| The prediction and damage mechanism of rock mass is an important part of rock mechanics research,and shear and tension are the most common form of rock mass instability.A large number of theoretical and experimental phenomena show that the emission of the rock is accompanied by the dissipation of energy under the action of the external load,and the acoustic emission is directly related to the microfracture(damage)in the rock.The acoustic emission characteristic parameter has a"proportional"relationship with the rock damage,The characteristics of the acoustic emission signal under the external load can provide a strong basis for the prediction of catastrophic evolution.In this paper,the experimental and numerical simulation of the combination of research methods,the rock fracture process of acoustic emission signal characteristics of the analysis.(40~o,50~o,60~o)shear test,the acoustic emission in the loading process is detected by the compact tensile test of granite and the deformation angle of the sandstone.The characteristics of the acoustic emission signal under tensile and shear conditions are analyzed.Then,according to the fracture mechanism of tensile and shearing,the numerical simulation of the test process is carried out by using the finite element program of Ansys,and the basic laws of the rock fracture evolution and the characteristics of the acoustic emission signal are obtained.The main conclusions are as follows:(1)The rock fracture process has the characteristics of stage evolution,ie,nucleation stage and crack propagation stage.Correspondingly,the acoustic emission signal characteristics also show the characteristics of the stage change.(2)Nucleation stage,is the micro-defect nucleation,gathered to form micro-cracks stage.In the initial stage,the acoustic emission signal is discrete and random in time,and the parameters such as the corresponding amplitude are small.The intensity of the nucleation signal increases rapidly until the macroscopic crack nuclei are formed,and the signal intensity reaches the peak.In the subsequent crack During the expansion phase,the acoustic emission signal exhibits a tightly distributed distribution in time,but the amplitude decreases gradually.(3)During the whole rupture process,the peak time of the acoustic emission signal is slightly behind the external load peak.(4)The compact tensile damage acoustic emission signal is dominated by the tension source.The shear failure acoustic emission signal is caused by the tension source and the shear source.(5)Using Ansys software to simulate and experiment with each other,it helps to reveal the evolution process of fracture completely and completely.Because the experimental loading process is not controllable,so that the information parameters after the peak can not be recorded;and numerical simulation in the loading process is controllable,it can fully show the rock damage-fracture evolution of the whole process.Finally,as a possible application path,this paper presents a model of rock microcracking scale growth based on acoustic emission signal sequence. |
