Simplification Of Discrete Fracture Network And Application In Tunnel Stability Analysis

The numerical methods of rock mechanics can be divided into continuous medium method,discontinuous medium method and mixing method of continuous and discontinuous medium.Traditional numerical simulations usually treats rock masses as continuum material,and directly uses continuum mechanics in material mechanics to analyze rock mass mechanics problems.With the development of discrete element analysis software,great progress has been made in discontinuous analysis of jointed rock mass.However,there are still difficulties and labor intensive in realizing modeling of large number of joints in large scale 3-dimentional jointed rock mass model.Discrete fracture network(DFN)method provided a statistical approximate approach to model real joint sets.But to build rock masses with real joint density is still complicated.Therefore,the simplification of joints number is necessary.This research built rock mass models with DFN method according to the joint development pattern acquired from the research area.With rock mass models,a joint simplification method is proposed and applied to the stability analysis of a tunnel project.The major research contents and results are as follows:(1)The occurrence of outcrop joints is measured and the statistical geometric parameters of joints in the study area are analyzed.A joint rock mass model is established with the 3-dimensional discrete fracture network method using the discrete element method(DEM)based software,3DEC.(2)In the jointed rock mass model,different minimum joint sizes are used to simplify the number of joints in rock mass.The changes of joint density and mechanical properties of rock mass under different simplified conditions are analyzed,and the size of joint simplification is put forward.(3)Based on the data of mining area and high density electrical geophysical prospecting method,the distribution of mined-out area in research area is investigated.A 3-dimensional model of Yudushan tunnel crossing mined-out area is established in 3DEC software with joint simplification method,and the stability of mined-out area and surrounding rock mass of tunnel are analyzed with strength reduction method.