoretical value for the GPR experimental study and can be used in artificial freezing projects and engineering construction in permafrost regions.
Abstract：
A non-intrusive finite element method for the reliability analysis of deformation for underground rock caverns is proposed. First, the polynomial chaos expansion is introduced. The software SIGMA/W is selected to perform the deterministic FEM analysis. Thereafter, a procedure for the interface between stochastic analysis module and software SIGMA/W is presented, and a flowchart is provided as well. The non-intrusive finite element method means there is no need for user-intervention during the calculation of the deterministic finite element code while the normal stochastic finite element methods always do. This is of practical advantage that realistic probabilistic analyses become possible for the practitioners. The computational efficiency of the proposed method is significantly higher than that of the traditional Monte Carlo simulation. It can serve as an alternate method for the reliability analysis of complex geotechnical problems. The liner supporting can improve the reliability of the underground rock caverns effectively. The sensitivity results indicate that the elastic modulus is the most significant random variable, whereas the unit weight almost has no influence on the reliability results. Therefore, to improve the reliability of the underground rock caverns effectively, a detailed geological investigation should be conducted to reduce the uncertainty in the elastic modulus of rock mass.
A non-intrusive finite element method for the reliability analysis of deformation for underground rock caverns is proposed. First, the polynomial chaos expansion is introduced. The software SIGMA/W is selected to perform the deterministic FEM analysis. Thereafter, a procedure for the interface between stochastic analysis module and software SIGMA/W is presented, and a flowchart is provided as well. The non-intrusive finite element method means there is no need for user-intervention during the calculation of the deterministic finite element code while the normal stochastic finite element methods always do. This is of practical advantage that realistic probabilistic analyses become possible for the practitioners. The computational efficiency of the proposed method is significantly higher than that of the traditional Monte Carlo simulation. It can serve as an alternate method for the reliability analysis of complex geotechnical problems. The liner supporting can improve the reliability of the underground rock caverns effectively. The sensitivity results indicate that the elastic modulus is the most significant random variable, whereas the unit weight almost has no influence on the reliability results. Therefore, to improve the reliability of the underground rock caverns effectively, a detailed geological investigation should be conducted to reduce the uncertainty in the elastic modulus of rock mass.
Abstract：
The c ement stabilized soil in natural condition, as well as stabilization in corrosive site, will be influenced by e nvironmental pollution such as acid rain, seawater invasion or industrial pollution, which will lead to deterioration of the structure. Especially in the corrosive site, the strength of soil stabilized by cement will increase, but at the same time, it will decrease due to the deterioration at the beginning of stabilization. Th e experimental work is performed to study the strength of soil stabilized by cement in the corrosive site which is represented by sea water. Laboratory tests a re carried out to measure the strength distribution by means of the micro cone penetration test s . Also, the element analysis test s using the ion chromatography to measure the distribution of Ca2+ within the specimen a re conducted. The effect of seawater pressure o n the strength of cement stabilized marine clay is analyzed . Two conditions a re prepared. In t he first condition, two meters of seawater pressure are applied to the specimen by using vertical pipe filled by seawater, and the other specimen has no pressure applied. It is indicated that the deterioration extend s quickly under seawater environment and the deteriorated depth bec om e s deeper with the increase of pressure . The element analysis show s that the concentration of calcium ion s in deteriorated portion is lower than that in non deteriorated portion.
The c ement stabilized soil in natural condition, as well as stabilization in corrosive site, will be influenced by e nvironmental pollution such as acid rain, seawater invasion or industrial pollution, which will lead to deterioration of the structure. Especially in the corrosive site, the strength of soil stabilized by cement will increase, but at the same time, it will decrease due to the deterioration at the beginning of stabilization. Th e experimental work is performed to study the strength of soil stabilized by cement in the corrosive site which is represented by sea water. Laboratory tests a re carried out to measure the strength distribution by means of the micro cone penetration test s . Also, the element analysis test s using the ion chromatography to measure the distribution of Ca2+ within the specimen a re conducted. The effect of seawater pressure o n the strength of cement stabilized marine clay is analyzed . Two conditions a re prepared. In t he first condition, two meters of seawater pressure are applied to the specimen by using vertical pipe filled by seawater, and the other specimen has no pressure applied. It is indicated that the deterioration extend s quickly under seawater environment and the deteriorated depth bec om e s deeper with the increase of pressure . The element analysis show s that the concentration of calcium ion s in deteriorated portion is lower than that in non deteriorated portion.
