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Abstract On the background of an open-pit rock masses，some rock mechanics laboratory and field tests are implemented. Based on the particle flow theory and PFC3D(particle flow code in 3 dimensions)，equivalent rock mass(ERM) technique is used to construct ERM model，which reflects the distribution feature of the joints and meso-scale fracture effect. A load-unload code is developed by Fish language in PFC3D to study the strength and mechanical effect of the rock mass. Some study results are drawn as follows：(1) Under the condition of uniaxial compression，the axial stress-strain curve of ERM is divided into three stages，which includes elastic deformation，plastic deformation of unsteady fracture and deformation of post-failure. Compared with standard rock samples，compressive strength and elastic modulus of the ERM are significantly decreased. (2) With increase of confining pressure，compressive strength，residual strength and plasticity of ERM are enhanced. (3) The ERM technique efficiently can describe rock mass anisotropy induced by joints distribution. (4) Microcrack in ERM is distributed and extends along strike direction of joints. Therefore rock mass failures are controlled by properties of the dominant joints.
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Received: 25 February 2010
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