Evaluation of Shear Modulus and Damping Ratio of Granular Materials Using Discrete Element Approach

In this paper, an attempt has been made to highlight the influence of different parameters such as number of cycles, confining pressure, void ratio, gradation, initial anisotropy and stress path on the dynamic properties of granular materials using Discrete Element Method (DEM). A series of strain controlled cyclic triaxial numerical simulations using three dimensional DEM have been carried out on an assembly of spheres. Dynamic properties such shear modulus (G) and damping ratio (D) were determined from the typical hysteresis loop obtained during cyclic triaxial test simulation. It has been observed from the test results that the numerical simulation using DEM has captured the variation of dynamic properties over a wide range of shear strain values for different parameters considered for the current investigation. Maximum shear modulus (Gmax) was found to be influenced by initial confining pressure, void ratio, gradation and initial anisotropy. Whereas, the damping ratio (D) was found to be influenced by number of cycles, initial confining pressure, gradation and stress path. Further it has been shown that the variation of shear modulus with shear strain can be divided into three distinct zones such as Isotropic Zone (IZ), Anisotropic Zone (AZ) and Stable Anisotropic Zone (SAZ). A drastic reduction of shear modulus with shear strain has been observed in the Anisotropic Zone (AZ). In addition, the results obtained using numerical simulations have been compared with the laboratory experimental values.

[1]  V. Drnevich,et al.  Shear Modulus and Damping in Soils: Measurement and Parameter Effects (Terzaghi Leture) , 1972 .

[2]  T. G. Sitharam,et al.  Discrete element modelling of cyclic behaviour of granular materials , 2003 .

[3]  Fumio Tatsuoka,et al.  Hysteretic Damping of Sands under Cyclic Loading and its Relation to Shear Modulus , 1978 .

[4]  Braja M. Das,et al.  Principles of Soil Dynamics , 1992 .

[5]  Fumio Tatsuoka,et al.  EFFECTS OF GRAIN SIZE AND GRADING ON DYNAMIC SHEAR MODULI OF SANDS , 1977 .

[6]  Takeji Kokusho,et al.  CYCLIC TRIAXIAL TEST OF DYNAMIC SOIL PROPERTIES FOR WIDE STRAIN RANGE , 1980 .

[7]  T. G. Sitharam,et al.  Micromechanical modelling of monotonic drained and undrained shear behaviour of granular media using three‐dimensional DEM , 2002 .

[8]  K. Ishihara,et al.  Soil Behaviour In Earthquake Geotechnics , 1996 .

[9]  Micro-mechanical analysis and modelling of granular materials loaded at constant volume , 1998 .

[10]  Ricardo Dobry,et al.  NUMERICAL SIMULATIONS OF MONOTONIC AND CYCLIC LOADING OF GRANULAR SOIL , 1994 .

[11]  R. Bathurst,et al.  Analytical study of induced anisotropy in idealized granular materials , 1989 .

[12]  T. Sitharam,et al.  Critical state behaviour of granular materials from isotropic and rebounded paths: DEM simulations , 2009 .

[13]  H. Seed.  Soil moduli and damping factors for dynamic response analyses , 1970 .

[14]  H B Seed,et al.  VOLUME CHANGES IN SANDS DURING CYCLIC LOADING , 1971 .

[15]  P. Cundall,et al.  A discrete numerical model for granular assemblies , 1979 .

[16]  V. Drnevich,et al.  Evaluation of Dynamic Properties of Sands by Resonant Column Testing , 1984 .

[17]  L K Chien,et al.  Influence of fines content and initial shear stress on dynamic properties of hydraulic reclaimed soil , 2002 .

[18]  Fumio Tatsuoka,et al.  SHEAR MODULUS AND DAMPING BY DRAINED TESTS ON CLEAN SAND SPECIMENS RECONSTITUTED BY VARIOUS METHODS , 1979 .