2012, 34(1): 139-144.
Abstract：
By using the dynamic finite element stability and deformation method, the definite methods for the most dangerous sliding surface, the influences of seismic duration and depth of sliding surface on slope stability and deformation as well as the reinforcement range of dam slopes are studied. The results show that by means of the pseudo-static method, the slip circle corresponding to the minimum safety factor is deeper and the slip range is larger owing to the fact that the acceleration distribution coefficient suggested by the Chinese Code does not match the seismic response of dams. It is not helpful for determining the reinforcement range of dam slopes. During the earthquake history, the potential sliding surface varies with the time history, and it should be arbitrarily searched by using the dynamic finite element method. The potential sliding surface corresponding to the minimum safety factor is different from the maximum slippage. The estimation of the stability safety of dam slopes should combine the safety factor with the deformation. The reinforcement range of dam slopes is suggested according to the calculated results.
By using the dynamic finite element stability and deformation method, the definite methods for the most dangerous sliding surface, the influences of seismic duration and depth of sliding surface on slope stability and deformation as well as the reinforcement range of dam slopes are studied. The results show that by means of the pseudo-static method, the slip circle corresponding to the minimum safety factor is deeper and the slip range is larger owing to the fact that the acceleration distribution coefficient suggested by the Chinese Code does not match the seismic response of dams. It is not helpful for determining the reinforcement range of dam slopes. During the earthquake history, the potential sliding surface varies with the time history, and it should be arbitrarily searched by using the dynamic finite element method. The potential sliding surface corresponding to the minimum safety factor is different from the maximum slippage. The estimation of the stability safety of dam slopes should combine the safety factor with the deformation. The reinforcement range of dam slopes is suggested according to the calculated results.
Abstract：
Based on the Qingchun Road cross-river tunnel of Hangzhou, frozen parameters and process of long-distance liquid nitrogen freezing in high-confined aquifer are obtained, and field measurements of freezing temperature are performed. The results show that the long-distance liquid nitrogen freezing temperature should be guaranteed in the way when the temperature reaches the working liquid nitrogen below -100℃, and the exit temperature after cycling should be held between - 50℃ ～ - 70℃. By using three 1 cm-thick layers of polyethylene insulating materials and three layers of sealed film alternately, the heat preservation effect is obvious, the package temperature has a rise of 0.070 ℃ / m, and the longest distance for the liquid nitrogen freezing can reach 1000 m. The development speed of permafrost from large to small order is gravel layer> silt sand layer> silt clay layer. The temperature of segment is affected by external environment, and the temperatures at segment-shield shell interface before, during and after welding of shield tail brushes are 5.4℃ ～ - 3.2℃, 19.3℃ ～ 8.7℃ and 12.7℃ ～ 4.8℃ so as to ensure the thawing and welding quality of frozen walls. Compulsory thawing only needs 2 days to achieve the condition for the shield, and this procedure has a total duration of 23 days, which solves the problem of replacing shield tail brushes in confined aquifer.
Based on the Qingchun Road cross-river tunnel of Hangzhou, frozen parameters and process of long-distance liquid nitrogen freezing in high-confined aquifer are obtained, and field measurements of freezing temperature are performed. The results show that the long-distance liquid nitrogen freezing temperature should be guaranteed in the way when the temperature reaches the working liquid nitrogen below -100℃, and the exit temperature after cycling should be held between - 50℃ ～ - 70℃. By using three 1 cm-thick layers of polyethylene insulating materials and three layers of sealed film alternately, the heat preservation effect is obvious, the package temperature has a rise of 0.070 ℃ / m, and the longest distance for the liquid nitrogen freezing can reach 1000 m. The development speed of permafrost from large to small order is gravel layer> silt sand layer> silt clay layer. The temperature of segment is affected by external environment, and the temperatures at segment-shield shell interface before, during and after welding of shield tail brushes are 5.4℃ ～ - 3.2℃, 19.3℃ ～ 8.7℃ and 12.7℃ ～ 4.8℃ so as to ensure the thawing and welding quality of frozen walls. Compulsory thawing only needs 2 days to achieve the condition for the shield, and this procedure has a total duration of 23 days, which solves the problem of replacing shield tail brushes in confined aquifer.
