Abstract:According to random joint program,several groups of numerical models on random joint rock mass are obtained. The stress-strain curves of these models are gained by numerical test. Firstly,the changing law of the deformation curve on these numerical samples under certain confining pressure is considered under the same probabilistic distribution parameters of random joint and the same sample size conditions. Then,the effect on the stress-strain curve caused by sample size is considered. Through the above two kinds of computing schemes,it is found that the deformation curves become dispersal when the sample is small,and become uniform with the enhancement of size. It illustrates that the size effect exists among these curves,and the size of rock mass deformation feature can be obtained by numerical test.