It is fundamental to understand the process of crack initiation and propagation of intact rock to clarify the coupled hydro-mechanical properties due to the stress change in underground. We have been working on the study of coupled shear-flow properties on sedimentary rock using pumice tuff, Japan. The changes of shear stress, normal stress, flow rate and process of fracturing on sample surface have been investigated by using a new type coupled shear-flow test apparatus. In this study, we designed a numerical model for the coupled shear-flow test using a discrete element code. We report the comparison between the experimental results and the simulation results. The porosity changes of model showed good agreement with the flow rate behavior of the test.

1 Introduction

New fractures due to underground excavation or fault cause mechanical and hydrological problems in underground (Tsang et al., 2005, Mitchell and Faulkner, 2009). The fractures are generated through a variety of mechanisms with various scales (Bossart et al., 2002, Scholz et al., 1993). For the research of underground disposal or geological evaluation, it is necessary to investigate the coupled hydro-mechanical behavior of rock (Olsson and Barton, 2001, Li et al., 2008). We conducted an experimental study on coupled shearflow properties of sedimentary rock, and designed a numerical model for the coupled shear-flow test using a three-dimensional simulation tool, PFC3D (Particle Flow Code3D, Itasca Inc.). The purpose of this study is to examine the performance characteristics of the numerical model. The test system and model are briefly introduced, and the results are compared focusing on stress, permeability and crack propagation.

2 Particle Flow Code3D

PFC3D is classified as a discrete element code (Cundall and Strack, 1979, Potyondy and Cundall, 2004) based on the definition in the review by (Cundall and Hart, 1992). It allows finite displacements and rotations of discrete bodies (including complete detachment), and recognizes new contacts automatically as the calculation progresses. PFC3D can be considered as a simplified implementation of the DEM because of the restriction to rigid spherical particles.

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