Study On Stability Of Underground Caverns And Support Technology In Deep Layered Rock Mass

With the development of our national economy, it is necessary to exploit mineral resources massively and construct infrastructures at large scale. In the nature, layered rock mass takes account for about two-thirds of the land area, while in China the proportion is as high as77.3%. Thus, the large-scale construction projects that will encounter the problem of stability of the layered structure of rock mass. Structural plane of the layered rock mass will result in the highly orthotropic characteristics of the layered rock materials and its stability analysis is also affected by many factors. According to the operating conditions of the deep sinking and driving engineering in the Shabatu mine of Kailin Group, the responses of underground chambers to mining operations, such as the mechanical properties, deformation-to-failure characteristics, macroscopic failure modes and surrounding rock stability, were investigated by means of theoretical analysis, field tests and numerical simulation etc. The main research contents were as follows:The researches on the layered rock-mass failure mechanism and criteria were reviewed and discussed. Considering the engineering practice in Shabuta mine, the discrete element method based on discontinuum was applied to study the geotechnical engineering problems with developed joints and large deformation by comparing various numerical methods which could describe the characteristic of anisotropy in the layered rock mass.Laboratory tests on the mechanical properties of bedded red shale rock containing a single set of joints were performed. The mechanical parameters of rock and bedding surface were obtained and also the above-mentioned anisotropic characteristics and failure modes were exposed.Posterior to in situ tests, the newly-excavated surface deformation and the internal surrounding rock deformation were measured and the chamber failure modes after excavation were monitored and observed. Consequently, the surrounding rock deformation and failure modes happened in deep soft bedded rock with high stress were obtained.Numerical simulation on the stability of underground chambers was carried out. Combined with the field test results, the deformation failure mechanism of deep soft bedded rock with high stress was analyzed.The effects of influencing factors on the chamber stability, such as the bed thickness, the inclination of rocks, the burial depth of chamber, the elastic modulus of rock mass as well as the tangential stiffness of joint surface were investigated by using orthogonal design method. After detecting the visibility of multi factors and the sensitivity of single factor, the rule of these factors affecting the surrounding rock stability was obtained.From the technological and the economic aspects, the control measures to restrict the likelihood of large deformation in deep buried bedded rock were proposed. And a optimal scheme was determined by simulating the working scenarios numerically. Based on the optimal control scheme, further optimization analysis to the length of rock bolts was conducted. The practical application effects were verified through field tests.