1999 Vol. 21 No. 2
Abstract：
Differences between the recently developed method and the conventional method of estimating the water and earth pressures on the supporting structure around a foundation pit are described The conditions of application and limitations of these two methods are clarified based on the analysis of change of pore pressure,effective stress and shear strength of soil adjacent to the supporting structure
Differences between the recently developed method and the conventional method of estimating the water and earth pressures on the supporting structure around a foundation pit are described The conditions of application and limitations of these two methods are clarified based on the analysis of change of pore pressure,effective stress and shear strength of soil adjacent to the supporting structure
Abstract：
A calculating method for optimizing of the cross sectional shape of a subterranean tunnel and its application have been studied in this paper. The characteristic dimension of cross section of the tunnel has been taken as the design variable, while the total failure area within adjoining rock as the objective function and the area of water carrying section required as the restraint condition. The non linear optimization problem with constraint has been solved by use of the sequential unconstrained minimization technique (SUMT). The cross section of tunnel of a proposed project has been optimized and analyzed. And the result obtained is reasonable.
A calculating method for optimizing of the cross sectional shape of a subterranean tunnel and its application have been studied in this paper. The characteristic dimension of cross section of the tunnel has been taken as the design variable, while the total failure area within adjoining rock as the objective function and the area of water carrying section required as the restraint condition. The non linear optimization problem with constraint has been solved by use of the sequential unconstrained minimization technique (SUMT). The cross section of tunnel of a proposed project has been optimized and analyzed. And the result obtained is reasonable.
Abstract：
Four point bending samples are used to determine the criteria of compound fracture for frozen soil. Details of preparation of samples and criteria of fracture are given. Furthermore, test results and conclusion are discussed and some advice is given.
Four point bending samples are used to determine the criteria of compound fracture for frozen soil. Details of preparation of samples and criteria of fracture are given. Furthermore, test results and conclusion are discussed and some advice is given.
Abstract：
In this paper,through establishing model of back analysis,the modulus of deformation for foundation after dynamic consolidation can be determined by single valued back analysis method, in which the settlement modulus of deformation curve and the final drop settlement for control of soil densification are used.Based on the basic theory of plate loading test,the allowable bearing capacity can be predicted by the relative settlement ratio method. Many practical examples of calculation show that the calculated results can satisfy the engineering demand and have high reliability.Therefore,a new method is provided to predict the improvement effect, to check the rationality of orignal design and to improve the design for dynamic consolidation.
In this paper,through establishing model of back analysis,the modulus of deformation for foundation after dynamic consolidation can be determined by single valued back analysis method, in which the settlement modulus of deformation curve and the final drop settlement for control of soil densification are used.Based on the basic theory of plate loading test,the allowable bearing capacity can be predicted by the relative settlement ratio method. Many practical examples of calculation show that the calculated results can satisfy the engineering demand and have high reliability.Therefore,a new method is provided to predict the improvement effect, to check the rationality of orignal design and to improve the design for dynamic consolidation.
Abstract：
Results obtained from laboratory tests of lime silt under frost and thaw cycles show that the shear strengths of lime silt and silt do not change with confining pressure. For saturated and unsaturated lime silt, their strength values are all higher than that of silt and the greater the dry unit weight is, the higher the shear strength is. The shear strength of unsaturated lime silt is greater than that of the saturated lime silt. After 1 frost and thaw cycle, the shear strength of silt has a little change, but the shear strength of lime silt is obviously lower than that of lime silt before frost and thaw cycle. After many cycles of frost and thaw, the shear strength of lime silt gradually decreases with increasing cycles of frost and thaw, and after 10 cycles, it reaches to a minimum value.
Results obtained from laboratory tests of lime silt under frost and thaw cycles show that the shear strengths of lime silt and silt do not change with confining pressure. For saturated and unsaturated lime silt, their strength values are all higher than that of silt and the greater the dry unit weight is, the higher the shear strength is. The shear strength of unsaturated lime silt is greater than that of the saturated lime silt. After 1 frost and thaw cycle, the shear strength of silt has a little change, but the shear strength of lime silt is obviously lower than that of lime silt before frost and thaw cycle. After many cycles of frost and thaw, the shear strength of lime silt gradually decreases with increasing cycles of frost and thaw, and after 10 cycles, it reaches to a minimum value.
