In this study,an iterative-based three-dimensional finite element lower bound in association with the second-order cone programming method is adopted to evaluate the limit load of a single pile embedded in cross-aniso...In this study,an iterative-based three-dimensional finite element lower bound in association with the second-order cone programming method is adopted to evaluate the limit load of a single pile embedded in cross-anisotropic soils under general loading condition.The lower bound solutions of the pile embedded in an anisotropic soil deposit can be found by formulating the element equilibrium,equilibrium of shear and normal stresses along discontinuities,boundary conditions,yield function,and optimizing the objective function through the second-order cone programming method in conjunction with an iterative-based update procedure.A general loading condition is considered to profile the expansion of the safe load in the vertical-horizontal-moment(V-H-M)space.The results of this study are compared and validated against three different cases including an isotropic lateral loading,anisotropic end bearing capacity,and a pile embedded in an isotropic soil deposit under general loading condition.A parametric study is conducted to evaluate the impact of different influencing factors.It was found that the effect of anisotropy on the variation of lateral limit load of a single pile is more pronounced than the corresponding vertical and bending moment limit loads,whereas the interface properties have more significant effects on the vertical and bending moment limit loads in comparison to the lateral limit load.展开更多
An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompress...An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompressible solid grain. Using Fourier-Bessel series, the problem of multiple scattering is solved by imposing continuity conditions and equilibrium conditions at the soil-pile interfaces with the translational addition theorem. A parametric analysis is conducted to investigate the influence of the permeability of poroelastic soil, separation between piles, number of piles and frequency of incident waves on screening effectiveness of the barrier, and the results are compared with those in an elastic soil medium. Computed results show that the intrinsic permeability of the soil medium displays an apparent effect on the screening of plane S waves.展开更多
Piled embankments have been extensively used for high-speed rail over soft soils because of their effectiveness in minimizing differential settlement and shortening the construction period.Stress concentration ratio,d...Piled embankments have been extensively used for high-speed rail over soft soils because of their effectiveness in minimizing differential settlement and shortening the construction period.Stress concentration ratio,defined as the ratio of vertical stress carried by pile heads(or pile caps if applicable)to that by adjacent soils,is a fundamental parameter in the design of piled embankments.In view of the complicated load transfer mechanism in the framework of embankment system,this paper presents a simplified analytical solution for the stress concentration ratio of rigid pile-supported embankments.In the derivation,the effects of cushion stiffness,pile–soil interaction,and pile penetration behavior are considered and examined.A modified linearly elastic-perfectly plastic model was used to analyze the mechanical response of a rigid pile–soil system.The analytical model was verified against field data and the results of numerical simulations from the literature.According to the proposed method,the skin friction distribution,pile–soil relative displacement,location of neural point,and differential settlement between the pile head(or cap)and adjacent soils can be determined.This work serves as a fast algorithm for initial and reasonable approximation of stress concentration ratio on the design aspects of piled embankments.展开更多
文摘In this study,an iterative-based three-dimensional finite element lower bound in association with the second-order cone programming method is adopted to evaluate the limit load of a single pile embedded in cross-anisotropic soils under general loading condition.The lower bound solutions of the pile embedded in an anisotropic soil deposit can be found by formulating the element equilibrium,equilibrium of shear and normal stresses along discontinuities,boundary conditions,yield function,and optimizing the objective function through the second-order cone programming method in conjunction with an iterative-based update procedure.A general loading condition is considered to profile the expansion of the safe load in the vertical-horizontal-moment(V-H-M)space.The results of this study are compared and validated against three different cases including an isotropic lateral loading,anisotropic end bearing capacity,and a pile embedded in an isotropic soil deposit under general loading condition.A parametric study is conducted to evaluate the impact of different influencing factors.It was found that the effect of anisotropy on the variation of lateral limit load of a single pile is more pronounced than the corresponding vertical and bending moment limit loads,whereas the interface properties have more significant effects on the vertical and bending moment limit loads in comparison to the lateral limit load.
基金Project (No. 50778136) supported by the National Natural Science Foundation of China
文摘An array of rigid piles used as a screening barrier for plane shear (S) waves is investigated in a homogeneous unbounded space. The dynamic poroelastic theory of Biot is employed, under the assumption of an incompressible solid grain. Using Fourier-Bessel series, the problem of multiple scattering is solved by imposing continuity conditions and equilibrium conditions at the soil-pile interfaces with the translational addition theorem. A parametric analysis is conducted to investigate the influence of the permeability of poroelastic soil, separation between piles, number of piles and frequency of incident waves on screening effectiveness of the barrier, and the results are compared with those in an elastic soil medium. Computed results show that the intrinsic permeability of the soil medium displays an apparent effect on the screening of plane S waves.
基金supported by the National Natural Science Foundation of China(Grant Nos.52078435 and 41901073)Shanghai Key Laboratory of Rail Infrastructure Durability and System Safety(Grant No.R202003)China Postdoctoral Science Foundation(Grant No.2019M663556).
文摘Piled embankments have been extensively used for high-speed rail over soft soils because of their effectiveness in minimizing differential settlement and shortening the construction period.Stress concentration ratio,defined as the ratio of vertical stress carried by pile heads(or pile caps if applicable)to that by adjacent soils,is a fundamental parameter in the design of piled embankments.In view of the complicated load transfer mechanism in the framework of embankment system,this paper presents a simplified analytical solution for the stress concentration ratio of rigid pile-supported embankments.In the derivation,the effects of cushion stiffness,pile–soil interaction,and pile penetration behavior are considered and examined.A modified linearly elastic-perfectly plastic model was used to analyze the mechanical response of a rigid pile–soil system.The analytical model was verified against field data and the results of numerical simulations from the literature.According to the proposed method,the skin friction distribution,pile–soil relative displacement,location of neural point,and differential settlement between the pile head(or cap)and adjacent soils can be determined.This work serves as a fast algorithm for initial and reasonable approximation of stress concentration ratio on the design aspects of piled embankments.