Abstract：
Based on the probability theory, the probability distribution of integrity inspection for piles is analyzed, and the analysis shows that the results of sampling inspection relate to the general unqualified rate and the number of sampling inspectionNSI). Therefore the general unqualified rate is suggested to be the criterion to judge the quality of all the bored piles. The prior distribution of the general qualified rate is deduced to follow the normal Beta distribution using the Bayesian method, and the posterior distribution also follows the Beta distribution according to the conjugate distribution theorem. The expectation and variance of the posterior distribution are studied, consequently. A conclusion is drawn that the posterior expectation is the weighted sum of the current sampling unqualified rate and the prior expectation, and the posterior variance is the current sampling unqualified rate and the prior variance. It is demonstrated through the analysis of the relation between the NSI and the weighted coefficients, and the posterior expectation and variance that the results of sampling inspection are sensitive to the NSI when the NSI is less than ten, but when NSI is greater than ten, especially, greater than twenty, the results of sampling inspection are insensitive to the NSI. Finally, a dynamic evaluation model of the general unqualified rate is established using the relation between the prior expectation and variance and the posterior expectation and variance. The results from the numerical example indicate that the general unqualified rate can be more accurately estimated using the dynamic evaluation model, which is significant in engineering practice.
Based on the probability theory, the probability distribution of integrity inspection for piles is analyzed, and the analysis shows that the results of sampling inspection relate to the general unqualified rate and the number of sampling inspectionNSI). Therefore the general unqualified rate is suggested to be the criterion to judge the quality of all the bored piles. The prior distribution of the general qualified rate is deduced to follow the normal Beta distribution using the Bayesian method, and the posterior distribution also follows the Beta distribution according to the conjugate distribution theorem. The expectation and variance of the posterior distribution are studied, consequently. A conclusion is drawn that the posterior expectation is the weighted sum of the current sampling unqualified rate and the prior expectation, and the posterior variance is the current sampling unqualified rate and the prior variance. It is demonstrated through the analysis of the relation between the NSI and the weighted coefficients, and the posterior expectation and variance that the results of sampling inspection are sensitive to the NSI when the NSI is less than ten, but when NSI is greater than ten, especially, greater than twenty, the results of sampling inspection are insensitive to the NSI. Finally, a dynamic evaluation model of the general unqualified rate is established using the relation between the prior expectation and variance and the posterior expectation and variance. The results from the numerical example indicate that the general unqualified rate can be more accurately estimated using the dynamic evaluation model, which is significant in engineering practice.
Abstract：
Based on the side-crossing construction of Shanghai Metro line No. 11 close to the ancient architectures, numerical simulation and field monitoring are employed to study the settlement of the adjacent ancient architectures induced by the construction of MJS piles and the side-crossing of newly shield-driven tunnel. The influences on the buildings during the whole construction process can be divided into three stages: disturbance of pre-reinforced piles and crossing of up and down lines. The stage of pre-construction of MJS piles has the most remarkable impact. Due to the protection of MJS piles, the stages of crossing of up and down lines have the second largest and the smallest impacts, respectively. In addition, because of the construction of piles and the existing buildings at the left side of the tunnel, the settlement trough differs from the traditional one, and the distribution of horizontal displacement obviously changes. Moreover, due to the protection of isolation piles, the settlement produced by shield driving greatly decreases. Finally, the field monitoring data agree with the numerical results. The accuracy and rationality of the numerical simulation method is validated.
