2008 Vol. 30 No. 10
Abstract：
Based on the Winkler model,the load transfer matrixes of single pile in elastic and elasto-plastic state in layered soil were presented to obtain the simplified nonlinear method for analysis of settlement and internal force of single pile.The sheltering effect between passive piles and soil was taken into account to modify the conventional interaction factor between two piles.The approximate approach with the concept of the interaction factor was employed to study the nonlinear behavior of pile groups with rigid cap and piled raft foundation.Because the nonhomogeneity of soil and nonlinear interaction between piles and soil was considered,the theoretical model agreed with the fact quite well.The calculated results was compared with those of the finite element and field tests,and the feasibility of the proposed model for the analysis of pile groups and piled raft foundation was proved.
Based on the Winkler model,the load transfer matrixes of single pile in elastic and elasto-plastic state in layered soil were presented to obtain the simplified nonlinear method for analysis of settlement and internal force of single pile.The sheltering effect between passive piles and soil was taken into account to modify the conventional interaction factor between two piles.The approximate approach with the concept of the interaction factor was employed to study the nonlinear behavior of pile groups with rigid cap and piled raft foundation.Because the nonhomogeneity of soil and nonlinear interaction between piles and soil was considered,the theoretical model agreed with the fact quite well.The calculated results was compared with those of the finite element and field tests,and the feasibility of the proposed model for the analysis of pile groups and piled raft foundation was proved.
Abstract：
An effective stress calculation formula for coal containing gas is proposed coupling with the swelling stress of gas adsorption in the effective stress principle for porous media.Considering the variation of the porosity and permeability of coal containing gas at differential deformation stages,a dynamic model for porosity and permeability is developed based on the previous research results.Furthermore,taking coal containing gas as a kind of isotropic elastoplastic material and taking into account the effect of gas adsorption,the stress and seepage equations are derived and,the solid-gas coupling model for coal containing gas is constructed,which is appropriate to describe the skeleton deformability of coal containing gas and the compressibility of gas under the solid-gas interaction condition.In addition,the numerical simulation model is built by using the finite element method,and the numerical solution of the model for a special loading case is given in term of the constraint conditions and corresponding parameters.The research results maybe have a meaning for further enriching and improving solid-gas coupling theories for coal containing gas.
An effective stress calculation formula for coal containing gas is proposed coupling with the swelling stress of gas adsorption in the effective stress principle for porous media.Considering the variation of the porosity and permeability of coal containing gas at differential deformation stages,a dynamic model for porosity and permeability is developed based on the previous research results.Furthermore,taking coal containing gas as a kind of isotropic elastoplastic material and taking into account the effect of gas adsorption,the stress and seepage equations are derived and,the solid-gas coupling model for coal containing gas is constructed,which is appropriate to describe the skeleton deformability of coal containing gas and the compressibility of gas under the solid-gas interaction condition.In addition,the numerical simulation model is built by using the finite element method,and the numerical solution of the model for a special loading case is given in term of the constraint conditions and corresponding parameters.The research results maybe have a meaning for further enriching and improving solid-gas coupling theories for coal containing gas.
Abstract：
A 3D simulation model considering the shear deformation between the high pre-stressed yield bolts and the rock was suggested,and the corresponding program of the finite element method was developed.Due to simulating bolts with the 2-noded member elements and the 4-noded bolt elements,the proposed method could be used for the simulation of anchorage cables,general bolts and piles.And it could simulate the mechanical properties of the high prestressed yield bolts well.
A 3D simulation model considering the shear deformation between the high pre-stressed yield bolts and the rock was suggested,and the corresponding program of the finite element method was developed.Due to simulating bolts with the 2-noded member elements and the 4-noded bolt elements,the proposed method could be used for the simulation of anchorage cables,general bolts and piles.And it could simulate the mechanical properties of the high prestressed yield bolts well.
2008, 30(10): 1444-1448.
Abstract：
To apply the safety factor of three-dimensional slope stability into the design of gravity dams,the reliability of deep slide was studied.The reliability index was calculated using the Rosenbleuth method,where the safety factor was obtained by use of the three-dimensional limit analysis method of slope stability.It was indicated that the three-dimensional slope stability could be explained by the failure probability through the reliability index.
To apply the safety factor of three-dimensional slope stability into the design of gravity dams,the reliability of deep slide was studied.The reliability index was calculated using the Rosenbleuth method,where the safety factor was obtained by use of the three-dimensional limit analysis method of slope stability.It was indicated that the three-dimensional slope stability could be explained by the failure probability through the reliability index.
Abstract：
True triaxial tests on specimens of gravel were performed,in which σ3 was invariable,and σ1,σ2 were loaded at the same time in a certain proportion b [=(σ2-σ3)/(σ1-σ3)].The influences of the intermediate principal stress on three principal strains and strength were studied separately.Mohr-Coulomb Criterion,Lade-Duncan Criterion,Matsuoka-Nakai Criterion and Fang Kai-ze Criterion were compared with the true triaxial test results of gravel.It was found that the relationships between friction angle and b reflected by Matsuoka-Nakai Criterion and Fang Kai-ze Criterion were different from those of the experimental results,and the laws reflected by Lade-Duncan Criterion were close to those of the experimental results,while it overrated the influence of b on the friction angle.Hence a criterion was proposed,and the relationship between the friction angle and b was deduced and verified using several true triaxial test results.It was indicated that the proposed criterion could reflect the relationship between the friction angle and b more accurately than Lade-Duncan Criterion and Matsuoka-Nakai Criterion.
