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
A novel modeling technique based on the coupled Eulerian-Lagrangian(CEL) method is provided to solve the geotechnical problems with large deformations. The technique is intended to solve the update problem of soil mec...A novel modeling technique based on the coupled Eulerian-Lagrangian(CEL) method is provided to solve the geotechnical problems with large deformations. The technique is intended to solve the update problem of soil mechanical properties during spudcan penetration in normally consolidated clay soil. In the CEL model, the normal method of assigning an increasing shear strength profile with depth(NA) is defective due to its Eulerian framework. In this paper, a new technique is proposed to update soil material properties by introducing thermo-mechanical coupled analysis(TMCA) to the CEL models. During establishment of the CEL models, the optimal penetration velocity and minimum mesh size are determined through parametric studies. Reasonability and accuracy are then verified through comparison of the preliminary results with the soil flow configuration and penetration resistance(Fv) of a centrifuge test, and the results of the proposed method are compared with those of the remeshing and interpolation technique with small strain(RITSS) method. To achieve a CEL model with satisfactory accuracy, the NA and TMCA methods implemented in the CEL models and the RITSS method are first adopted in weightless soil. Comparison of the findings with those obtained in previous studies shows that the TMCA method can update material properties and predict Fv. The TMCA method is then applied to soils with self-weight and different shear strength profiles. Results show that the proposed method is capable of accurately modeling the large deformation problem of spudcan penetration in non-homogeneous clay.展开更多
针对海上设施的安全防护问题,提出了一种网-桁架式海上拦截装置,目的是在有效拦截来袭小艇撞击的同时尽量降低对拦截装置本身的损伤.为验证这一装置的有效性,基于显式动力学和欧拉-拉格朗日耦合方法对拦截装置拦截小艇过程进行数值模拟...针对海上设施的安全防护问题,提出了一种网-桁架式海上拦截装置,目的是在有效拦截来袭小艇撞击的同时尽量降低对拦截装置本身的损伤.为验证这一装置的有效性,基于显式动力学和欧拉-拉格朗日耦合方法对拦截装置拦截小艇过程进行数值模拟,设定小艇垂直撞击支撑柱、支撑柱间隙和45°撞击支撑柱、支撑柱间隙4种工况,每种工况包含10、20、30 m/s 3种速度.通过对这12组仿真的碰撞力、能量以及破损状态分析,全方位分析了该装置的防撞性能和对小艇的拦截效果.所有工况下该装置都能完成对小艇的拦截,说明这种装置具有优秀的拦截效果.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supported by the National Natural Science Foundation of China (No. 51779236)the NSFC-Shandong Joint Fund Project (No. U1706226)funded by the China Scholarship Council (No. 201606330049)
文摘A novel modeling technique based on the coupled Eulerian-Lagrangian(CEL) method is provided to solve the geotechnical problems with large deformations. The technique is intended to solve the update problem of soil mechanical properties during spudcan penetration in normally consolidated clay soil. In the CEL model, the normal method of assigning an increasing shear strength profile with depth(NA) is defective due to its Eulerian framework. In this paper, a new technique is proposed to update soil material properties by introducing thermo-mechanical coupled analysis(TMCA) to the CEL models. During establishment of the CEL models, the optimal penetration velocity and minimum mesh size are determined through parametric studies. Reasonability and accuracy are then verified through comparison of the preliminary results with the soil flow configuration and penetration resistance(Fv) of a centrifuge test, and the results of the proposed method are compared with those of the remeshing and interpolation technique with small strain(RITSS) method. To achieve a CEL model with satisfactory accuracy, the NA and TMCA methods implemented in the CEL models and the RITSS method are first adopted in weightless soil. Comparison of the findings with those obtained in previous studies shows that the TMCA method can update material properties and predict Fv. The TMCA method is then applied to soils with self-weight and different shear strength profiles. Results show that the proposed method is capable of accurately modeling the large deformation problem of spudcan penetration in non-homogeneous clay.
文摘针对海上设施的安全防护问题,提出了一种网-桁架式海上拦截装置,目的是在有效拦截来袭小艇撞击的同时尽量降低对拦截装置本身的损伤.为验证这一装置的有效性,基于显式动力学和欧拉-拉格朗日耦合方法对拦截装置拦截小艇过程进行数值模拟,设定小艇垂直撞击支撑柱、支撑柱间隙和45°撞击支撑柱、支撑柱间隙4种工况,每种工况包含10、20、30 m/s 3种速度.通过对这12组仿真的碰撞力、能量以及破损状态分析,全方位分析了该装置的防撞性能和对小艇的拦截效果.所有工况下该装置都能完成对小艇的拦截,说明这种装置具有优秀的拦截效果.
