Stress Path Dependency Research On Mechanical Behavior Of Hongtoushan Deep Stope Gneiss

With the increase of depth in mining engineering, the geological hazards caused by high stress such as spallings and rockbursts become Increasingly prominent. In order to mining the deep orebody safely and effectively, it is necessary to study the mechanical behavior on deep rock, especially the disturbance by the mining. The depth of Hongtoushan mining has reached1000m, rockbursts and spallings become more and more serious. The gneiss and copper ore from27stope of Hongtoushan are chosen as the research object, the mechanism of deformation and failure of brittle rock in loading and unloading conditions is studied by uniaxial compression test, conventional triaxial compression test and a kind of unloading test. And the strength criterion which is appropriate for gneiss and copper is determined by comparing. The main research works are listed as follows:(1)In order to get accurate test data, systematic and scientific calibration is done. It include the calibration of deformation measurement system and the force measuring system, and low friction spherical seat test and functional testing machine work.(2) By making a analysis of domestic and foreign results of the progressive brittle failure processing on hard rock, the major problem that it is hard to determine the Young modulus and Poisson ratio have been found. On the base of ISRM and moving point regression technique, a new method is presented, which leads to higher reliability on threshold on the gneiss and ore sample. Then the progressive brittle failure processing in triaxial condition is discussed by extend the theory.(3) Using the result of mechanics test, considering the ground stress and mining method of Hongtoushan27stope, numerical simulation is taken for study the impact on ground stress of mining. The area of stress concentration and plastic damage area in the wall rock after mining can be got and the stress path of surrounding is proposed which have certain reference meanings for the test of stress path. (4) By summarizing the research results of the domestic and foreign triaxial loading-unloading test of hard rock, chose initial damage levels which have a significant impact on the rule of rock unloading deformation and failure as the research object. As the dispersivity of the strength, stress level cannot be used to measure the damage level. Deformation rate which base on the lateral and axial deformation during the load is presented.