2006 Vol. 28 No. 1
Abstract：
Unlike other elasto-plastic models of soil,Tsinghua Elasto-plastic Model was developed in a different way,in which the plastic potential surface and the function of the model was directly determined from experimental data without any other assumptions.According to the Drucker’s postulation,the yield function was identical with plastic potential function by selecting proper hardening parameter.The yield locus of the model,formed by 2 circular arcs on π plane,was developed by using true triaxial tests and plane strain tests.A three-dimensional Tsinghua Model was then proposed and the three-dimensional flow rules were presented.Based on the wetting test results of Xiaolangdi rock fill,it was found that as a type of plastic strain,the wetting strain vector was normal to the yield locus of the model.Provided that the model parameters of dry soil and saturated soil and the wetting volumetric strain in isotropic compression test were determined,the whole stress-strain relationship during wetting of the sample could be simulated by the model.An unsaturated soil model was also developed following the similar approach to the wetting Tsinghua Model.In the triaxial test of unsaturated soil,some ice crumbs were mixed into the dry sample before test and the ice crumbs were melted at determined stress states.From the test results it was found that yield surfaces of soil with different moisture contents were the same and hardening parameter was the function of plastic strain and Moisture content.In the Tsinghua Model for unsaturated soil,the strain increment produced by increments of stress and moisture content could be calculated conveniently without appearance of matrix suction.The whole stress-strain relationship in triaxial tests with increasing moisture contents was predicted by the model reasonably.Additionally,based on the behavior observed in triaxial compression tests with dense Yongding River sand,the model was still developed to simulate strain-softening characteristics of the sand,in which the hardening parameter was assumed to be the function of plastic work.The model was verified in computing the displacement vs.load of a shallow footing on dense sand by hydraulic gradient model tests.If the rotational kinematic hardening is applied in the model instead of isotropic hardening,it could be used to model the soil behavior with large stress reversals,by which stress strain relationship during load decreasing or cyclic loading can be simulated.It is thought that Tsinghua Elasto-plastic Model is a promising model for soil.
Unlike other elasto-plastic models of soil,Tsinghua Elasto-plastic Model was developed in a different way,in which the plastic potential surface and the function of the model was directly determined from experimental data without any other assumptions.According to the Drucker’s postulation,the yield function was identical with plastic potential function by selecting proper hardening parameter.The yield locus of the model,formed by 2 circular arcs on π plane,was developed by using true triaxial tests and plane strain tests.A three-dimensional Tsinghua Model was then proposed and the three-dimensional flow rules were presented.Based on the wetting test results of Xiaolangdi rock fill,it was found that as a type of plastic strain,the wetting strain vector was normal to the yield locus of the model.Provided that the model parameters of dry soil and saturated soil and the wetting volumetric strain in isotropic compression test were determined,the whole stress-strain relationship during wetting of the sample could be simulated by the model.An unsaturated soil model was also developed following the similar approach to the wetting Tsinghua Model.In the triaxial test of unsaturated soil,some ice crumbs were mixed into the dry sample before test and the ice crumbs were melted at determined stress states.From the test results it was found that yield surfaces of soil with different moisture contents were the same and hardening parameter was the function of plastic strain and Moisture content.In the Tsinghua Model for unsaturated soil,the strain increment produced by increments of stress and moisture content could be calculated conveniently without appearance of matrix suction.The whole stress-strain relationship in triaxial tests with increasing moisture contents was predicted by the model reasonably.Additionally,based on the behavior observed in triaxial compression tests with dense Yongding River sand,the model was still developed to simulate strain-softening characteristics of the sand,in which the hardening parameter was assumed to be the function of plastic work.The model was verified in computing the displacement vs.load of a shallow footing on dense sand by hydraulic gradient model tests.If the rotational kinematic hardening is applied in the model instead of isotropic hardening,it could be used to model the soil behavior with large stress reversals,by which stress strain relationship during load decreasing or cyclic loading can be simulated.It is thought that Tsinghua Elasto-plastic Model is a promising model for soil.