Abstract：
This paper proposed the concept of deformation control design for retaining structure in deep excavation, and dealt with the basic content and design principle. Based on the theory of engineering control, the formula describing the process of deformation control design has been put forword. At last, the application of deformation control design has been shown by a practical project.
This paper proposed the concept of deformation control design for retaining structure in deep excavation, and dealt with the basic content and design principle. Based on the theory of engineering control, the formula describing the process of deformation control design has been put forword. At last, the application of deformation control design has been shown by a practical project.
Abstract：
A rheological model was presented for describing a time dependent behavior of excavated highslope of rock mass. This model is implemented in a finite element program. As an actual example, the rheological behavior for highslope of shiplock in Three Gorges Project was studied and the numerical results were compared with instantaneous response data of elasto plastic analysis.
A rheological model was presented for describing a time dependent behavior of excavated highslope of rock mass. This model is implemented in a finite element program. As an actual example, the rheological behavior for highslope of shiplock in Three Gorges Project was studied and the numerical results were compared with instantaneous response data of elasto plastic analysis.
Abstract：
ln this paper,based on engineering geological exploration and static or dynamic triaxial test, the structure,seismic and liquefaction resistance of tailing dams were studied. The results show that the structure of dams was improved, and seismic and liquefaction resistance were strengthened remarkably by using the new technique.
ln this paper,based on engineering geological exploration and static or dynamic triaxial test, the structure,seismic and liquefaction resistance of tailing dams were studied. The results show that the structure of dams was improved, and seismic and liquefaction resistance were strengthened remarkably by using the new technique.
1999, 21(2): 42-48.
Abstract：
The dilatometer test (DMT) is a very useful in situ testing method. Based on data analysis of several DMT tests in Shanghai, a proper formula was obtained in this paper for local application through combining the local soil characteristics and foreign experience. With this formula, a set of soil parameters from DMT indices could be inferred for foundation design, compaction control, liquefaction estimation, and so on.
The dilatometer test (DMT) is a very useful in situ testing method. Based on data analysis of several DMT tests in Shanghai, a proper formula was obtained in this paper for local application through combining the local soil characteristics and foreign experience. With this formula, a set of soil parameters from DMT indices could be inferred for foundation design, compaction control, liquefaction estimation, and so on.
1999, 21(2): 49-53.
Abstract：
The problem of critical length of pile in composite foundation is studied by means of FEM analysis in which the loads are exerted separately on a single flexible pile,large area of flexible piles group and flexible piles group under road embankment.The conclusion is reached that the critical length of pile in composite foundation is related not only to the modular ratio of pile /soil but also to the load distribution.
The problem of critical length of pile in composite foundation is studied by means of FEM analysis in which the loads are exerted separately on a single flexible pile,large area of flexible piles group and flexible piles group under road embankment.The conclusion is reached that the critical length of pile in composite foundation is related not only to the modular ratio of pile /soil but also to the load distribution.
Abstract：
For the subject on drainage consolidation method of combining static and dynamic loading, the reconsolidation characteristics of saturated soft clay under impact loading are studied by laboratory tests , and particularly, the influence of drainage condition on consolidation and reconsolidation of soft clay are analysed. Based on test results, the uniqueness of the relationship between pore pressure and reconsolidation volumetric strain is pointed out . The methods for determining coefficient of reconsolidation volume compressibility and reconsolidation index are given. Finally, a model for predicting the settlement of soft clay foundation after impact loading is suggested, which fits well with test results.