True triaxial tests on specimens of gravel were performed,in which σ3 was invariable,and σ1,σ2 were loaded at the same time in a certain proportion b [=(σ2-σ3)/(σ1-σ3)].The influences of the intermediate principal stress on three principal strains and strength were studied separately.Mohr-Coulomb Criterion,Lade-Duncan Criterion,Matsuoka-Nakai Criterion and Fang Kai-ze Criterion were compared with the true triaxial test results of gravel.It was found that the relationships between friction angle and b reflected by Matsuoka-Nakai Criterion and Fang Kai-ze Criterion were different from those of the experimental results,and the laws reflected by Lade-Duncan Criterion were close to those of the experimental results,while it overrated the influence of b on the friction angle.Hence a criterion was proposed,and the relationship between the friction angle and b was deduced and verified using several true triaxial test results.It was indicated that the proposed criterion could reflect the relationship between the friction angle and b more accurately than Lade-Duncan Criterion and Matsuoka-Nakai Criterion.
Abstract：
A series of physical simulation experiments for pile groups with varying rigidity and those with uniformly distributed piles under static axial load were done,and the test results were analyzed and compared.It was indicated that for the displacement distribution type of the pile group with varying rigidity the displacement of the side piles was larger than that of middle piles,this was quite the contrary of uniformly distributed piles.The total settlement increased slightly and differential settlement decreased markedly.Increasing the length of middle pile could increase the bearing capacity both of the pile groups and soils under the pile cap for varying rigidity pile groups,indicating that the bearing capacity of the side piles was latent in uniformly distributed piles.The shaft friction developed along the lower part to the middle of the pile in pile groups,different from that of single pile.The less the pile spacing,the more obvious this trend.
A series of physical simulation experiments for pile groups with varying rigidity and those with uniformly distributed piles under static axial load were done,and the test results were analyzed and compared.It was indicated that for the displacement distribution type of the pile group with varying rigidity the displacement of the side piles was larger than that of middle piles,this was quite the contrary of uniformly distributed piles.The total settlement increased slightly and differential settlement decreased markedly.Increasing the length of middle pile could increase the bearing capacity both of the pile groups and soils under the pile cap for varying rigidity pile groups,indicating that the bearing capacity of the side piles was latent in uniformly distributed piles.The shaft friction developed along the lower part to the middle of the pile in pile groups,different from that of single pile.The less the pile spacing,the more obvious this trend.
2008, 30(10): 1460-1466.
Abstract：
With regard to the uplift anomaly phenomenon occurred in the right abutment of Lijiaxia Dam in China,a three-dimensional finite element model for seepage of the dam and its foundation was established.The methods of modeling the seepage prevention curtains were introduced.The drainage holes were modeled as so-called drainage sub-structures.Then an approach of back analysis for seepage parameters based on artificial neural network was proposed.The back analysis was conducted and the permeability tensors of the rock masses were obtained.The three-dimensional finite element analysis of seepage flow through the dam and its foundation was performed.Using the analytic results the influence of various factors such as seepage prevention measures,drainage and geologic conditions in the seepage field was evaluated,and then the cause of uplift anomaly was investigated combined with the results of the drilling and water quality tests in the foundation.It was shown that anomaly phenomenon was due to the grout curtain defects and leakage channel exiting in the shallow foundation.
With regard to the uplift anomaly phenomenon occurred in the right abutment of Lijiaxia Dam in China,a three-dimensional finite element model for seepage of the dam and its foundation was established.The methods of modeling the seepage prevention curtains were introduced.The drainage holes were modeled as so-called drainage sub-structures.Then an approach of back analysis for seepage parameters based on artificial neural network was proposed.The back analysis was conducted and the permeability tensors of the rock masses were obtained.The three-dimensional finite element analysis of seepage flow through the dam and its foundation was performed.Using the analytic results the influence of various factors such as seepage prevention measures,drainage and geologic conditions in the seepage field was evaluated,and then the cause of uplift anomaly was investigated combined with the results of the drilling and water quality tests in the foundation.It was shown that anomaly phenomenon was due to the grout curtain defects and leakage channel exiting in the shallow foundation.
Abstract：
The consolidation in saturated orthogonal anisotropic soil among group-piles was studied.Considering the initial distribution and the boundary conditions of excess pore water pressure caused by group-piles,the space consolidation model was established and the progression solutions could be found by using methods of mathematical physics in enclosed field.The solutions could give the results of consolidation degree and pore-water pressure at any point at any time.When the initial distribution of pore pressure was constant and the soil was isotropic,the reasonableness of the solutions was proved by the progression solutions,which could be degenerated to Terzaghi’s one-dimensional consolidation solutions.Finally,practical engineering case was presented to illustrate the results and laws of the soil consolidation.