Abstract：
After a detailed discussion on the transverse effective rigidity ratio of shield tunnel,it was shown that the effective rigidity ratio was always an emperical value.Based on the model test of two-ring tunnel structures and the analysis of the test results,some conclusions could be drawn.The relation of deformation of tunnel structure with the load was clearly linear elastic,so the effective rigidity of shield tunnel was constant in elastic stage,which was agreeable to the rule of the modified conventional design method;the effective rigidity ratios of tunnel with nonstaggered and staggered installation were 0.67 and 0.75 respectively for Shanghai Metro;the effect of soil resistance on the effective rigidity of shield tunnel was very small in soft ground.Compared with empirical formulas and structural tests,the model test could be done conveniently,with abundant believable results and economical cost,and would be a good method to study the effective rigidity of shield tunnels.
After a detailed discussion on the transverse effective rigidity ratio of shield tunnel,it was shown that the effective rigidity ratio was always an emperical value.Based on the model test of two-ring tunnel structures and the analysis of the test results,some conclusions could be drawn.The relation of deformation of tunnel structure with the load was clearly linear elastic,so the effective rigidity of shield tunnel was constant in elastic stage,which was agreeable to the rule of the modified conventional design method;the effective rigidity ratios of tunnel with nonstaggered and staggered installation were 0.67 and 0.75 respectively for Shanghai Metro;the effect of soil resistance on the effective rigidity of shield tunnel was very small in soft ground.Compared with empirical formulas and structural tests,the model test could be done conveniently,with abundant believable results and economical cost,and would be a good method to study the effective rigidity of shield tunnels.
Abstract：
Based on the Biot’s dynamic equations,the vertical vibration of a rigid strip footing rested on saturated soils was studied.By employing the method of Fourier transform,the dynamic governing differential equations for saturated poroelastic medium were solved.Considering the mixed boundary-value conditions at upper surface,a pair of dual integral equations governing the vertical vibration of the rigid strip footing were then derived,which were further converted to linear equations by means of infinite series of orthogonal functions—the Jacobi polynomials.Consequently,the dynamic compliance for saturated soils versus the dimensionless frequency b0 was evaluated.Also,the dynamic compliance for elastic half space versus the dimensionless frequency b0 was studied.Numerical results indicated that,when the dynamic coefficient of permeability was great,its effect on the dynamic compliance must be considered whereas the dynamic coefficient of permeability was small,its effect could be neglected.Moreover the influence of the Poisson’s ratio of soil on the dynamic compliance was little,and the real part and the absolute value of the imaginary part of the dynamic compliance were less than those for elastic half space.
Based on the Biot’s dynamic equations,the vertical vibration of a rigid strip footing rested on saturated soils was studied.By employing the method of Fourier transform,the dynamic governing differential equations for saturated poroelastic medium were solved.Considering the mixed boundary-value conditions at upper surface,a pair of dual integral equations governing the vertical vibration of the rigid strip footing were then derived,which were further converted to linear equations by means of infinite series of orthogonal functions—the Jacobi polynomials.Consequently,the dynamic compliance for saturated soils versus the dimensionless frequency b0 was evaluated.Also,the dynamic compliance for elastic half space versus the dimensionless frequency b0 was studied.Numerical results indicated that,when the dynamic coefficient of permeability was great,its effect on the dynamic compliance must be considered whereas the dynamic coefficient of permeability was small,its effect could be neglected.Moreover the influence of the Poisson’s ratio of soil on the dynamic compliance was little,and the real part and the absolute value of the imaginary part of the dynamic compliance were less than those for elastic half space.
Abstract：
Based on the characteristics of short-duration and abrupt of blasting vibration signals and according to measured data from a practical blast,the features of energy distribution in blasting seismic signals were studied by means of the wavelet packet analysis,which had high resolvability and localization,and energy distribution of blasting seismic signals on different frequency bands was obtained.Based on the relation between characteristic frequency of blasting seismic signals on different frequency bands and natural frequency of controlled structure,the influence of the blasting vibration on the structure could be assessed.A practical engineering example proved that the present method was more effective than the safety-judging standard of single intensity factor for blasting vibration.
