Study On Mechanical Characteristics Of Statically Loaded Rock Under Dynamic Loads

It is necessary to mine deep resources for the shallow resources are increasingly exhausted in the world. However, as the underground human activities (deep mining, nuclear waste storing, oil extracting and geology drilling etc.) stepping deeper, the in-situ stress increases nonlinearly, the ground temperature rises higher, and there also have lots of other phenomena such as rock burst in deep shaft, rock brittle-ductile transition, abnormal failure characteristics, zonal disintegration and so on, which are not well explained by the existing rock mechanics. Why do the questions occur? In fact, during the exploitation of resources in deep, rock is already in the condition of high static stress or ground stress before they are subjected to dynamic stress such as blasting vibration. Rock stability can be well solved by existing rock mechanics due to small buried depth and low ground stress in shallow rock mass, but it is not the case for rock in deep. Therefore, the researches of rock mechanics and mining engineering at present emphasized on mechanical behavior of high statically loaded rock under dynamic loads. For these questions above, systemic theoretical and experimental researches of rock mechanical behavior under static-dynamic coupling loads in one and three dimension are carried out in this paper with the support of the National Natural Science Foundation of China.The improved SHPB testing system which can load static axial pressure and confining pressure is employed to carry out static-dynamic coupling loading test. The mechanical response and failure characteristics of sandstone loaded by stress wave under different axial and confining pressure are studied. In the research of mechanism, the stress fields are calculated under different loads and the crack growth process is simulated through numerical software based on the cylinder model with a penney crack in. Thus, the fracture and failure mechanism of high stress rock is analyzed under dynamic loads, a new mechanical constitutive model under static-dynamic coupling loads is established with different machine elements, and the rule of strain energy density is researched.On the aspect of constitutive relationship, rock is made up of many microstructures constituted by self-similar machine elements, and a constitutive model of rock under uniaxial or triaxial static loading plus dynamic loading is established by way of combining microstructures with different mechanical properties.On the aspect of strength theory, strain energy density is used to define a failure/fragmentation criterion of the rock under static-dynamic coupling loading. According to Conservation of Energy, a formula calculating strain energy density is obtained. The strain energy density during rock failure is deduced based on the constitutive model of rock under coupled static-dynamic loads, and the critical value of rock strain energy density under static-dynamic coupling loading is derived.In engineering application, we think that the rock laboratory experiments may simulate and reshow rock bursts considering the conditions of coupled static-dynamic loads and rock burst and their comparison. Energy demand of rock burst occurring is revealed through analyzing energy transition of rock failure process under coupled static-dynamic loads. At the same time, the rule of energy utilization under coupled static-dynamic loads is discovered; the measures for rock cracking by utilizing high stress condition in deep rock mass and energy utilization improving are found.The characteristics of rock failure under coupled static-dynamic loads and the problem in engineering are researched in this dissertation based on the subject frontier, various theoretical and experimental methods. The results of this dissertation are useful both theoretically and practically, and established the foundation for systemically researching the mechanical characteristics of rock mass in deep.