Study On Mechanical Properties And Damage Evolution Of Jointed Rock Mass By Particle Flow Code

With the rapid development of long highway tunnel construction in China,the geological conditions of the tunnel are becoming more and more complex during the construction process.especially the existence of rock joints and fissures in tunnel surrounding destroies the integrity of rock mass,and affects the stress and deformation of surrounding rock burst mode directly,and brings great potential safety hazards to the construction of the tunnel.Therefore,it is of great significance on theoretical and practical to study the mechanical properties and fracture mechanism of the rock mass of the tunnel,which can lay a theoretical foundation for improving the technology of engineering geological disaster prevention and control and the level of tunnel construction.In this paper,uniaxial compression and triaxial compression simulation tests were carried out by means of field investigation,theoretical analysis and numerical simulation of discrete particle flow based on Hongtuzhang tunnel.Combined with the stress-strain curve analysis,the mechanical properties of the fractured rock mass of the tunnel were studied and the relevant mechanical parameters were obtained.The damage evolution and fracture mechanism of the fractured rock mass were studied from the micro and macro aspects.The conclusions are as follows:(1)According to the information of survey borehole along Hongtuzhang tunnel,the geometric parameters such as the tendency,inclination,mean length and linear density of joints and their probability distribution types were investigated,and two-dimensional random fracture networks of rock mass in the tunnel area were established.Based on this fracture network,the representative elementary volume unit was calculated to be 10×10m.(2)According to the characteristics of stress-strain curves of fractured rock mass,it is known that the fractured rock mass shows obvious elastoplasticity,and the stress-strain curves of granites with different degrees of weathering were divided into four types.The compressive strength and elastic modulus of fractured rock mass showed obvious anisotropy.The joint distribution in rock mass was an important reason for this phenomenon The plastic deformation capacity,strength and ductility of fractured rock mass under confining pressure were obviously improved.and the cohesion c and internal friction angle ? of the weathered granite engineering rock mass were determined.(3)The initial damage and load damage were established by combining the elastic modulus reduction of the fractured rock mass and the Weibull material strength model.The damage evolution model and damage constitutive model of fractured rock mass were used to explore the damage evolution process and fracture mechanism of fractured rock mass.The model could well characterized the mechanical characteristics and damaged evolution of fractured rock mass under uniaxial compression.The initiation and propagation of microcracks at the joint tip constituted the damage evolution of fractured rock mass.The microcracks grew slowly in the elastic phase and accelerate in the plastic phase.The peak strength point was the inflection point of microcrack development.In the residual deformation phase,the microcracks almost no longer develop.