Based on the characteristics of short-duration and abrupt of blasting vibration signals and according to measured data from a practical blast,the features of energy distribution in blasting seismic signals were studied by means of the wavelet packet analysis,which had high resolvability and localization,and energy distribution of blasting seismic signals on different frequency bands was obtained.Based on the relation between characteristic frequency of blasting seismic signals on different frequency bands and natural frequency of controlled structure,the influence of the blasting vibration on the structure could be assessed.A practical engineering example proved that the present method was more effective than the safety-judging standard of single intensity factor for blasting vibration.
Abstract：
From the equivalent model of rockmass with one set of joint in local coordinate system suggested by Goodman et al,through the coordinate transformation the equivalent model of rockmass with multi-set joint in global coordinate system was obtained.Using the Goodman’s joint element model and the derived equivalent model respectively,2D FEM analyses were made for the rockmasses with one and two sets of joint under some condition of loading.Finally a numerical simulation for an opening excavation in a jointed rockmass was carried out by applying the derived equivalent model.It could be seen that the results of test and computation were roughly identical,so the effectiveness of the derived equivalent model was shown.
From the equivalent model of rockmass with one set of joint in local coordinate system suggested by Goodman et al,through the coordinate transformation the equivalent model of rockmass with multi-set joint in global coordinate system was obtained.Using the Goodman’s joint element model and the derived equivalent model respectively,2D FEM analyses were made for the rockmasses with one and two sets of joint under some condition of loading.Finally a numerical simulation for an opening excavation in a jointed rockmass was carried out by applying the derived equivalent model.It could be seen that the results of test and computation were roughly identical,so the effectiveness of the derived equivalent model was shown.
Abstract：
Based on Biot dynamic theory for liquid-saturated porous media,the analytical expression and computing method were presented for the seismic wave fields in elastic half-space interbedded by liquid-filled porous medium and solid medium.The theoretical fundamentals were also provided for the input seismic wave fields of underground structures.
Based on Biot dynamic theory for liquid-saturated porous media,the analytical expression and computing method were presented for the seismic wave fields in elastic half-space interbedded by liquid-filled porous medium and solid medium.The theoretical fundamentals were also provided for the input seismic wave fields of underground structures.
Abstract：
The connectivity experiment was carried out to research the source and the flowing of the leakage water in the Kunlunshan Tunnel.The mechanism of leakage was analyzed deeply based on the experimental data,and some opinions were put forward.The basic methods for the treatment scheme has been offered based on the experimental study and analysis.Finally,the formulation and the implementation of the treatment scheme were introduced.It was shown by the measured effect with some means such as the geological radar,etc.that the treatment has reached the anticipated result.
The connectivity experiment was carried out to research the source and the flowing of the leakage water in the Kunlunshan Tunnel.The mechanism of leakage was analyzed deeply based on the experimental data,and some opinions were put forward.The basic methods for the treatment scheme has been offered based on the experimental study and analysis.Finally,the formulation and the implementation of the treatment scheme were introduced.It was shown by the measured effect with some means such as the geological radar,etc.that the treatment has reached the anticipated result.
Abstract：
Shield tunneling has become a main construction method used for underground engineering,especially within weak soil and congested urban areas.With more and more built-up underground projects,it will be often faced with many engineering problems about crossing construction no matter what improvement is made in the tunnel shielding technology.The influence of tunnel shield crossing through an adjacent operating metro was paid much attention by lots of researchers at home and abroad now.A great deal of in-situ monitoring data observed from a case named Zhangyang to Pudian Tunnel No.2 of Shanghai was analyzed and studied.Its conclusion would be helpful for the future similar shield tunneling projects.
Shield tunneling has become a main construction method used for underground engineering,especially within weak soil and congested urban areas.With more and more built-up underground projects,it will be often faced with many engineering problems about crossing construction no matter what improvement is made in the tunnel shielding technology.The influence of tunnel shield crossing through an adjacent operating metro was paid much attention by lots of researchers at home and abroad now.A great deal of in-situ monitoring data observed from a case named Zhangyang to Pudian Tunnel No.2 of Shanghai was analyzed and studied.Its conclusion would be helpful for the future similar shield tunneling projects.
