| In the process of tunnel shield construction,there are usually a large number of joints in rock mass.Jointed rock mass is easy to be destroyed,resulting in the engineering accidents such as collapse.The joint plays a decisive role in the stability of rock mass and the potential failure direction of tunnel.In this thesis,the finite element method was used to simulate the fracture of jointed rock.Firstly,the influence of different joint characteristics on fracture characteristics of rock without hole and rock with different tunnel shape holes was studied by uniaxial compression.After that,the simulation of rock breaking under TBM cutter was carried out for jointed rock.This study can improve the understanding of the mechanical behavior of jointed rock,strengthen the understanding of the failure mode of tunnel in jointed rock mass,and has guiding significance for tunnel construction.The main contents and conclusions of the study are as follows:（1）Finite element models of intact rock and rock with different tunnel shaped holes were established in ABAQUS by cohesion method.Firstly,cohesive elements were inserted into the common surface of solid elements,and the bilinear constitutive model proposed by our research group was used to determine the initial damage and final failure of cohesive element to simulate the process of crack generation and propagation.The uniaxial compression experiment of rock was simulated,and the simulation results were compared with the experimental results in the literature,which verified the correctness of the rock model.Furthermore,the finite element model of jointed rock was established by using free surface to simulate rock joints,and the uniaxial compression simulation was carried out.It was found that this method could well simulate the crack generation and propagation at the joint tip and the crack coalescence between joints.（2）The influence of joint inclination angle on fracture characteristics of rock without hole and rock with different tunnel shape holes were studied by uniaxial compression simulation,and the fracture process was observed.The results show that the uniaxial compressive strength and Young’s modulus decrease first and then increase with the increase of joint inclination angle.There are four kinds of cracks coalescence between joints and three kinds of cracks coalescence between joints and holes.The types of cracks coalescence are affected by the joint inclination angle.At the same time,the influence of joint continuity factors which contain the joint length,the joint spacing and the bridge length on rock fracture characteristics was studied,and the fracture process of jointed rock under different continuity conditions was analyzed.The results show that the joint length and the joint spacing have a great influence on the mechanical properties of rock and the types of cracks coalescence between the joints,while the length of bridge has a relatively small effect.（3）The simulation model of TBM cutter breaking rock was established,and the influences of the confining pressure,the joint inclination angle and the joint continuity on rock breaking characteristics of TBM disc cutter were studied respectively.The fracture process of rock,the contact force between the disc cutter and rock and the crack area of rock were observed under different characteristics.The results show that the confining pressure,the joint inclination angle,the joint length,and the joint layer number have a great influence on the contact force and crack area,while the influence of joint spacing and bridge length are relatively small. |
