Experimental And Numerical Research On Crack Propagation And Anchoring Mechanism In Jointed Rock Masses

The failure of jointed rock mass was usually caused by the initiation, propagation and coalescence of new wing cracks derived from primary joint. The rock bolt is applied successfully in the reinforcement of rock slope and tunnel excavation, but the specific stress analysis in the sector of the bolt was still not been clearly resolved. The keys of learning bolt reinforcement include ensuring the rule of mechanics transfer, setting the stress model of contact adopting the reasonable numerical computation method.The mechanism of crack initiation and propagation is studied using rock-like modeling material. Rectangle prismatic specimens with an oblique central crack (a pre-existing flaw) are used in the experimental study. The crack propagation process is observed in the specimens under uniaxial expression. Two types of branch cracks, i.e. wing cracks and secondary cracks are found through experiments. The extended finite element method (XFEM) is applied in modeling the crack growth under uniaxial compress load in the rock-like materials. First, the implementation of XFEM is incorporated into a commercial FEM software (ABAQUS) in which the constitutive law of linear elasticity and the criterion of maximum tangential stress (MTS) is adopted. Then a user subroutine is coded and incorporated into ABAQUS to simulate the growth of wing crack in the crack faces. A series of numerical simulations of3D (2D) rectangle with central pre-set crack are carried out, and computed results are compared with experimental ones. The effects of inclination and coefficient of the friction of the pre-set cracks on growth of wing cracks are examined. In addition, size effect of materials is also investigated, and these jobs contribute to the understanding of crack growth.This paper attempts to departure from the continuity theory of the force in the anchoring segments, and defines the softening curve of the shear stiffness based on the assumptions of interfacial shear stress redistribution. Through the ABAQUS software with spring model, a numerical model of a typical pull-out test is built whose results is compared with actual test ones, which shows the maximum pull-out load is influenced by many factors that change the dimension and strength of the grout. The above results also confirm the consistency between the simulation results and actual ones. Based on3D FEM, with the form of a combination of normal solid elements and cohesive element in ABAQUS and the definition of contact between rock joints, the interaction of bolt-grout and grout-rock was simulated in the jointed rock mass anchored with full grouted bolt under shear loading. Further, the bolt reinforcement effect of rock mass was revealed.