Abstract：
Dynamic responses of vertically vibrating pile were investigated under the axisymmetric condition.A simplified model to study the vertical vibration of pile installed in double layered saturated soil was founded firstly.Then an analytical solution in frequency domain and a semi-analytical solution in time domain were derived.The effects of frost and thaw on the complex stiffness of vertically vibrating pile were analyzed.A viewpoint was proposed that it should be based on the most disadvantageous situation for the dynamic foundation design in permafrost or seasonally frozen regions.For the permafrost,and for the seasonally frozen ground it should be based on the low limit of permafrost and on the unfrozen soil respectively.For the construction of foundation in the permafrost,the frozen soil should be maintained in its original state as rigorously as possible.Finally,the influence of the frost action on the pile test was illustrated.
Dynamic responses of vertically vibrating pile were investigated under the axisymmetric condition.A simplified model to study the vertical vibration of pile installed in double layered saturated soil was founded firstly.Then an analytical solution in frequency domain and a semi-analytical solution in time domain were derived.The effects of frost and thaw on the complex stiffness of vertically vibrating pile were analyzed.A viewpoint was proposed that it should be based on the most disadvantageous situation for the dynamic foundation design in permafrost or seasonally frozen regions.For the permafrost,and for the seasonally frozen ground it should be based on the low limit of permafrost and on the unfrozen soil respectively.For the construction of foundation in the permafrost,the frozen soil should be maintained in its original state as rigorously as possible.Finally,the influence of the frost action on the pile test was illustrated.
Abstract：
Generally,no negative friction is found along pile shafts in static tests.However,negative friction really exists near the surface,as newly backfilled clay is involved.A method was introduced in detail to estimate the average friction along the shaft of bored pile with the assistance of instrumentation of KL re-bar stress meter bonded on the steel cages.On the basis of the calculated average friction,the following conclusions could be drawn.Firstly,negative friction occurs in the range of 0.20.4 pile length from the pile head,and it is mainly induced by consolidation settlement of backfilled clay around the pile head.Secondly,the magnitude of negative friction gradually reduces as getting deeper.Finally,the location of the neutral point,i.e.the location of the zero friction point,keeps changing until deformation of foundation soil becomes stable.
Generally,no negative friction is found along pile shafts in static tests.However,negative friction really exists near the surface,as newly backfilled clay is involved.A method was introduced in detail to estimate the average friction along the shaft of bored pile with the assistance of instrumentation of KL re-bar stress meter bonded on the steel cages.On the basis of the calculated average friction,the following conclusions could be drawn.Firstly,negative friction occurs in the range of 0.20.4 pile length from the pile head,and it is mainly induced by consolidation settlement of backfilled clay around the pile head.Secondly,the magnitude of negative friction gradually reduces as getting deeper.Finally,the location of the neutral point,i.e.the location of the zero friction point,keeps changing until deformation of foundation soil becomes stable.
Abstract：
Deep excavation of Wenzhou Grand Theater was located in the deep silt layer,which was dug 10.55 m in depth.In the design of the protective structure of excavation,the characteristics of the engineering arrangement were well utilized.The soil-nailing wall was the main type of pit-protection structure,meanwhile,some compound types of proctection were adopted,such as soil-nailing with bracing soil-nailing with scattered piles and soil-nailing with rows of piles and struts.The largest displacement monitored in the field,was only 80 mm.Other monitored indexes were all within the standard limit of the design.The design idea and the structural characteristics of the excavation engineering were presented in detail in order to provide reference for the similar engineering projects.
Deep excavation of Wenzhou Grand Theater was located in the deep silt layer,which was dug 10.55 m in depth.In the design of the protective structure of excavation,the characteristics of the engineering arrangement were well utilized.The soil-nailing wall was the main type of pit-protection structure,meanwhile,some compound types of proctection were adopted,such as soil-nailing with bracing soil-nailing with scattered piles and soil-nailing with rows of piles and struts.The largest displacement monitored in the field,was only 80 mm.Other monitored indexes were all within the standard limit of the design.The design idea and the structural characteristics of the excavation engineering were presented in detail in order to provide reference for the similar engineering projects.
