Abstract: Based on the MontCarlo method， the structural plane network of jointed rockmass was generated， and it was used to build the finite element model of rockmass through numerical code RFPA2DDIP， where the microstructure of rockmass was considered. Numerical tests on six rockmass samples with different size of rocks were carried out under uniaxial compression loading， the stressstrain relationship of jointed rockmass was studied， and the size effect of compressive strength and deformation modulus were analyzed. After the failure process of jointed rocks with different scale were examined， the failure process of 1500mm×1500mm rockmass was described. The results showed that compressive strength and deformation modulus declines with the increasing size of jointed rockmass， but the variable range became narow gradually， the compressive strength tends to stabilize faster with the increasing size， and the fitting relation about exponential decay was obtained. The failure processes of jointed rockmass with different scale was similar. The method can offer a new tool to research macromechanical parameters of jointed rockmass.

Key words: jointed rockmass, compressive strength, deformation modulus, size effect, failure process