The consolidation in saturated orthogonal anisotropic soil among group-piles was studied.Considering the initial distribution and the boundary conditions of excess pore water pressure caused by group-piles,the space consolidation model was established and the progression solutions could be found by using methods of mathematical physics in enclosed field.The solutions could give the results of consolidation degree and pore-water pressure at any point at any time.When the initial distribution of pore pressure was constant and the soil was isotropic,the reasonableness of the solutions was proved by the progression solutions,which could be degenerated to Terzaghi’s one-dimensional consolidation solutions.Finally,practical engineering case was presented to illustrate the results and laws of the soil consolidation.
Abstract：
Rock was a kind of typical inhomogeneous brittle material abundant in various deficiencies such as microcracks,gaps and joints and would generate a large quantity of acoustic emission signals during damage process under loading.Application of locating techniques with acoustic emission to monitoring rock damage was a good method to study 3D spatial evolutional pattern of microcrack initiation,propagation,expansion and breakthrough during rock failure process.The Geiger locating algorithm was used to verify the locating precision of acoustic emission generated during rock failure.It was shown that the locating precision of acoustic emission would be much better if the Geiger locating algorithm was applied.The rock acoustic emission system was accurate and could monitor the real-time microcrack propagation.The process of the acoustic emission and rock damage were consistent and the locating results could reflect the process of initial,propagation and breakthrough of microcracks accurately.The locating results of the intact specimens and the samples with pre-cracks were in acordance with the real failure pattern of rock,indicating that it was a good tool to study the rock failure mechanism.
Rock was a kind of typical inhomogeneous brittle material abundant in various deficiencies such as microcracks,gaps and joints and would generate a large quantity of acoustic emission signals during damage process under loading.Application of locating techniques with acoustic emission to monitoring rock damage was a good method to study 3D spatial evolutional pattern of microcrack initiation,propagation,expansion and breakthrough during rock failure process.The Geiger locating algorithm was used to verify the locating precision of acoustic emission generated during rock failure.It was shown that the locating precision of acoustic emission would be much better if the Geiger locating algorithm was applied.The rock acoustic emission system was accurate and could monitor the real-time microcrack propagation.The process of the acoustic emission and rock damage were consistent and the locating results could reflect the process of initial,propagation and breakthrough of microcracks accurately.The locating results of the intact specimens and the samples with pre-cracks were in acordance with the real failure pattern of rock,indicating that it was a good tool to study the rock failure mechanism.
Abstract：
With the process of accelerative industrialization in China,the polluted foundation soil by industrial organizations had become serious environmental geotechnical problems.The properties of foundation soil have been changed by acid and alkali pollution.Soil specimens polluted by acid and alkali of 4 different concentration were artificially prepared.The compressible and deformable properties of polluted soil were studied.It was concluded that the rebound index,coefficient of compressibility and pre-consolidation pressure of polluted soil increased with the increase of the concentration,and the variation of the compression coefficient of soil polluted by acid was greater than that by alkali.All kinds of factors influencing the compressibility of polluted soil were analyzed,including grain-size distribution,plasticity index,moisture content and void ratio.The influence of variation of the compressibility of soil before and after pollution on the evaluation of the polluted foundation soil was studied.
With the process of accelerative industrialization in China,the polluted foundation soil by industrial organizations had become serious environmental geotechnical problems.The properties of foundation soil have been changed by acid and alkali pollution.Soil specimens polluted by acid and alkali of 4 different concentration were artificially prepared.The compressible and deformable properties of polluted soil were studied.It was concluded that the rebound index,coefficient of compressibility and pre-consolidation pressure of polluted soil increased with the increase of the concentration,and the variation of the compression coefficient of soil polluted by acid was greater than that by alkali.All kinds of factors influencing the compressibility of polluted soil were analyzed,including grain-size distribution,plasticity index,moisture content and void ratio.The influence of variation of the compressibility of soil before and after pollution on the evaluation of the polluted foundation soil was studied.
2008, 30(10): 1484-1489.
Abstract：
In engineering projects of landfills,geomembranes were commonly used to isolate waste from the surrounding ground and groundwater in order to minimize the potential groundwater contamination.Subsequent construction of a landfill included the placement of waste layers and soil covers at various heights over the liners.Substantial down-slope shear stresses might be resulted in the geomembranes,leading to the development of significant geomembrane tension which was necessary to be studied so as to ensure the safe use.The relationship between shear stress and displacement for interface between the geomembranes and the clay was divided into three states: elastic,softening and residual strength.Three-state elasto-plastic model was presented to simulate the shear deformation property for the interface,and the governing differential equations of three states were obtained.Because the demarcation points among the three states were unknown,the iterative computation method should be used to compute the tension of geomembranes.Finally,some important factors,including the influence of landfill height and slope gradient on the tension of geomembranes,were studied.