Abstract：
It was indicated by numerical analysis and prototype observation that the tensile stress distributed at the left side and right side of face slab of concrete face rockfill dams was usually large and sometimes even larger than tensile strength of concrete.The face slab would crack probably if the tensile stress was larger than the tensile strength of concrete.In order to solve this complex problem,a new idea—broken line type face slab was suggested.Comparison between the stress-strain behavior of broken line type face slab and that of straight line type face slab was made by numerical analysis with three—dimensional finite element method.The calculation results showed that the tensile stress of broken line type face slab was much less than that of straight line type face slab.Moreover,its opening displacement of both the vertical joints and the perimetric joints were also smaller.Therefore,the broken line type face slab could be much safer than the straight line type face slab,especially for high dams or dams in steep-walled valley.
It was indicated by numerical analysis and prototype observation that the tensile stress distributed at the left side and right side of face slab of concrete face rockfill dams was usually large and sometimes even larger than tensile strength of concrete.The face slab would crack probably if the tensile stress was larger than the tensile strength of concrete.In order to solve this complex problem,a new idea—broken line type face slab was suggested.Comparison between the stress-strain behavior of broken line type face slab and that of straight line type face slab was made by numerical analysis with three—dimensional finite element method.The calculation results showed that the tensile stress of broken line type face slab was much less than that of straight line type face slab.Moreover,its opening displacement of both the vertical joints and the perimetric joints were also smaller.Therefore,the broken line type face slab could be much safer than the straight line type face slab,especially for high dams or dams in steep-walled valley.
Abstract：
A new concept – settlement-based design for pile foundations was proposed,which offered a novel alternative to solve the bump problem between bridges and roads.By adjusting pile lengths and pile numbers,the settlement of pile foundation increased from the main span to the side span to such an extent that it matched the settlement of the embankment at both ends of bridges without any special treatment.After construction,a long-term monitoring program on bridge piles and the embankments was performed,which verified the practicability and efficiency of the present method for single braced bridges.The application indicates that the settlement-based design for pile foundations could greatly reduce the total costs by eliminating the necessity of soft soil treatment at embankments and decreasing pile lengths and pile numbers.
A new concept – settlement-based design for pile foundations was proposed,which offered a novel alternative to solve the bump problem between bridges and roads.By adjusting pile lengths and pile numbers,the settlement of pile foundation increased from the main span to the side span to such an extent that it matched the settlement of the embankment at both ends of bridges without any special treatment.After construction,a long-term monitoring program on bridge piles and the embankments was performed,which verified the practicability and efficiency of the present method for single braced bridges.The application indicates that the settlement-based design for pile foundations could greatly reduce the total costs by eliminating the necessity of soft soil treatment at embankments and decreasing pile lengths and pile numbers.
Abstract：
The acoustic emission phenomena of sandstone under the effect of temperature were investigated and discussed in laboratory.There were distinct acoustic emission phenomena in sandstone under the effect of temperature.The rate of acoustic emission had two peak values with the variation of temperature.During 70～90℃,accumulated acoustic emission counts varied rapidly,and it indicated 7090℃ was the threshold for the development of sandstone cracking.
The acoustic emission phenomena of sandstone under the effect of temperature were investigated and discussed in laboratory.There were distinct acoustic emission phenomena in sandstone under the effect of temperature.The rate of acoustic emission had two peak values with the variation of temperature.During 70～90℃,accumulated acoustic emission counts varied rapidly,and it indicated 7090℃ was the threshold for the development of sandstone cracking.
