Numerical model for jointed rock mass in particle flow code and its application

To simulate the joint network around mining tunnels and to conduct the stability analysis of tunnels in jointed rock mass, a numerical model for jointed rock mass containing particle flow block model, original joint network and secondary joint network is established. As the orientation and area of internal secondary joints are unmeasurable, a method for calculating the secondary joint orientation and area under unloading is put forward. The unloading direction is calculated according to the change of stress tensor before and after excavation, and the stochastic joint orientation is generated around the unloading direction through the Fisher distribution function. The area and radius of joints are calculated through the change of energy stored in particles. The density and orientations of the original joints in tunnels are measured through surveying lines, and the original joint network is rebuilt by using the Monte-Carlo method. The secondary joint network is rebuilt by using the secondary joint method. Finally, the realistic joint network and jointed rock mass model are established. The calculated result shows that the tensile failure firstly occurs at the top and bottom of the tunnel without joint network, while failure firstly occurs around the oints in the realistic jointed rock mass model. The original joints are mainly sheared to failure, and the failure mode around secondary joints is mainly tensile failure. Failure occurs mainly at the rim of the tunnel, which should be supported firstly. The two side walls of the tunnel should be also supported in particular. This study may provide reference and advice for tunnel calculation in jointed rock mass.