In engineering projects of landfills,geomembranes were commonly used to isolate waste from the surrounding ground and groundwater in order to minimize the potential groundwater contamination.Subsequent construction of a landfill included the placement of waste layers and soil covers at various heights over the liners.Substantial down-slope shear stresses might be resulted in the geomembranes,leading to the development of significant geomembrane tension which was necessary to be studied so as to ensure the safe use.The relationship between shear stress and displacement for interface between the geomembranes and the clay was divided into three states: elastic,softening and residual strength.Three-state elasto-plastic model was presented to simulate the shear deformation property for the interface,and the governing differential equations of three states were obtained.Because the demarcation points among the three states were unknown,the iterative computation method should be used to compute the tension of geomembranes.Finally,some important factors,including the influence of landfill height and slope gradient on the tension of geomembranes,were studied.
Abstract：
Virtual multidimensional internal bonds(VMIB) was a multiscale mechanical model based on the Virtual Internal bond(VIB) theory.From the view of VIB and VMIB,the microstructures of intact materials and cracked materials were consistent in that both the two materials consisted of network constructed by the randomized materials particles and virtual internal bonds in micro scale.For the cracked materials,the distance of material particles at the pre-existing crack was so large that the interaction(bond stiffness) between particles becomes negligible in micro scale,leading to the macro crack.To simulate the pre-existing crack,an initial deformation was assigned to the aggregate of material particles at the pre-existing crack.The assigned initial deformation was large enough to make interaction between material particles negligible,so as to represent the behavior of the pre-existing crack.By use of this method,the effect of the pre-existing crack was incorporated into the constitutive relation of materials,hence,the cracked materials could be described by the uniform constitutive relationship,which made the present method free of the special treatment of cracks on the element discretization level as the conventional continuum mechanics method did.Moreover,the VMIB was discrete at the constitutive level and the failure criterion had been embedded into the constitutive relation by the bond evolution function,so it was free of the problem of remeshing and choice of external fracture criterion when the failure process was simulated.By simulating the fracture process of a square plate containing two parallel pre-existing cracks,the present method is indicated to be capable of representing the fracture propagation and the failure process of multi-cracked rock materials.
Virtual multidimensional internal bonds(VMIB) was a multiscale mechanical model based on the Virtual Internal bond(VIB) theory.From the view of VIB and VMIB,the microstructures of intact materials and cracked materials were consistent in that both the two materials consisted of network constructed by the randomized materials particles and virtual internal bonds in micro scale.For the cracked materials,the distance of material particles at the pre-existing crack was so large that the interaction(bond stiffness) between particles becomes negligible in micro scale,leading to the macro crack.To simulate the pre-existing crack,an initial deformation was assigned to the aggregate of material particles at the pre-existing crack.The assigned initial deformation was large enough to make interaction between material particles negligible,so as to represent the behavior of the pre-existing crack.By use of this method,the effect of the pre-existing crack was incorporated into the constitutive relation of materials,hence,the cracked materials could be described by the uniform constitutive relationship,which made the present method free of the special treatment of cracks on the element discretization level as the conventional continuum mechanics method did.Moreover,the VMIB was discrete at the constitutive level and the failure criterion had been embedded into the constitutive relation by the bond evolution function,so it was free of the problem of remeshing and choice of external fracture criterion when the failure process was simulated.By simulating the fracture process of a square plate containing two parallel pre-existing cracks,the present method is indicated to be capable of representing the fracture propagation and the failure process of multi-cracked rock materials.
Abstract：
By use of the testing method of stress paths,the behavior of construction of artificial freezing derrick foundation was simulated.It was shown by the results of triaxial creep experiments that the frozen soil was obviously dilatancty,and its volume strain should not be neglected.To fully reflect the creep deformation laws of frozen soil under complex stress paths,a nonlinear rheological constitutive model of frozen soil was put forward by using the basic elements.And the model was embedded in FEPG finite element program on the basis of the secondary developing technique for FEM.It was shown by the results of numerical simulation for field measurement that the deformation properties of dilatancy and volume strain of frozen soil could be reflected by the nonlinear rheological constitutive model very well,and it agreed well with the field measurement data,which could be used as references for the calculation and construction of frozen projects.
By use of the testing method of stress paths,the behavior of construction of artificial freezing derrick foundation was simulated.It was shown by the results of triaxial creep experiments that the frozen soil was obviously dilatancty,and its volume strain should not be neglected.To fully reflect the creep deformation laws of frozen soil under complex stress paths,a nonlinear rheological constitutive model of frozen soil was put forward by using the basic elements.And the model was embedded in FEPG finite element program on the basis of the secondary developing technique for FEM.It was shown by the results of numerical simulation for field measurement that the deformation properties of dilatancy and volume strain of frozen soil could be reflected by the nonlinear rheological constitutive model very well,and it agreed well with the field measurement data,which could be used as references for the calculation and construction of frozen projects.
Abstract：
With regard to the problems in the free swell experiments and the evaluation of stabilized expansive soils,the free swell ratio method was introduced to evaluate the swelling capacity of lime and fly ash treated expansive soils.Based on the test results,the good linear relationships among the free swell ratio and the physical property parameters and the commonly used swell-shrinkage property parameters were identified.The possibility of using the free swell ratio in evaluating the swelling capacity of lime or fly ash stabilized expansive soils was shown,and its practicality had been approved through the utilization of the proposed method in practical engineering projects.