Abstract：
The cut slope might fail without timely support,and the nearby uncut slope could be also affected.If no measures were taken,partial failure of the slope,might cause large scale failure.Based on the above-mentioned,the transition effect due to slope cutting must be considered.The centrifuge model tests of slope cutting indicated that three transition types might be caused.The first was complete failure with tensile crack under low stability;the second was the arc tensile crack failure under high stability;the third was the shallow collapse failure on the cut face in loose material slope.It was found that the radius of curvature of the arc tensile crack increased with the increase of stability of slope,and the tensile crack was related to the distribution of the tensile stress of the in-situ slope.The measured stress and numerical simulation indicated that the whole tensile crack and the arc tensile crack were correspondent to the distribution of maximum tensile stress,the magnitude of which increased due to transition effect.The result was that the transition effect must be considered in low stability slope,but was not necessary in high stability slopes and integrated rock slopes if the creep deformation was not considered.Finally,the formation of arc crack and whole failure transitions were explained with the theory of fractural mechanics.
The cut slope might fail without timely support,and the nearby uncut slope could be also affected.If no measures were taken,partial failure of the slope,might cause large scale failure.Based on the above-mentioned,the transition effect due to slope cutting must be considered.The centrifuge model tests of slope cutting indicated that three transition types might be caused.The first was complete failure with tensile crack under low stability;the second was the arc tensile crack failure under high stability;the third was the shallow collapse failure on the cut face in loose material slope.It was found that the radius of curvature of the arc tensile crack increased with the increase of stability of slope,and the tensile crack was related to the distribution of the tensile stress of the in-situ slope.The measured stress and numerical simulation indicated that the whole tensile crack and the arc tensile crack were correspondent to the distribution of maximum tensile stress,the magnitude of which increased due to transition effect.The result was that the transition effect must be considered in low stability slope,but was not necessary in high stability slopes and integrated rock slopes if the creep deformation was not considered.Finally,the formation of arc crack and whole failure transitions were explained with the theory of fractural mechanics.
Abstract：
Because there was dissension in the maximum principal stress orientation obtained by in-situ stress measurements by different results measurements,the principal stress axis was determined by conjugate joints,fault occurrence,rake angle and shift symbol of fault slip.Plumose fracture and orientation of dislocation was applied to find out whether sharp angle zone or obtuse angle zone between two groups of conjugate joints was compressive zone.The method was applied in Dahuofang reservoir conveying-water engineering and the results indicated that the orientation of the maximum principal stress was nearly EW and identical with the measured data except the measuring points 6,7,8 and 12.The present method could be used to verify whether the measured data was exact or not.
Because there was dissension in the maximum principal stress orientation obtained by in-situ stress measurements by different results measurements,the principal stress axis was determined by conjugate joints,fault occurrence,rake angle and shift symbol of fault slip.Plumose fracture and orientation of dislocation was applied to find out whether sharp angle zone or obtuse angle zone between two groups of conjugate joints was compressive zone.The method was applied in Dahuofang reservoir conveying-water engineering and the results indicated that the orientation of the maximum principal stress was nearly EW and identical with the measured data except the measuring points 6,7,8 and 12.The present method could be used to verify whether the measured data was exact or not.
Abstract：
Through model tests on composite foundation of cement-soil piles under cyclic loading,and with interaction of cushion,reinforced zone and sublayer being taken into account,the vertical permanent deformation of composite foundation of cement-soil piles under cyclic loading was studied and the influences of consolidation states,cyclic stress ratio and vibration frequency were considered.The variation rule of critical cyclic stress ratio and vertical permanent deformation with numbers of loading cycles,vibration frequency and consolidation states were obtained.These results were siginificant to control the settlement of composite foundation.
Through model tests on composite foundation of cement-soil piles under cyclic loading,and with interaction of cushion,reinforced zone and sublayer being taken into account,the vertical permanent deformation of composite foundation of cement-soil piles under cyclic loading was studied and the influences of consolidation states,cyclic stress ratio and vibration frequency were considered.The variation rule of critical cyclic stress ratio and vertical permanent deformation with numbers of loading cycles,vibration frequency and consolidation states were obtained.These results were siginificant to control the settlement of composite foundation.