Based on the side-crossing construction of Shanghai Metro line No. 11 close to the ancient architectures, numerical simulation and field monitoring are employed to study the settlement of the adjacent ancient architectures induced by the construction of MJS piles and the side-crossing of newly shield-driven tunnel. The influences on the buildings during the whole construction process can be divided into three stages: disturbance of pre-reinforced piles and crossing of up and down lines. The stage of pre-construction of MJS piles has the most remarkable impact. Due to the protection of MJS piles, the stages of crossing of up and down lines have the second largest and the smallest impacts, respectively. In addition, because of the construction of piles and the existing buildings at the left side of the tunnel, the settlement trough differs from the traditional one, and the distribution of horizontal displacement obviously changes. Moreover, due to the protection of isolation piles, the settlement produced by shield driving greatly decreases. Finally, the field monitoring data agree with the numerical results. The accuracy and rationality of the numerical simulation method is validated.
Abstract：
By using the soil static and dynamic universal tri-axial and torsional shear apparatus, the stress-controlled undrained static torsional tests are performed on Dongying intact saturated silt of Shandong province and remolding saturated silt prepared by tamping method controlling three kinds of the initial sampling water contents. The conditions of the initial anisotropic consolidation are the initial mean principal stress of 100 kPa, the initial intermediate principal stress coefficient of 0.5, the initial deviator stress ratio 0.433 and the initial orientation angle of the principal stress respectively at 0o, 30o, 45o, 60o, 90o. During the undrained monotonic shearing process, the mean principal stress and the intermediate principal stress coefficient are fixed. The effects of orientation of the initial principal stress and initial sampling water content on the stress-strain relations, the pore pressure development as well as the effective stress paths are studied. The test results show that the effect degree of the initial principal stress orientation on deformation and strength behavior of intact silt is different from that of the remolding silt. The initial sampling water content has considerable influence on the test results of the saturated remolding silt.
By using the soil static and dynamic universal tri-axial and torsional shear apparatus, the stress-controlled undrained static torsional tests are performed on Dongying intact saturated silt of Shandong province and remolding saturated silt prepared by tamping method controlling three kinds of the initial sampling water contents. The conditions of the initial anisotropic consolidation are the initial mean principal stress of 100 kPa, the initial intermediate principal stress coefficient of 0.5, the initial deviator stress ratio 0.433 and the initial orientation angle of the principal stress respectively at 0o, 30o, 45o, 60o, 90o. During the undrained monotonic shearing process, the mean principal stress and the intermediate principal stress coefficient are fixed. The effects of orientation of the initial principal stress and initial sampling water content on the stress-strain relations, the pore pressure development as well as the effective stress paths are studied. The test results show that the effect degree of the initial principal stress orientation on deformation and strength behavior of intact silt is different from that of the remolding silt. The initial sampling water content has considerable influence on the test results of the saturated remolding silt.
Abstract：
Aiming at simplifying the application of the Culmann’s graphical construction in fold line slopes , the bio-fold and tri-fold line slopes behind the retaining wall are taken as the analytical models based on Wang Kuihua’s amelioration on straight line slopes. According to the Coulomb’s earth pressure theory and the similarity between the geometric triangle and the force vector triangle, a new graphical method is developed. Compared with the Culmann’s graphical construction, the newly ameliorated approach needn’t calculate the weight of the slide masses, and either needn’t measure the line segments out proportionally to present the weight of the slide masses. The proposed approach needs fewer calculations and is more convenient, and the results are more precise.
Aiming at simplifying the application of the Culmann’s graphical construction in fold line slopes , the bio-fold and tri-fold line slopes behind the retaining wall are taken as the analytical models based on Wang Kuihua’s amelioration on straight line slopes. According to the Coulomb’s earth pressure theory and the similarity between the geometric triangle and the force vector triangle, a new graphical method is developed. Compared with the Culmann’s graphical construction, the newly ameliorated approach needn’t calculate the weight of the slide masses, and either needn’t measure the line segments out proportionally to present the weight of the slide masses. The proposed approach needs fewer calculations and is more convenient, and the results are more precise.
Abstract：
A method for simulating the static loading test on a single pile is established based on the Mindlin’s settlement solution, including surcharge loading tests and anchor pile loading tests. The two kinds of test load are compared, and the factors for the test results are analyzed. The influences of arrangement of a bridge with temporary supports or anchor piles on the static loading tests on a single pile are emphasized. The results show that the surcharge and archor pile loading tests exaggerate the pile rigidity, and the exaggeration of the former is less than that of the latter. Additionally the static loading tests according to the Chinese code in some conditions will cause more errors. Therefore the interaction of the uprising of datum piles due to unloading of the bridge with temporary supports or pulling of anchor-pile and lowering of datum piles due to loading of test piles may be fully used to decrease the influences on the results.
