Study On Strength Degradation Law Of Surrounding Rock Of Deep Roadways

In allusion to the engineering background of a roadway embedded about one kilometer underground in Shandong Yuncheng Mine, study is taken to get the strength attenuation law of surrounding rock by ways of true triaxial physical simulation, rock sample test with MTS, theoretical analysis and numerical simulation. The main research contents and conclusions are as follows:(1) With WYQ1000-I large scale three-dimension test system for underground engineering simulation, the full unloading process of surrounding rock of a deep roadway is physically simulated. The results show the failure patterns of surrounding rock without support, and the actual loading-unloading paths and stress states of the surrounding rock in different distances from roadway periphery. Based on the test data, this dissertation analyses the evolution law of deviatoric stress in broken rock zone of the roadway, establishes the corresponding relation between damage degree of surrounding rock inside the broken rock zone and its decreased degree of deviatoric stress at post-peak.(2) According to the stress paths of the surrounding rock obtained by physical simulation, rock samples are tested on the MTS test machine. First, the rock specimens which have the same damage extent with the surrounding rock are obtained. Then the strength and deformation parameters of these specimens are measured under different confining pressures. By analyzing the test results, the author gains the law of strength attenuation of injured rock samples and the influence of confining pressure on strength attenuation extent, establishes the post-peak strength degradation model of rock around the deep roadway by setting the relation between strength parameters and two damage factors (i.e., stress reducing ratio Dσand volume expansion ratio DV).(3) The post-peak strength degradation model for surrounding rock of a deep roadway is embedded in FLAC3D numerical simulation software. Using the software, further study is done on the evolution law of stress (especially the emphasis is placed on the deviatoric stress) and strain fields in the fracturing process of rock surrounding the deep roadway. The results of numerical simulation are compared with the indoor physical simulation as well as the in-site measurement, which verifies the rationality of the model.(4) Based on the fact that the surrounding rock strength attenuation is usually coupled with fracture expanding and penetrating, fractured rock samples with different distributions of discontinuities are tested under zero confining pressure to study the relation between the strength degradation, energy feature parameters and the damage extent of surrounding rock. The functional relation is developed between peak strength, energy feature parameters at peak point and fractal dimension D. Furthermore, the acoustic emission features in the refracturing process of damaged rock samples are investigated under uniaxial compression.This article includes 95 images, 34 tables and 136 references.