Abstract：
Many explanations were proposed for the deformation mode of the bank slope.The geological background of Three Gorges was introduced generally at first,and then the unique deformation phenomenon of the slope was serib.Through comprehensive study,it was pointed out that the unique deformation mode of the slope was controlled by the unique structure of the slope.The slope consisted of nearly horizontal layer,with soft layer and hard layer interbedded and perpendicular joints well developed.The strata outcropped in the slope were the second formation and the third formation of Badong group,which belong to middle Triassic system(T).The second formation of Badong group(T2b2) was purplish-red mudstone,which was vulnerable to weather and disintegration,and the third formation of Badong group was brittle and vulnerablion to dissolution.These characteristics of the strata led to deeply remoulding of the structure of the rock mass in the slope,and induced collapse of the structure of the rock mass.Thus,the slope took on some phenomena like slide or slump,and made the deformation mode of the slope complicated.
Many explanations were proposed for the deformation mode of the bank slope.The geological background of Three Gorges was introduced generally at first,and then the unique deformation phenomenon of the slope was serib.Through comprehensive study,it was pointed out that the unique deformation mode of the slope was controlled by the unique structure of the slope.The slope consisted of nearly horizontal layer,with soft layer and hard layer interbedded and perpendicular joints well developed.The strata outcropped in the slope were the second formation and the third formation of Badong group,which belong to middle Triassic system(T).The second formation of Badong group(T2b2) was purplish-red mudstone,which was vulnerable to weather and disintegration,and the third formation of Badong group was brittle and vulnerablion to dissolution.These characteristics of the strata led to deeply remoulding of the structure of the rock mass in the slope,and induced collapse of the structure of the rock mass.Thus,the slope took on some phenomena like slide or slump,and made the deformation mode of the slope complicated.
Abstract：
By use of the method of numerical simulation,the reinforcing mechanism of full-length-bonding pre-stressed cable on pit foundation was studied from two aspects of single cable and group cables.The obtained results were credible compared with the existing conclusion,indicating that the simulation method is relatively reasonable.Finally some experiences of application of numerical method were given.
By use of the method of numerical simulation,the reinforcing mechanism of full-length-bonding pre-stressed cable on pit foundation was studied from two aspects of single cable and group cables.The obtained results were credible compared with the existing conclusion,indicating that the simulation method is relatively reasonable.Finally some experiences of application of numerical method were given.
Abstract：
The California Bearing Ratio(CBR) denoted the potential strength of subgrade material and was an important index to evaluate its performance in expressway.In order to study the main influence factors of the CBR value of clay,the physical and chemical tests of fifteen groups of subgrade materials from the Qingdao-Yinchuan Expressway in Hebei Province were done.Based on the result of tests,that there was obvious difference between CBR values of clays with the same plastic index,the influence factors of CBR of expressway subgrade materials were studied,such as distribution of particle sizes of soils,mineral component and clay mineral component,and useful conclusions were gained.The main influence factors of CBR of expressway subgrade materials were the type and content of minerals component and the shape of distribution curve of particle sizes of soils.The CBR value decreased with the increase of clay-silt ratio.
The California Bearing Ratio(CBR) denoted the potential strength of subgrade material and was an important index to evaluate its performance in expressway.In order to study the main influence factors of the CBR value of clay,the physical and chemical tests of fifteen groups of subgrade materials from the Qingdao-Yinchuan Expressway in Hebei Province were done.Based on the result of tests,that there was obvious difference between CBR values of clays with the same plastic index,the influence factors of CBR of expressway subgrade materials were studied,such as distribution of particle sizes of soils,mineral component and clay mineral component,and useful conclusions were gained.The main influence factors of CBR of expressway subgrade materials were the type and content of minerals component and the shape of distribution curve of particle sizes of soils.The CBR value decreased with the increase of clay-silt ratio.
Abstract：
To study the effect of consolidation stress ratio on soil dynamic strength and dynamic pore water pressure,firstly the related previous research results were reviewed,then the dynamic triaxial tests with saturated gravel samples from the foundation of a rockfill dam were performed.The results of dynamic strength tests showed that there was a turning point of consolidated stress ratio Kc′.When KcKc′,dynamic strength decreased while dynamic deformation and dynamic pore water pressure increased with the increase of Kc.The value of turning point Kc′ depended on the soil properties and stress condition.The approximate value of Kc′ was equal to 2.8 in this test when Kc=0.5～3.0.When Kc=0.7～1.3,final pore water pressure could be equal to confining pressure,and when Kc exceeded or equaled 1.5,the possibility of liquefaction of samples depended on whether the dynamic stress σd could stretch samples or not.
