| The improvement and development of domestic railway network poses an increasing demand of deep, long mountain tunnels. It's a challenging technical problem to build tunnel in high hydraulic pressure karsts area at home or abroad, particularly under the current stringent environmentally-friendly prerequisite, therefore the conventional philosophy 'drain firstly, drain and stop' should be updated with 'stop firstly, drain slightly'. Correspondingly high hydraulic pressure problem is inescapable and it is of significant application importance to investigate the distribution of water pressure in ground, grouted ring, lining back of deep tunnel subject to high hydraulic pressure, and the impact upon the ground stability and structural stress. Fortunately the key problem, which is inescapable during the phase of design, construction and operation of underground engineering (particularly of deep, mountain tunnel) has aroused tremendous attention from men of insight worldwide. Systemic research is carried out aiming at the former-mentioned problem based on the case project of YuanLiangShan deep, very long tunnel in ChongQing-HuaiHua railway.Scopes and Methodologies:1, Based on the synthetic analysis of water pressure reduction coefficient towards hydraulic tunnel, adding the difference of structure, waterproof and drainage style between railway tunnel and hydraulic tunnel, the concept "coefficient of water pressure action' was put forward. Using indoor 3D model experiment method to investigate the rule of hydraulic pressure distribution variations in the process of construction in homogeneous or jointed rock, centering on the water pressure at lining back and outer surface of grouted ring, and the relationship between hydraulic pressure action coefficient and other parameters such as coefficient of permeability and thickness of surrounding rock, grouted ring and lining, and controlled drainage volume.2, Using theoretical method to analytically formulate the water pressure at outer surface of grout ring and lining back in case of railway tunnel waterproof and drainage style, and to analyze the relationship between water pressure and other variables at lining back. Through the research of seepage field numericalmodel, equivalent continuum model and numerical method were used to analyze the distribution of tunnel seepage field, and rule of water pressure distribution and coefficient of action on surrounding rock, grouted ring and lining as well.3, Based on analysis of the geological report of Yuanliangshan tunnel, hydro-geological structure model, ground water system model and ground hydrodynamic model were obtained; particularly detailed analysis of deep hole pressure water and pumping test result, coefficient of permeability and coefficient of permeability tensor of tunnel adjacent surrounding rock were obtained, which verified the selection of coefficient of permeability of ground for numerical analysis and 3D indoor model experiment; ground water hydrodynamic model of YuanLiangShan tunnel was obtained through further thrashing out. and at last, 3D indoor model experiment, formulas of theoretical calculate ^ equivalent continuum model and numerical method were used to analyze the distribution of tunnel seepage field, and rule of water pressure distribution. Finally, we apply these results to the engineering practice.4 > Using numerical method to investigate the ultimate water-bearing capacity of standard cross section of single-track railway tunnel, further to optimize tunnel shape of YuanLiangShan tunnel among five possible shapes.5> Using numerical method to investigate the characteristics of ground stability and structural stress due to water press acting upon tunnel lininiz equally or unequally and local inflow water press.Results:1 ^ The concept of hydraulic pressure action coefficient was put forward. Rule of hydraulic pressure distribution at outer surface of grouted ring and lining back was obtained by combined numerical analysis, theoretical deduction and indoor model experiment, so that the value of water pressure was determined; the relationship between water pressure action coefficient and coefficient of permeability and thickness of surrounding rock, grouted ring and lining, controlled drainage volume was also obtained.2, Based on the case project of YuanLiangShan tunnel, the engineering application of rule of water pressure distribution obtained by indoor model experiment and numerical analysis is demonstrated.3n High hydraulic pressure threshold of standard cross-section lining style of single-track railway tunnel was determined, 0.40MPa. Egg-shaped or circular-shaped cross section is the rational choice in case of high-hydraulic pressure by optimized analysis; circular-shaped cross section is more competent when it exceeds 1.5MPa.4n Displacement, plastic zone, inner force and distribution characteristics was analyzed in case of equal, unequal hydraulic pressure and local inflow water press acting upon lining respectively; Envelope method determining the maximum bending moment of lining was put forward by borrowing theory of bending moment influence line when the water inflow location is not defined.
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