a. Faculty of Engineering, Nagasaki University, Bunkyo Machi 1-14, Nagasaki 852-852 l, Japan
b. Graduate Student, Graduate School of Engineering, Nagasaki University
c. Institute of Environmental Systems, Kyushu University, Higasi-ku, Fukuoka 812-8581, Japan

A rock mass in in-s it~ is not continuum and its mechanical behaviour is strongly affected by the behaviour of the existing discontinuities, such as bedding, joints, faults and fractures. Several experimental and numerical Investigations have demonstrated the influence of discontinuities on mechanical, thermal and hydraulic behaviour of jointed rock masses. It has also been indicated based on the experimental and in-situ investigations that deformational mechanism and stability of rock structures in the discontinuous rock masses extremely depend on not only the existing discontinuities but also new cracks, which are generated and progress due to loading and/or excavation.
This study is to develop an expanded distinct element method (EDEM) for simulation of generation and progress of new cracks due to shear and tension failure in the matrix blocks. As the applications, changing the depth of opening and geometrical distributions of the existing discontinuities carries out excavation simulations of deep underground opening. For the verification of the proposed approach, scale model experiments by using the base friction experiment apparatus are also carried Out. Finally, effects of cable bolts on controlling deformations of the rock masses surrounding opening and movements of key blocks are discussed.