Studies Of The Two-dimensional Continuum-discontinuum Method Based On Potential Contact Force

In order to improve the continuum-discontinuum method which is developed by us,a contact detection method based on space partition is adopted to improve the efficiency of the contact detection;the potential contact force is introduced to reasonably solve the corner-corner contact problem;a program is designed based on the object-oriented thought to improve the expansibility of the program;the parallel acceleration technique based on OpenMP is used to optimize the original serial program to improve the speed of computing.Effects of three types of loading,i.e.concentrated loading,plate loading and flattened loading,on the macroscopically mechanical behaviors,tensile strength and cracking processes of Brazilian disks are numerically investigated based on the continuum-discontinuum method.The effect of tensile strengths of materials is presented for three kinds of loading types.In addition,the modified coefficients of tensile strength at different loading angles are presented for the flattened Brazilian disks.It is found that the disk at flattened loading easily cracks at its center,while the disk at concentrated loading or plate loading is subjected to the shear failure at two loading ends;when the disk cracks at its center,the calculated tensile strength closest to the value used in numerical simulation is obtained by the concentrated loading,the next is the plate loading,and the last is the flattened loading;for different loading types,a lower tensile strength leads to an easier cracking at the center of the disk,otherwise,the disk will be subjected to the shear failure at two loading ends.Numerical simulation of deformation-cracking processes of the rectangular tunnel surrounding rock under different loading velocities is conducted.When stresses acting on rock elements satisfy the shear failure criterion,the stress drop in the form of brittleness is considered,in which the confining pressure remains constant,to validate the present method,numerical simulation of the deformation-cracking' process of a rock specimen in uniaxial compression is conducted.It is found that at lower loading velocities,load-displacement curves of the surrounding rock exhibit a single peak,while at higher loading velocities they exhibit several peaks;at lower loading velocities,the failure of the surrounding rock is progressive,while it is intermittent at higher loading velocities;at the same loading displacement,the cracking depth of two sides of the surrounding rock is larger at lower loading velocities than at higher loading velocities,results at lower velocities are similar to rib spalling of two sides of the surrounding rock,while results at higher loading velocities are similar to rockbursts.