With regard to the problems in the free swell experiments and the evaluation of stabilized expansive soils,the free swell ratio method was introduced to evaluate the swelling capacity of lime and fly ash treated expansive soils.Based on the test results,the good linear relationships among the free swell ratio and the physical property parameters and the commonly used swell-shrinkage property parameters were identified.The possibility of using the free swell ratio in evaluating the swelling capacity of lime or fly ash stabilized expansive soils was shown,and its practicality had been approved through the utilization of the proposed method in practical engineering projects.
2008, 30(10): 1510-1513.
Abstract：
According to the characteristics of time-dependent damage and the threshold of accelerating damage,an evolvement equation of creep damage based on non-linear visco-elasto-plastic rheological model was established.Its correctness was validated by the tests on shear rheological results of slates of large and long water transfer tunnel at Jingping Hydropower Ⅱ.It was shown that the non-linear rheological damage model could not only reflect the whole rheology process of rock,but also describe efficiently the primary,stationary and tertiary rheological damages for slates under the conditions of different stresses.
According to the characteristics of time-dependent damage and the threshold of accelerating damage,an evolvement equation of creep damage based on non-linear visco-elasto-plastic rheological model was established.Its correctness was validated by the tests on shear rheological results of slates of large and long water transfer tunnel at Jingping Hydropower Ⅱ.It was shown that the non-linear rheological damage model could not only reflect the whole rheology process of rock,but also describe efficiently the primary,stationary and tertiary rheological damages for slates under the conditions of different stresses.
2008, 30(10): 1514-1519.
Abstract：
Experimental study on the overconsolidated clay under the cyclic principal stress rotation(CPSR) was performed.Emphasis was put on the influence of different overconsolidation conditions on the characteristics of samples during CPSR.It was found that with the increase of the over consolidation ratio,the equivalent dynamic stiffness and dynamic strength of samples during CPSR increased obviously,while these characteristics were independent of the back pressure control condition during overconsolidation.But whether or not the back pressure was kept constant greatly influenced the generation and level of development of negative pore pressure during the following CPSR stage.
Experimental study on the overconsolidated clay under the cyclic principal stress rotation(CPSR) was performed.Emphasis was put on the influence of different overconsolidation conditions on the characteristics of samples during CPSR.It was found that with the increase of the over consolidation ratio,the equivalent dynamic stiffness and dynamic strength of samples during CPSR increased obviously,while these characteristics were independent of the back pressure control condition during overconsolidation.But whether or not the back pressure was kept constant greatly influenced the generation and level of development of negative pore pressure during the following CPSR stage.
Abstract：
In order to discuss process and mechanism of rock-burst in the surrounding rock of horseshoe section caverns,a physical model,800 mm long and 800 mm wide and 200 mm thick with a horseshoe section cavern,was produced with hard brittle physical model materials from orthogonal experiments by the generalized indexes of uniaxial compressive strength(σc),brittleness coefficient(K) and exponential of strike energy(WB).The physical model was tested in the large triaxial model-test machine of geotechnical engineering under the high stress and plane strain condition.It was shown that a rock-burst which was paroxysmal in hard and brittle surrounding rock of horseshoe section cavern occurred during a transitory time in a limited loading-zone under the high stress condition when crack appeared,and that a relatively steady period appeared during relatively long time and a relatively broad loading-zone appeared after the rock-burst,following stress adjusting.The results of physical simulation were basically consistent with the actual engineering situation.
In order to discuss process and mechanism of rock-burst in the surrounding rock of horseshoe section caverns,a physical model,800 mm long and 800 mm wide and 200 mm thick with a horseshoe section cavern,was produced with hard brittle physical model materials from orthogonal experiments by the generalized indexes of uniaxial compressive strength(σc),brittleness coefficient(K) and exponential of strike energy(WB).The physical model was tested in the large triaxial model-test machine of geotechnical engineering under the high stress and plane strain condition.It was shown that a rock-burst which was paroxysmal in hard and brittle surrounding rock of horseshoe section cavern occurred during a transitory time in a limited loading-zone under the high stress condition when crack appeared,and that a relatively steady period appeared during relatively long time and a relatively broad loading-zone appeared after the rock-burst,following stress adjusting.The results of physical simulation were basically consistent with the actual engineering situation.
Abstract：
The unbound aggregate materials were of very strong dynamic structural characteristics in pavement structure.However,the depiction of structural characteristics was qualitative at present.In order to discuss quantitative parameters of structural properties of the unbound aggregate materials the specimens were adopted by use of the surface vibrating method.Water was regarded as the disarranging factor,and unsaturated and saturated specimens were loaded 3000 times at different stress states.According to the failure modes of the unbound aggregate materials based asphalt pavement,the dynamic structural stabilizability,structural changeability and comprehensive structural parameters of the unbound aggregate materials were defined.It was indicated by the test results that was reflected the water stability of filling material by the dynamic structural stabilizability parameter,and the arrangement stability of skeleton materials was depicted by be structural changeability parameter.These two parameters reflected the two respects of the dynamic structural characteristics,when the confining pressure σ3≧150 kPa,the dynamic structural parameter was not sensitive,and it should be determined under small confining pressure.It was feasible to evaluate the structural characteristics of the unbound aggregate materials dynamic by use of the structural parameters.
