The simulation of large-strain geotechnical laboratory tests with conventional Lagrangian finite element method(FEM)techniques is often problematic due to excessive mesh distortion.The multiple reversal direct shear(M...The simulation of large-strain geotechnical laboratory tests with conventional Lagrangian finite element method(FEM)techniques is often problematic due to excessive mesh distortion.The multiple reversal direct shear(MRDS)test can be used to measure the residual shear strength of soils in a laboratory setting.However,modelling and simulation generally require advanced numerical methods to accommodate the large shear strains concentrated in the shear plane.In reality,when the standard direct shear(DS)apparatus is used,the MRDS method is prone to two major sources of measurement error:load cap tilting and specimen loss.These sources of error make it difficult or even impossible to correctly determine the residual shear strength.This paper presents a modified DS apparatus and multi-reversal multi-stage test method,simulated using the coupled Eulerian-Lagrangian(CEL)method in a finite element environment.The method was successful in evaluating equipment and preventing both load cap tilting and specimen loss,while modelling large-deformation behaviour that is not readily simulated with the conventional FEM or arbitrary Lagrangian-Eulerian(ALE)analysis.Thereafter,a modified DS apparatus was created for the purpose of analysing mixtures of organic materials found in an Australian clay.The results obtained from the modified DS CEL model in combination with laboratory tests show a great improvement in the measured residual shear strength profiles compared to those from the standard apparatus.The modified DS setup ensures that accurate material residual shear strengths are calculated,a factor that is vital to ensure appropriate soil behaviour is simulated for numerical analyses of large-scale geotechnical projects.展开更多
An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel.However,due to the complex interaction between the failed tunnel structure and the soil medi...An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel.However,due to the complex interaction between the failed tunnel structure and the soil medium,the mechanism by which the failure is propagated between two closely spaced tunnels remains unclear.In this study,the coupled EulerianLagrangian(CEL)modelling technique was adopted to investigate the influence of a failed tunnel(FT)on an adjacent tunnel,which was termed an“influenced tunnel”(IT).The safety of the IT was analysed in detail under different circumstances,such as different failure positions of the FT,different failure degrees of the FT,and different spatial relationships between the two tunnels.The simulation results indicated that the most adverse case may occur when the two tunnels are arranged as offsets and the IT is the upper tunnel.Under this circumstance,significant shear deformation may occur in IT because IT is located at the shear band of the FT.展开更多
文摘The simulation of large-strain geotechnical laboratory tests with conventional Lagrangian finite element method(FEM)techniques is often problematic due to excessive mesh distortion.The multiple reversal direct shear(MRDS)test can be used to measure the residual shear strength of soils in a laboratory setting.However,modelling and simulation generally require advanced numerical methods to accommodate the large shear strains concentrated in the shear plane.In reality,when the standard direct shear(DS)apparatus is used,the MRDS method is prone to two major sources of measurement error:load cap tilting and specimen loss.These sources of error make it difficult or even impossible to correctly determine the residual shear strength.This paper presents a modified DS apparatus and multi-reversal multi-stage test method,simulated using the coupled Eulerian-Lagrangian(CEL)method in a finite element environment.The method was successful in evaluating equipment and preventing both load cap tilting and specimen loss,while modelling large-deformation behaviour that is not readily simulated with the conventional FEM or arbitrary Lagrangian-Eulerian(ALE)analysis.Thereafter,a modified DS apparatus was created for the purpose of analysing mixtures of organic materials found in an Australian clay.The results obtained from the modified DS CEL model in combination with laboratory tests show a great improvement in the measured residual shear strength profiles compared to those from the standard apparatus.The modified DS setup ensures that accurate material residual shear strengths are calculated,a factor that is vital to ensure appropriate soil behaviour is simulated for numerical analyses of large-scale geotechnical projects.
基金the National Natural Science Foundation of China(Nos.41630641 and 51808387)。
文摘An increasing number of engineering accidents have shown that the failure of a tunnel can propagate to a neighbouring tunnel.However,due to the complex interaction between the failed tunnel structure and the soil medium,the mechanism by which the failure is propagated between two closely spaced tunnels remains unclear.In this study,the coupled EulerianLagrangian(CEL)modelling technique was adopted to investigate the influence of a failed tunnel(FT)on an adjacent tunnel,which was termed an“influenced tunnel”(IT).The safety of the IT was analysed in detail under different circumstances,such as different failure positions of the FT,different failure degrees of the FT,and different spatial relationships between the two tunnels.The simulation results indicated that the most adverse case may occur when the two tunnels are arranged as offsets and the IT is the upper tunnel.Under this circumstance,significant shear deformation may occur in IT because IT is located at the shear band of the FT.
