Systemic Study On Engineering Geology Of Long Tunnel In Karst And Gas-Storaging Area

Groundwater, natural gas and other bad geological condition are dominative factors for tunnel construction security, project quality and structure stability of in the long tunnel engineering construction with gas and karst. Based on studying engineering geology of the Yuanliangshan tunnel in the paper, the research systems and basic theories of karst and gas tunnel are established from the karst, gas and engineering environment. The main research contents in the paper are:First, karst geology research. (1) Chemical thermodynamics research in the district of carbonate rocks. The influence of produce and develop of karst function is analyzed by the partial pressure function of carbonic acid and carbon dioxide of groundwater. Based on many comprehensive analytical methods to composition of the groundwater, five chemical reaction equations are designed and carbon dioxide gas partial pressure and the direction of chemical reaction are set up. With the erosion accurately of groundwater, a new theory and a method comparatively of groundwater corroding are offered in the project practice. The corrosion of groundwater shows that the carbonic acid and sulphate and sulphur hydrogen and the reacts of alkalescence aggregate are playing corrosive rule to the concrete.(2) Karst dynamics research in the district of carbonate rocks. According to relation of mineral dissolution and deposition, there are deep bury district and excavated district about a gas storage long tunnel in karst. In the deep burry district of tunnel, with according to the definite chemical model and relative and absolute content of water quality, corrosive amount and corrosive modulus are carried on by the calculation of chemical thermodynamics and chemical dynamics theory and the correlation analytical method, It concluded that tunnel corrosion total modulus in the deep bury district is more than 10 times that of excavated district. Combined methods with chemical thermodynamics, chemical dynamics and the method of groundwater dynamics theory, water dynamics model, chemical dynamics model and some relevant calculation formula are provided in the district of carbonate rocks.(3) Research on karst water outburst and mud outburst. In the paper, the definition, primary condition, essential feature and classification, destructiveness of karst water outburst and mud outburst are discussed. Based on fracture mechanics principle, the hydraulic fracturing was studied in the course of water outburst and mud outburst. The formula of critical water pressure of type II crack and the equation of joint spacing variation are presented. Through destructive analyses ofkarst water outburst and mud outburst, the shock power of the mud outburst, are proposed in the Yuanliangshan tunnel "9.10 "accident. Karst water outburst and mud outburst are simulated by discrete element method; the moving process of water outburst and mud outburst is presented dynamical in the Yuanliangshan tunnel.Secondly, research on natural gas geology. In the paper, the mechanism of gas outburst, gas-solid coupled simulation by discrete element method and natural gas problems in the Yuanliangshan tunnel are studied. Petroleum gas and coal gas are produces in the karst region generally; the author thinks that gas outburst includes coal gas outburst and the petroleum gas outburst in the tunnel construction. Gas migration mechanism and mathematics model, including macroscopic and microcosmic mechanism, migration mathematics model, diffusion models, gas-solid coupled discrete element method numerical simulation of gas migration and mechanism of gas outburst are proposed. Based on the methods above-mentioned and monitoring data, some import problems are studied, such as natural gas storaging character in the entry of Yuanliangshan tunnel, forecast methods of natural gas, relation of natural gas and underground water, kinds of poisonous and harmful gas and its appraising, evaluation indexes of air quality in tunnel, etc.Based on the content above-mentioned, engineering application is studied. Systemic forecast methods of engineering geology are summarized, including TSP engineering geology forecast, geological radar, infrared acquisitions meter, forecast planning survey hole, geology description, engineering geology integrated analyzed, manage method systems, etc. Based on the mentioned methods, forecast of engineering geology are carried on in Yuanliangshan tunnel. Air quality in Yuanliangshan tunnel is analyzed by means of gas monitoring data.The third, research on environmental problems. The long tunnel karst environment and engineering environment are defined initially, the basic characteristics of karst environment and engineering environment are studied preliminary, and karst environment and engineering environmental system are analyzed in the long tunnel. At the same time, effect of tunnel engineering to environment in karst region is studied, the basic condition of karst leakage is analyzed, the classification of karst collapses in the long tunnel is set up, and forming condition and characteristic of karst collapses in the long tunnel are analyzed.Possible effects to environment of underground engineering construction of karst regions usually can presents the activating of ancient karst, increasing of modern karst development, changing of the hydrogeological environment, karst...