Anisotropic Permeability Of Fractured Rock Mass And Its Application In Underground Crude Oil Storage Caverns Subject To Groundwater Curtaining

With the rapid development of geotechnical engineering, permeable properties of fractured rock mass and groundwater movement which affect the stability of underground engineering have attacked increasing attentions over the world. As an important basis of geotechnical engineering theory and application technology, the research and evaluation methodologies on the permeable characteristics of anisotropy fractured rock mass play a crucial role geotechnical engineering.The mechanical and seepage characteristics of rock mass are different from homogeneous medium. Being situated in a certain geological environments, complex geological bodies were formed over a long geological period of time. Rock mass consists of continuum rock and discontinuous geological structural planes. The complexity of the structures of rock mass leads to seepage anisotropy.In geotechnical engineering construction process, the engineering excavation changes the internal stress distribution of the rock mass, thereby changes its structure, eventually changes its permeability characteristics and the movement of groundwater. On the other hand, the geotechnical engineering disturbs the balance of groundwater field by changing the conditions of recharge, runoff and discharge. Therefore, the analysis of fractured rock mass permeability characteristic and groundwater movement law has important significance to ensure engineering stability, which is an important issue of common concern of geotechnical engineering andalso has theoretical and practical engineering significance.Based on the above reasons, the researches on the fractured rock mass permeable properties and groundwater movement in engineering activities is important in the guarantee of the stability of underground projects. It is a topic with theory value and practical engineering applicationBased on the permeability tensor theory of fractured medium and the fluid-solid coupling theory, this study focus on the study of the fractured rock mass anisotropic permeability and the fluid-solid couping movement law by using the research method which contains the data analysis, the theoretical research, the numerical simulation and comparison analysis. The application of the anisotropic permeability into an underground crude oil storage caverns subject to groundwater curtaining at Huangdao is performed. The main contents are as follows:(1) Based on the study of variety seepage theories of fractured rock mass and permeability tensor model with parameters about fractured system connectivity and cut-through property, three-dimensional fractured roc system connectivity and cut-through property, three-dimensional fractured rock mass permeability coefficient tensor formula was deduced with taking fracture structure surface roughness into single cranny hydraulic conductivity calculation.(2) According to geological and hydrological data and statistical analysis of surface fractures and drilling fractures, permeability coefficient tensor of the study field was calculated using the improved permeability coefficient tensor formula. Two-dimensional model of survey region was built by multi-physical coupling software, namely, COMSOL Multiphysics. The theoretical calculation of the fractured rock mass permeability tensor was calibrated and permeability tensor correction factor of the survey regional was obtained.(3) Simulations of two different physical fields:unitary seepage field and seepage-stress coupling field in the study of the area were conducted using the2D model. Isotropic and anisotropic cases were adopted in the calculation for the two physical fields as well. Comparing the calculated results to actual drilling observation data, the results under anisotropic condition in seepage-stress coupling field were more realistic than those under isotropic condition.(4) There-dimensional model of the underground crude oil storage caverns was built. The numerical simulation of the seepage field and stress field about storage caverns during construction and operation was conducted. The predicted results may provide guidance for engineering practice.