The unbound aggregate materials were of very strong dynamic structural characteristics in pavement structure.However,the depiction of structural characteristics was qualitative at present.In order to discuss quantitative parameters of structural properties of the unbound aggregate materials the specimens were adopted by use of the surface vibrating method.Water was regarded as the disarranging factor,and unsaturated and saturated specimens were loaded 3000 times at different stress states.According to the failure modes of the unbound aggregate materials based asphalt pavement,the dynamic structural stabilizability,structural changeability and comprehensive structural parameters of the unbound aggregate materials were defined.It was indicated by the test results that was reflected the water stability of filling material by the dynamic structural stabilizability parameter,and the arrangement stability of skeleton materials was depicted by be structural changeability parameter.These two parameters reflected the two respects of the dynamic structural characteristics,when the confining pressure σ3≧150 kPa,the dynamic structural parameter was not sensitive,and it should be determined under small confining pressure.It was feasible to evaluate the structural characteristics of the unbound aggregate materials dynamic by use of the structural parameters.
Abstract：
Based on the generalized potential theory,an elasto-plastic model of multi-potential surface for interface was created.In the model,the soil-structure interface problem was regarded as two-dimensional question in(σn,τ) field,and the vector composed by the plastic strain increment of dε np and dγ p was represented by gradient vectors of two linearly independent potential functions σn and τ,and the plastic state equations were used to replace the traditional field surface.The model parameters could be obtained by uniaxial compression tests and simple shear tests.The method was introduced,and using the parabola and damped exponential curves to simulate the dilatancy of interface,in which the parameters with definite physical meanings and the fitting results with high quality.It was shown that the model,based on a legible mathematical theory and a small quantity of physical hypothesis,could reflect the dilatancy of interface and well simulate the deformation characteristics of interface.
Based on the generalized potential theory,an elasto-plastic model of multi-potential surface for interface was created.In the model,the soil-structure interface problem was regarded as two-dimensional question in(σn,τ) field,and the vector composed by the plastic strain increment of dε np and dγ p was represented by gradient vectors of two linearly independent potential functions σn and τ,and the plastic state equations were used to replace the traditional field surface.The model parameters could be obtained by uniaxial compression tests and simple shear tests.The method was introduced,and using the parabola and damped exponential curves to simulate the dilatancy of interface,in which the parameters with definite physical meanings and the fitting results with high quality.It was shown that the model,based on a legible mathematical theory and a small quantity of physical hypothesis,could reflect the dilatancy of interface and well simulate the deformation characteristics of interface.
Abstract：
Aiming at the features of Wuhan Yangtze River Tunnel,that is,a tunnel under high water pressure and across multi-layered strata with widely different hardness,model tests on segment lining structure with different water and earth pressures under the layered strata and single stratum were performed by jointly applying the simulation facilities of shield tunnel-ground complex and rotary water pressure devices.The effect of mechanical characteristics of segment lining structure for shield tunnels under multi-layered strata was analyzed.It was shown that: with the increase of water pressure,the average axial force of segment lining structure increased evidently,and the maximum bending moment increased slightly or did not changed basically;the bending moment of segment lining in the hard rock stratum obviously decreased;the influence on the maximum internal force of segment lining caused by the hard rock in certain region was slight.These results could provide valuable preference to the design of segment lining structure for Wuhan Yangtze River Tunnel.
Aiming at the features of Wuhan Yangtze River Tunnel,that is,a tunnel under high water pressure and across multi-layered strata with widely different hardness,model tests on segment lining structure with different water and earth pressures under the layered strata and single stratum were performed by jointly applying the simulation facilities of shield tunnel-ground complex and rotary water pressure devices.The effect of mechanical characteristics of segment lining structure for shield tunnels under multi-layered strata was analyzed.It was shown that: with the increase of water pressure,the average axial force of segment lining structure increased evidently,and the maximum bending moment increased slightly or did not changed basically;the bending moment of segment lining in the hard rock stratum obviously decreased;the influence on the maximum internal force of segment lining caused by the hard rock in certain region was slight.These results could provide valuable preference to the design of segment lining structure for Wuhan Yangtze River Tunnel.
Abstract：
The dimensional effect of temperature field in permafrost embankment was a general term for size effect of embankment and structural effect of pavement.Based on the equivalent parameter model of heat-transfer considering phase change of ice and water and moisture transfer,the size effect of embankment with different heights,widths and side slope angles and the structural effect of asphalt pavement,cement concrete pavement and gravel pavement were simulated to analyze variation of embankment temperature field in permafrost regions on the plateau.It was shown that the permafrost was sensitive to dimensional effect of the highway on the Qinghai-Tibet Plateau and the variation of temperature field of embankment was directly influenced by the embankment size.The heat absorption of frozen foundation was negatively dependent on embankment height and side slope,but positively dependent on the embankment width.The influence of heat absorption of asphat parement on the temperature field was about 1.7 times that of gravel parement.According to the research,it could be concluded that the wide embankment and thermal effect of asphalt pavement were the two key factors for the variation of temperature field of frozen soil embankmentcompared with other projects.Therefore,it was necessary to emphasize the engineering stabilization and security problems from the dimensional effect of highway on permafrost foundation in expressway construction on Qinghai-Tibet Plateau in the future.
