Due to the stress redistribution after excavation, the pre-existent joints or cracks will deform and new cracks will initiate and propagate in surrounding rock, especially in the plastic zone. And differences, once cracks initiate and propagate in a certain area, exist when the equivalent continuum mechanics and non-continuum mechanics are used to analyze its mechanical response. A method is proposed in this paper to approximately simulate continuum before cracking and to change the potential joints to joints after cracking beginning which can approximately take the effects of cracking into consideration. And this method is explained, in detail, from its computation procedure, the determination of initial material parameters, the distribution of potential cracks and the failure criteria for the real and potential joints. Finally, two sets of numerical analyses are made to verify its effectiveness in approximately simulating continuum and the cracking process.
After the excavation of roadways, the stress in surrounding rock, according to the solution of Elasticity, will range from in-situ stress far away to zero at the surface of the roadway in the radial direction. It means that the excavation brings about unloading for the surrounding rock in radial direction. This stress redistribution will definitely promote the generation of cracks. And the area with cracks is different from that without cracks, especially considering the dilatancy caused by the slip along a persistent cracks and the opening of cracks resulted from the unloading in surrounding rocks. The effects of cracking should be considered to achieve better analysis of the stability of roadways. Nowadays, there are two ways to take the effects of cracking into consideration: the equivalent continuum mechanics and the non-continuum mechanics. To achieve that, the equivalent continuum mechanics method considers the discontinuous rock mass as a continuous medium and the effects of cracking will be reflected by the reduction of strength parameters and the increase of deformation parameters, while the non-continuum mechanics method thinks the rock mass as a discrete medium and the effects of cracking can be considered alone. Thus, the non-continuum mechanics is more suitable for the simulation of cracking in surrounding rock of roadways.
