ABSTRACT:

Shear failure mode and strength of artificial rock joints are studied under different levels of joint compression. A quasi-static discrete element modeling is presented that reproduces the brittle material as a dense assemblage of deformable triangular particles. Using this, plaster-made samples with saw-tooth asperities are modeled and numerical results are compared with experimental measurement. The investigation approves that the proposed DEM is successful of predicting shear response of rock joints.

1 INTRODUCTION

As a discontinuous approach, Discrete Element Method (DEM) is nowadays being extensively used in rock material failure. In fact, rock mechanics is one of the first subjects from which the DEM has been developed. The theoretical foundation of the method is the formulation and solution of equations of motion of rigid or deformable bodies by implicit or explicit formulations. Formulation and development of the DEM have progressed over a long period of time since the pioneering study of Cundall (1987). Jing and Stephansson (2007) have extensively provided fundamentals of the DEM and its application in rock mechanics. In this paper, UDEC (Itasca 2009) is chosen as the computational tool. The code is developed by the authors to adopt a new constitutive law for the contacts and produce random-shaped triangular particles. It will be shown that the proposed model precisely reproduces compressive and Brazilian test results of a plaster, as typical rock material. At the next step, plaster rock joints will be reproduced using the microparameters formerly obtained. Comparing the results with those experimentally measured by Yang&Chiang (2000), the adequacy of the developed DEM model to effectively predict joint shear failure and strength is verified.

2 EXPLICIT DYNAMIC DISCRETE ELEMENT METHODOLOGY

Dynamic modeling in UDEC permits 2D plane-strain analysis. The solution scheme is identical to that used by the explicit finite difference method for continuum analysis.

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