A method for simulating the static loading test on a single pile is established based on the Mindlin’s settlement solution, including surcharge loading tests and anchor pile loading tests. The two kinds of test load are compared, and the factors for the test results are analyzed. The influences of arrangement of a bridge with temporary supports or anchor piles on the static loading tests on a single pile are emphasized. The results show that the surcharge and archor pile loading tests exaggerate the pile rigidity, and the exaggeration of the former is less than that of the latter. Additionally the static loading tests according to the Chinese code in some conditions will cause more errors. Therefore the interaction of the uprising of datum piles due to unloading of the bridge with temporary supports or pulling of anchor-pile and lowering of datum piles due to loading of test piles may be fully used to decrease the influences on the results.
Abstract：
The problems and solutions of applying the bender element method to determine the maximum shear modulus Gmax) of sand are investigated by conducting resonant columnRC) and bender elementBE) tests on four dry sands obtained from Germany. The study indicates that the start-to-start method is more reliable to identify the time of shear wave propagation in specimens compared to other methods. In BE tests, the excitation frequency of input waves has influence on the tested Gmax, and this influence is dependent on soil types and reduced by increasing confining pressure. A comparison between RC and BE tests shows that Gmax by both methods may be well expressed as a linear equation; for the Berlin sand and Braunschweig coarse sand, there exists a threshold Gmax below which Gmax by BE tests GmaxBE)) is greater than that by RC tests GmaxRC)), however beyond which the GmaxBE) is smaller than GmaxRC) and the distance between both increases with increasing stiffness soil. In practice, it is suggested that the input voltage with proper high frequency is preferred for BE tests, as compared with RC tests.
The problems and solutions of applying the bender element method to determine the maximum shear modulus Gmax) of sand are investigated by conducting resonant columnRC) and bender elementBE) tests on four dry sands obtained from Germany. The study indicates that the start-to-start method is more reliable to identify the time of shear wave propagation in specimens compared to other methods. In BE tests, the excitation frequency of input waves has influence on the tested Gmax, and this influence is dependent on soil types and reduced by increasing confining pressure. A comparison between RC and BE tests shows that Gmax by both methods may be well expressed as a linear equation; for the Berlin sand and Braunschweig coarse sand, there exists a threshold Gmax below which Gmax by BE tests GmaxBE)) is greater than that by RC tests GmaxRC)), however beyond which the GmaxBE) is smaller than GmaxRC) and the distance between both increases with increasing stiffness soil. In practice, it is suggested that the input voltage with proper high frequency is preferred for BE tests, as compared with RC tests.
Abstract：
Alkali substances, such as cement and lime, have been largely used to reinforce soil structure. But the laterite has been chronically eroded by alkali materials. Based on the chemical analysis of mutual deterioration of the materials, accelerated life dip in calcium hydroxide is designed for the laterite. The hydraulic factors are compared and the ion concentrations of seepage are tested. The test results show that the alkali substances reduce the cohesion of sesquioxides, depletes the clay particles of the laterite, and leads to poor-gradation of soil. Mutual deterioration of alkali reinforcement materials and acidic laterite is released. The leakage mechanism of contact zone is found for the acid and alkali materials. It is helpful for the strengthening of laterite dams.
Alkali substances, such as cement and lime, have been largely used to reinforce soil structure. But the laterite has been chronically eroded by alkali materials. Based on the chemical analysis of mutual deterioration of the materials, accelerated life dip in calcium hydroxide is designed for the laterite. The hydraulic factors are compared and the ion concentrations of seepage are tested. The test results show that the alkali substances reduce the cohesion of sesquioxides, depletes the clay particles of the laterite, and leads to poor-gradation of soil. Mutual deterioration of alkali reinforcement materials and acidic laterite is released. The leakage mechanism of contact zone is found for the acid and alkali materials. It is helpful for the strengthening of laterite dams.