For the subject on drainage consolidation method of combining static and dynamic loading, the reconsolidation characteristics of saturated soft clay under impact loading are studied by laboratory tests , and particularly, the influence of drainage condition on consolidation and reconsolidation of soft clay are analysed. Based on test results, the uniqueness of the relationship between pore pressure and reconsolidation volumetric strain is pointed out . The methods for determining coefficient of reconsolidation volume compressibility and reconsolidation index are given. Finally, a model for predicting the settlement of soft clay foundation after impact loading is suggested, which fits well with test results.
1999, 21(2): 61-64.
Abstract：
This paper has described the creep tests of six different kinds of soil and crushed stone mixture, including the preparation of samples, collection of data, and interpretation of results. The creep curves were obtained by using regression and iteration analysis method, which make it possible to calculate the settlement after construction of high fill with visco elastic parameters.
This paper has described the creep tests of six different kinds of soil and crushed stone mixture, including the preparation of samples, collection of data, and interpretation of results. The creep curves were obtained by using regression and iteration analysis method, which make it possible to calculate the settlement after construction of high fill with visco elastic parameters.
Abstract：
This paper presents a practical method to evaluate the longitudinal elasto plastic stiffness of shield tunnel,and proposes a calculation procedure to estimate the seismic stress caused by the seismic ground displacement and earthquake induced settlement.As an numerical example,the procedure is applied to analyze the seismic stress of the Shanghai Yanan East Road tunnels across the Huangpu River.
This paper presents a practical method to evaluate the longitudinal elasto plastic stiffness of shield tunnel,and proposes a calculation procedure to estimate the seismic stress caused by the seismic ground displacement and earthquake induced settlement.As an numerical example,the procedure is applied to analyze the seismic stress of the Shanghai Yanan East Road tunnels across the Huangpu River.
Abstract：
The article states the influence of comprehensive stress (difference between verticle stress and side constraint) and verticle strain on the deformation modulus of pile in composite foundation . It is pointed out that the side constraint imposed by soil around the pile depends on the soil type and its state of stress. Based on the interaction between pile and soil, analyses are made on three different kinds of loading test on composite foundation composed of pile group, composite foundation composed of single pile and single pile respectively. The computation formula for the deformation modulus of pile is established accordingly.
The article states the influence of comprehensive stress (difference between verticle stress and side constraint) and verticle strain on the deformation modulus of pile in composite foundation . It is pointed out that the side constraint imposed by soil around the pile depends on the soil type and its state of stress. Based on the interaction between pile and soil, analyses are made on three different kinds of loading test on composite foundation composed of pile group, composite foundation composed of single pile and single pile respectively. The computation formula for the deformation modulus of pile is established accordingly.
Abstract：
Base on the displacement back analysis and in accordance with the special characteristics of structural planes in rock masses, the weighted displacement back analysis is introduced to determine the parameters of possible stable control planes using in site measured displacements. Then the validity of weighted displacement back analysis is proved through sensitivity analysis. As an example, the parameters c,f of some siltized intercalation in a rock slope of a practical project are obtained by the use of this method. The results show that this method has high practical value.
Base on the displacement back analysis and in accordance with the special characteristics of structural planes in rock masses, the weighted displacement back analysis is introduced to determine the parameters of possible stable control planes using in site measured displacements. Then the validity of weighted displacement back analysis is proved through sensitivity analysis. As an example, the parameters c,f of some siltized intercalation in a rock slope of a practical project are obtained by the use of this method. The results show that this method has high practical value.
Abstract：
The identifiability of visco plastic flow coefficient γ was discussed. Then, the method of back analysis to identify the flow coefficient γ was proposed, and an appropriate calculating program was compiled. It was confirmed that the method is feasible through a practical example.
The identifiability of visco plastic flow coefficient γ was discussed. Then, the method of back analysis to identify the flow coefficient γ was proposed, and an appropriate calculating program was compiled. It was confirmed that the method is feasible through a practical example.
1999, 21(2): 82-86.
Abstract：
Systematic tests are made for the geogrid reinforced stone. The results show that the stress strain condition of geogrid reinforced body, distance of geogrid interlayer and stone properties are of important factors of reinforcement. The stone strength is obviously increased and its deformation is decreased by reinforcement. Mechanism of geogrid reinforced stone is in accord with pseudo cohesion concept. Tensiomembrane reaction is effective only under some special conditions.
