ABSTRACT

Numerical simulation of joint in rock mass is always a research focus. For simplification, most studies treat joint as a smooth one, while the real joint in nature is rough. At present, few numerical simulations focus on the rough joint, and there are few studies about hydraulic, mechanical and dynamic behavior of rock mass with rough joints. This paper proposed a new method called SAW method to simulate the rough joint. Relationships between step number N and joint roughness coefficient JRC and between standard deviation of undulating angle and JRC are studied in the simulation. It is concluded that step number has a reciprocal relationship with JRC and standard deviation of undulating angle has an exponential relationship with JRC. Fixing JRC, standard deviation of undulating angle should be determined using the related truncated distribution. This paper provides a certain basis for studying the hydraulic, mechanical and dynamic behavior of nature rock mass.

1 INTRODUCTION

Because of the importance of rock joint, the simulation for joint network in rock mass is always a research focus to domestic and foreign scholars. Most studies are based on two hypothesizes that the joint surface is smooth. As we know, they don't accord to the nature situation. The roughness of joint has a very significant influence on hydro-mechanical characteristic of rock mass. This point has obtained many attentions and the related researches are done. Barton (1977) proposed the conception of joint roughness coefficient JRC and gave out an empirical method to determine JRC and pointed out that JRC varies from 0 to 20 through tilt, push and pull test. The relationship between JRC and shear strength of rock mass is finally obtained. Considering the scale effects, Barton (1982) gave out a modified formula for JRC through some laboratory test. Reeves (1985) gave a general introduction for various statistics to describe rock surface roughness and classified them into two categories: one describing the magnitude of the roughness and the other one describing the texture of the rough surface. To decrease the dependence on the sampling length, he used the average asperity gradient to describe the roughness of joint, instead of root mean square gradient. The friction angle of joint is predicted through this. In his simulation, the statistical parameters such as undulating height are assumed to have a Gaussian probability distribution. About the measurement of roughness for joint surface, the earliest method is to compare with ten standard roughness profiles which are proposed by Barton. And there are big artificial error using this method. Then Barton proposed the straight edge method where the JRC is obtained according to the undulating height of different sampling length. Du Shigui et al (1996) pointed out that the geometrical shape of joint surface consists of three parts: macro geometrical profile, fluctuation shape of surface and micro roughness. And he also pointed out that fluctuation shape of surface is the decisive factor for the mechanical characteristic of joint.

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