Rock Fracture Simulation Based On Meso Structure With Discretised Virtual Internal Bond

Rock is composed of mineral grains on the meso-scale.Such mesostructure determines the macro mechanical properties of rock.To effectively simulate the macro fracture behaviors of rock,the discretized virtual internal bond(DVIB)is employed to model the mesostructure.DVIB is a newly-developed lattice model.It consists of lattice bond cells and each bond cell can take any geometry with any number of bonds.A lattice bond cell can be considered as a mineral grain,thus the DVIB can capture the mesostructural characteristics of rock.Prior to mechanical modeling,the real mesostructure of rock should be obtained by experiment.To calibrate the meso mechanical parameters,the macro mechanical parameters should be obtained through physical test as well.To get the mesostructure and the macro mechanical parameters of different rocks,the granite,marble and sandstone are tested respectively.To test the tensile strength of rock,the Brazilian disc test is carried out.To test the uniaxial compressive strength and deformation modulus of rock,the uniaxial compressive test is conducted.To obtain the macro fracture energy parameter,the three-point-bending test is carried out.To obtain the mesostructure of rock,the slices are taken from the fracture faces of three-point-bending sample.Through the Scanning Electron Microscope and the Optical Scanning on the rock slices,the mesostructure of rock is obtained.By the digital image processing,the clear mineral grain picture is obtained.Based on the grain structure,the DVIB mechanical modeling isestablished.To more accurately model the mineral grains,the 3-node(3bonds)-and 6-node(15 bonds)triangular cell are adopted respectively.To balance the efficiency and accuracy of fracture simulation,at the near-fracture zone the DVIB model is adopted.At the rest zone where the small deformation occurs and the material is almost in the linear elastic stage,the continuum model is used.During fracture propagation,the elastic continuum zone ahead of fracture tip is continuously transformed into the DVIB zone.Such transform process is irreversible.This method is used to simulate the three-point-bending test.The simulation results reasonably agree with the tested results,which suggests that the present method is effective.For the concrete has the similar properties as rock,the present method is extended to simulate the fracture process of concrete.The simulation results are well consistent with the according test results.The present thesis provides a simple and effective mechanical modeling and numerical simulation method for rock fracture.