The dimensional effect of temperature field in permafrost embankment was a general term for size effect of embankment and structural effect of pavement.Based on the equivalent parameter model of heat-transfer considering phase change of ice and water and moisture transfer,the size effect of embankment with different heights,widths and side slope angles and the structural effect of asphalt pavement,cement concrete pavement and gravel pavement were simulated to analyze variation of embankment temperature field in permafrost regions on the plateau.It was shown that the permafrost was sensitive to dimensional effect of the highway on the Qinghai-Tibet Plateau and the variation of temperature field of embankment was directly influenced by the embankment size.The heat absorption of frozen foundation was negatively dependent on embankment height and side slope,but positively dependent on the embankment width.The influence of heat absorption of asphat parement on the temperature field was about 1.7 times that of gravel parement.According to the research,it could be concluded that the wide embankment and thermal effect of asphalt pavement were the two key factors for the variation of temperature field of frozen soil embankmentcompared with other projects.Therefore,it was necessary to emphasize the engineering stabilization and security problems from the dimensional effect of highway on permafrost foundation in expressway construction on Qinghai-Tibet Plateau in the future.
Abstract：
Through the analysis on monitoring data of the deep foundation pit for east-section of Qiutao Road station of Hangzhou Metro,such as horizontal displacement of retaining piles,axial force of steel struts,surface settlements and underground water levels,some valuable conclusions were drawn.It was shown that the deformation characteristics of the retaining structures were related to the horizontal displacement of the retaining piles which was an important criterion for the safety condition of retaining structures.The lateral deformation of the retaining piles was mainly induced by excavation,and was related to exposed time of wall face after excavation.The axial force of the steel struts increased with the increase of the excavation depth,and its value varied with the excavation modes and velocities,air temperatures and dismantlement of the underlying struts.The distributions of the surface settlements in the east of the foundation pit were a parabolic,while those in the south of the foundation pit were triangular.The variation of the underground water levels in the outside of the foundation pit could reflect the watertight effect of the retaining structures.
Through the analysis on monitoring data of the deep foundation pit for east-section of Qiutao Road station of Hangzhou Metro,such as horizontal displacement of retaining piles,axial force of steel struts,surface settlements and underground water levels,some valuable conclusions were drawn.It was shown that the deformation characteristics of the retaining structures were related to the horizontal displacement of the retaining piles which was an important criterion for the safety condition of retaining structures.The lateral deformation of the retaining piles was mainly induced by excavation,and was related to exposed time of wall face after excavation.The axial force of the steel struts increased with the increase of the excavation depth,and its value varied with the excavation modes and velocities,air temperatures and dismantlement of the underlying struts.The distributions of the surface settlements in the east of the foundation pit were a parabolic,while those in the south of the foundation pit were triangular.The variation of the underground water levels in the outside of the foundation pit could reflect the watertight effect of the retaining structures.
Abstract：
Based on the digital image processing technique,a method was presented for microfabric analysis for ideal granular materials composed of metal bars with specified sections.A code named IPFA was then developed to implement the functions such as particle detection,contact searching and microfabric analysis.By use of this method,the digital images of dense samples were firstly enhanced to clear the noises.The particles were then detected from the enhanced images using template matching algorithm presented here,and contact normals between particles were searched based on the particle detection results.Finally,the statistical analysis could be processed on two important elements of microscopic fabric,including directions of the long axis of particles and the contact normals between particles.The proposed method was especially suitable for ideal two-dimensional granular materials,and could be used as a powerful tool for the analysis of microfabric of granular materials and its evaluation because of its high precision and efficiency of particle detection.
Based on the digital image processing technique,a method was presented for microfabric analysis for ideal granular materials composed of metal bars with specified sections.A code named IPFA was then developed to implement the functions such as particle detection,contact searching and microfabric analysis.By use of this method,the digital images of dense samples were firstly enhanced to clear the noises.The particles were then detected from the enhanced images using template matching algorithm presented here,and contact normals between particles were searched based on the particle detection results.Finally,the statistical analysis could be processed on two important elements of microscopic fabric,including directions of the long axis of particles and the contact normals between particles.The proposed method was especially suitable for ideal two-dimensional granular materials,and could be used as a powerful tool for the analysis of microfabric of granular materials and its evaluation because of its high precision and efficiency of particle detection.
Abstract：
With regard to the face-face contact problems,a FEA model of sample drilling was established by adopting the Drucker-Prager rule and regarding soils as DP materials.Through drilling bit-soil contact and impact loading on drilling bits,the drilling process was simulated.The penetration and the effect on soil sampling of the sampling bits were studied by the nonliner transient dynamic analysis of finite element method.It was shown that the axial compression of soil samples was largest on the bit lip surface and was smallest in the center part of the soil samples.The impact disturbance on the soil samples was within a small scope nearby the bits,with the compression ratio of soil samples about 17.7%.
