Study On The Mechanical Properties Of Rock Unloading Crushing Under High Stress

With the rapid development of economy,the global shallow resources can not meet the needs of social progress.At the same time,the scale and development depth of underground engineering in open-pit mineral resources,coal mining and other industries are increasing rapidly.Before excavation,the surrounding rock is in a relatively stable and balanced stress field.After excavation,the surrounding rock is released at the free surface of excavation,and the stress of surrounding rock is redistributed within a certain range.Under the action of stress,the surrounding rock appears deformation,the weak part of surrounding rock even appears local failure,and even the overall failure of the project appears on this basis.Therefore,it is an urgent problem to study the mechanical properties of rock mass and make clear the failure mechanism of engineering rock mass.Based on this,the mechanical properties of unloading failure of rock under high stress are studied in this paper.According to the actual project excavation design path scheme,using the method of combining indoor test and theoretical analysis,taking Wunugetushan copper molybdenum mine in Inner Mongolia and Mirador copper mine in Ecuador as the engineering background,taking granodiorite and porphyry granite as the research object,uniaxial compression test,conventional triaxial test under different confining pressures and confining pressure relief test before peak are carried out to analyze the strength and deformation characteristics of rock;According to the test results of pressure relief before the peak of granodiorite and porphyry granite,the strength criterion in line with the actual project is determined.The research results of this paper can reasonably predict the strength and deformation characteristics of similar engineering rock mass,and provide reasonable suggestions for similar engineering construction and support.The main research achievements of this paper are as follows:(1)The strength and deformation characteristics of granodiorite and porphyry granite under different confining pressures were studied by using GDS electro-hydraulic servo controlled rigid testing machine.(2)Based on the pre peak unloading confining pressure test,the deformation modulus and Poisson's ratio of granodiorite and porphyry granite show nonlinear relationship with stress difference under different confining pressures.(3)Based on the pre peak unloading confining pressure test,when the confining pressure of granodiorite is about 56.2%-69.7% of the initial confining pressure(the average value is 62.95%),and when the confining pressure of porphyry granite is about 67.4%-79.1% of the initial confining pressure(the average value is 73.25%),the stress difference of rock sample drops sharply,loses stability,and finally leads to failure.(4)Based on the pre peak unloading confining pressure test,two parameter Mohr strength criterion,parabolic Mohr strength criterion and nonlinear power function Mohr strength criterion are used for comparative study.The results show that the nonlinear power function Mohr strength criterion is more consistent with the analysis and application of this paper.