ABSTRACT

Smoothed particle hydrodynamics (SPH) has been applied to simulate failure process of a soil sample under unconfined compression loading conditions. The elastic-plastic constitutive model of geomaterial is developed based on Drucker-Prager yield criterion, considering (i) associative (ii) non-associative plastic flow rules. Velocity boundary conditions of the upper and lower platens are applied in the model. This paper composes the results in terms of von Mises stress and accumulation of effective plastic strain in the sample for both associative and non-associative conditions.

INTRODUCTION

Prediction of failure of geomaterial is a major concern in various excavations made in soil or rock viz. tunnels, slopes and mining excavations. Failure of geomaterial is characterized by the initiation, propagation and interaction of several cracks, defects and inherent flaws. The modelling of failure behavior due to large deformation is very difficult by using grid based numerical method because of severe grid distortion and hence degrades the accuracy and increases the complexity in the implementation. The study of failure behavior depends a great extent on small scale laboratory experimental results and some empirical relations. Predictions of the failure process using numerical simulations can contribute a useful knowledge in engineering practices and design. Recently, active development of meshfree methods provide a platform to simulate failure process without spatial discretize mesh. In this paper, Lagrangian meshfree particle method, namely smoothed particle hydrodynamics (SPH) has been used to simulate the failure of soil sample under uniaxial compressive loading. SPH is gridless Lagrangian particle method which replaces the continuum equations of fluid by particle equation.

Each particle has fixed mass, which follows the kinematic of fluid motion, advecting contact discontinuity, preserving Galilean invariance and reducing the computational diffusion of various fluid particles including momentum. It is often possible to formulate SPH in such a way that mass, momentum and energy are conserved exactly. SPH was originally developed for astrophysical applications. It is relatively easy to incorporate complicated physical effects into the SPH formalism and thus SPH has been applied successfully to a various type of problems such as elastic dynamics, dynamic response of material strength, fluid-structure interaction and other applications. Bui et al. implemented SPH that solve plastic soil behavior for slope failure, landslides, bearing capacity. Benz and Asphaug first extended SPH to the simulation of the fracture of brittle solid. Recently, Das and Cleary simulated brittle fracture of rock using Grady-Kipp damage model. This paper explores the potential of SPH to predict the failure behavior of geomaterial under static loading conditions and examines the von Mises stress and effective plastic strain distribution in the whole domain. The Drucker-Prager model with associative and non-associative plastic flow rule has been employed to study elastic-plastic nature of the material. The capability of the model is demonstrated through the simulations of an Unconfined Compression Strength (UCS) test of Drucker-Prager soil.

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