With regard to the face-face contact problems,a FEA model of sample drilling was established by adopting the Drucker-Prager rule and regarding soils as DP materials.Through drilling bit-soil contact and impact loading on drilling bits,the drilling process was simulated.The penetration and the effect on soil sampling of the sampling bits were studied by the nonliner transient dynamic analysis of finite element method.It was shown that the axial compression of soil samples was largest on the bit lip surface and was smallest in the center part of the soil samples.The impact disturbance on the soil samples was within a small scope nearby the bits,with the compression ratio of soil samples about 17.7%.
Abstract：
Based on the FEM for steady seepage,and combining with the analyse of parametric sensitivity and the objective function in optimal design,the construction schedule was taken as the objective function and the overflow hydraulic gradient and the construction time as the restrictive conditions,the optimization of depth of suspended anti-seepage wall in the cofferdam of a hydraulic power station in the Dadu River was performed.Variation of some sensitive parameters including the hydraulic gradient and the schedule with depth of suspended anti-seepage wall was analyzed,and the relationship among them was obtained through the normalization of thinking.The anti-seepage depth was obtained through the restraint condition,and the optimized depth was then yielded.The results were not only necessary for the economy and safety of the engineering construction,but also reasonable for the theorietical basis of the evaluation to suspended cut-off walls.
Based on the FEM for steady seepage,and combining with the analyse of parametric sensitivity and the objective function in optimal design,the construction schedule was taken as the objective function and the overflow hydraulic gradient and the construction time as the restrictive conditions,the optimization of depth of suspended anti-seepage wall in the cofferdam of a hydraulic power station in the Dadu River was performed.Variation of some sensitive parameters including the hydraulic gradient and the schedule with depth of suspended anti-seepage wall was analyzed,and the relationship among them was obtained through the normalization of thinking.The anti-seepage depth was obtained through the restraint condition,and the optimized depth was then yielded.The results were not only necessary for the economy and safety of the engineering construction,but also reasonable for the theorietical basis of the evaluation to suspended cut-off walls.
2008, 30(10): 1569-1574.
Abstract：
According to the comprehensive tests on the rising height of capillary water for twelve kinds of different coarse grained soil and fine grained soil by use of the method of standpipe,the relationship between the rising height of capillary water and time was obtained,and the influencing factors and rules were analyzed.The relationship between the rising height of capillary water of coarse grained soil and time could be drawn by the double-unit regression equation in the logarithmic coordinate.The parameters were related with composition of grain and degree of compaction.The data of the steady rising height of capillary water were obtained,and the regression equation of coarse grained soil on steady height and physical indexes(effective grain d10 and porosity n) was found.Compared with Hazen’s and other expressions that could estimate the steady height of capillary water of coarse grained soil,the proposed method was satisfactory,and the defects of the latter were pointed out.
According to the comprehensive tests on the rising height of capillary water for twelve kinds of different coarse grained soil and fine grained soil by use of the method of standpipe,the relationship between the rising height of capillary water and time was obtained,and the influencing factors and rules were analyzed.The relationship between the rising height of capillary water of coarse grained soil and time could be drawn by the double-unit regression equation in the logarithmic coordinate.The parameters were related with composition of grain and degree of compaction.The data of the steady rising height of capillary water were obtained,and the regression equation of coarse grained soil on steady height and physical indexes(effective grain d10 and porosity n) was found.Compared with Hazen’s and other expressions that could estimate the steady height of capillary water of coarse grained soil,the proposed method was satisfactory,and the defects of the latter were pointed out.
Abstract：
A disastrous M8.0 earthquake happened in Wenchuan,Sichuan Province at 14:28 on May 12,2008.The Yele Dam site was shocked strongly at an epicentral distance of about 258 kilometers.The monitoring station on the dam obtained comparatively complete records of "5.12" Wenchuan Earthquake.Based on the earthquake records of Yele Dam,its seismic response were analyzed by use of the time history method and the spectral analysis method.Combined with the analysis of monitored data of other earthquakes,the effects of the Wenchuan Earthquake on Yele Dam was studied.It was concluded that Yele Dam remained in normal working state after the great Earthquake.Moreover,through the contrastive analysis of dynamic response between "5.12 " Wenchuan earthquake and the previous ones,some distinct seismic response laws of Yele Dam were acquired,and they were closely associated with its peculiar geological condition.
A disastrous M8.0 earthquake happened in Wenchuan,Sichuan Province at 14:28 on May 12,2008.The Yele Dam site was shocked strongly at an epicentral distance of about 258 kilometers.The monitoring station on the dam obtained comparatively complete records of "5.12" Wenchuan Earthquake.Based on the earthquake records of Yele Dam,its seismic response were analyzed by use of the time history method and the spectral analysis method.Combined with the analysis of monitored data of other earthquakes,the effects of the Wenchuan Earthquake on Yele Dam was studied.It was concluded that Yele Dam remained in normal working state after the great Earthquake.Moreover,through the contrastive analysis of dynamic response between "5.12 " Wenchuan earthquake and the previous ones,some distinct seismic response laws of Yele Dam were acquired,and they were closely associated with its peculiar geological condition.