Systematic tests are made for the geogrid reinforced stone. The results show that the stress strain condition of geogrid reinforced body, distance of geogrid interlayer and stone properties are of important factors of reinforcement. The stone strength is obviously increased and its deformation is decreased by reinforcement. Mechanism of geogrid reinforced stone is in accord with pseudo cohesion concept. Tensiomembrane reaction is effective only under some special conditions.
Abstract：
In this paper, based on the measured reinforcement stresses in the retaining piles for the deep excavation in Chengdu Jinyang Trade Mansion, the corresponding bending moments in the piles are found Then the deformation condition of the retaining piles is examined It is indicated that the ring beam on top of the piles has appreciable restriction effect which prevent the tops of the piles from displacing and rotating freely So the behavior of the retaining piles under lateral pressure is quite different from that of the upright free head shaft Taking the moments found from the reinforcement stresses as the measured values, and the moments computed by considering the top restraint forces as the calculated values, the distribution and value of the earth pressure above the excavation surface on the retaining piles are back analyzed by means of the method of least squares The results are quite different from those obtained by the classical Coulomb′s or Rankine′s earth pressure theory
In this paper, based on the measured reinforcement stresses in the retaining piles for the deep excavation in Chengdu Jinyang Trade Mansion, the corresponding bending moments in the piles are found Then the deformation condition of the retaining piles is examined It is indicated that the ring beam on top of the piles has appreciable restriction effect which prevent the tops of the piles from displacing and rotating freely So the behavior of the retaining piles under lateral pressure is quite different from that of the upright free head shaft Taking the moments found from the reinforcement stresses as the measured values, and the moments computed by considering the top restraint forces as the calculated values, the distribution and value of the earth pressure above the excavation surface on the retaining piles are back analyzed by means of the method of least squares The results are quite different from those obtained by the classical Coulomb′s or Rankine′s earth pressure theory
Abstract：
This paper has deduced typical stability factor of rock slope under the action of groundwater. Figures that express relationship of stability factor against overturning and geometric factor as well as critical curve for overturning were drawn. Stability factor against overturning can be directly obtained from these figures.
This paper has deduced typical stability factor of rock slope under the action of groundwater. Figures that express relationship of stability factor against overturning and geometric factor as well as critical curve for overturning were drawn. Stability factor against overturning can be directly obtained from these figures.
1999, 21(2): 95-100.
Abstract：
Steady state strength is an important parameter in evaluating the stability of sand deposits against flow liquefaction. Most loose sands exhibit the quasi steady state (QSS) behavior under undrained triaxial loading, in which no unique ultimate steady state is reached. Stress controlled triaxial tests were carried out on Unimin sand to study the steady state strength in the QSS behavior. The test results indicate that there are usually four distinct deformation stages in undrained tests on loose sand: initial stage, collapse stage, critical stress stage and post failure stage. The strain rate approximately remains constant in each deformation stage. The steady state, in which pore pressure, deviator stress, effective stress and strain rate remain constant, occurs in the collapse stage. The conventional definition of the steady state of deformation is not completely valid for the QSS behavior, and a modified definition is suggested.
Steady state strength is an important parameter in evaluating the stability of sand deposits against flow liquefaction. Most loose sands exhibit the quasi steady state (QSS) behavior under undrained triaxial loading, in which no unique ultimate steady state is reached. Stress controlled triaxial tests were carried out on Unimin sand to study the steady state strength in the QSS behavior. The test results indicate that there are usually four distinct deformation stages in undrained tests on loose sand: initial stage, collapse stage, critical stress stage and post failure stage. The strain rate approximately remains constant in each deformation stage. The steady state, in which pore pressure, deviator stress, effective stress and strain rate remain constant, occurs in the collapse stage. The conventional definition of the steady state of deformation is not completely valid for the QSS behavior, and a modified definition is suggested.