To study the effect of consolidation stress ratio on soil dynamic strength and dynamic pore water pressure,firstly the related previous research results were reviewed,then the dynamic triaxial tests with saturated gravel samples from the foundation of a rockfill dam were performed.The results of dynamic strength tests showed that there was a turning point of consolidated stress ratio Kc′.When Kc
Abstract：
This experiment was based on the embankment of the highway from Changde to Zhangjiajie,which used shale and limestone in its two sections separately.The shear strength indexes of ? and c were obtained for these two embankments,and they demonstrated the reliability of thrust and sliding equilibrium method used to analyze the stability of embankment.
This experiment was based on the embankment of the highway from Changde to Zhangjiajie,which used shale and limestone in its two sections separately.The shear strength indexes of ? and c were obtained for these two embankments,and they demonstrated the reliability of thrust and sliding equilibrium method used to analyze the stability of embankment.
Abstract：
The superstructure analyzed by three-dimensional substructure method was divided into some substructures and the stiffness matrix be condensed from top to bottom.The boundary element method and the finite element method were applied to analyze the raft foundation on Winkler elastic foundation.The coupling equation was obtained by using both the equilibrium of force and the coordination of displacement.An engineering example was given to illustrate the method,and the results showed that efficiency and accuracy of the present method were higher than those of other methods.
The superstructure analyzed by three-dimensional substructure method was divided into some substructures and the stiffness matrix be condensed from top to bottom.The boundary element method and the finite element method were applied to analyze the raft foundation on Winkler elastic foundation.The coupling equation was obtained by using both the equilibrium of force and the coordination of displacement.An engineering example was given to illustrate the method,and the results showed that efficiency and accuracy of the present method were higher than those of other methods.
Abstract：
In order to get reliable construction parameters and design parameters of Suzhou-Nantong Yangtze River Bridge,4 tests of piles were taken,including 7 piles with grouting.According to the results of self-balanced static load tests,not only base resistances were improved after grouting,but also frictional resistances were improved by bettering the characteristics of soils and interfaces between piles and soils.After grouting,the frictional resistances were increased by 12.39%～52.87%,and the base resistances were increased by 1.46～6.21 times.The ratios of frictional resistance increment in the ultimate bearing capacity increment were 56%～88%.
In order to get reliable construction parameters and design parameters of Suzhou-Nantong Yangtze River Bridge,4 tests of piles were taken,including 7 piles with grouting.According to the results of self-balanced static load tests,not only base resistances were improved after grouting,but also frictional resistances were improved by bettering the characteristics of soils and interfaces between piles and soils.After grouting,the frictional resistances were increased by 12.39%～52.87%,and the base resistances were increased by 1.46～6.21 times.The ratios of frictional resistance increment in the ultimate bearing capacity increment were 56%～88%.
2006, 28(1): 118-122.
Abstract：
Where as some scholars commented on the generalized plastic mechanics(GPM) and put forward their doubts and opinions,some further interpretations of GPM were presented and its origin and essential ideas were expatiated clearly.The isotropic hardening model,which was commonly adopted in classical plastic mechanics and GPM,and the physical meaning of yield surface were analyzed deeply.Some problems,such as rate-independent plasticity,Drucker postulate,sign of plastic coefficient,convexity and uniqueness of yield surface and so on,were answered and discussed.
Where as some scholars commented on the generalized plastic mechanics(GPM) and put forward their doubts and opinions,some further interpretations of GPM were presented and its origin and essential ideas were expatiated clearly.The isotropic hardening model,which was commonly adopted in classical plastic mechanics and GPM,and the physical meaning of yield surface were analyzed deeply.Some problems,such as rate-independent plasticity,Drucker postulate,sign of plastic coefficient,convexity and uniqueness of yield surface and so on,were answered and discussed.
