| More than half of the completed tunnels in western of China are located in karst areas.Karst geology has brought many problems to the construction and operation of tunnels,among which karst water inrush is the most serious problem.The tunnels that have been completed and operated in China through the karst area are restricted by the design and construction technical conditions during the construction period.There are generally leakage diseases of the tunnel lining structure,and even the lining structure is damaged by local high water pressure.Based on Chongqing Tongxi Tunnel,this article aims at the problem of lining structural instability and failure under the action of local high water pressure during the operation of deep-buried karst tunnels.On the basis of onsite investigation and testing,it combines theoretical analysis,indoor model tests and numerical simulations And other methods,a systematic and in-depth study on the mechanical behavior and control technology of the lining structure of deep buried local pressure karst tunnels.The paper's main work and results are as follows:(1)According to the investigation of the hydraulic cracking of the lining structure of the Tongxi Tunnel and the on-site special test,the influencing factors of the hydraulic cracking of the lining structure of the Tongxi Tunnel were analyzed;on this basis,the deep buried partial pressure tunnel was revealed Disaster-causing conditions for lining failure.The research results show that the main influencing factors of karst tunnel lining hydraulic cracking are surrounding rock and groundwater factors,design and construction factors,and drainage and drainage design factors;the disaster conditions of deep local pressure tunnels are mainly vertical development of karst and high water content The energy storage of the structure and the stability of the rock wall of the karst cavity are weakened.(2)According to the tunnel structure calculation model,the principle of load structure method and the water pressure and rock stress superposition calculation law,it can establish the tunnel lining structure 's internal force calculation model under the action of local high water pressure.By solving the corresponding lining flexibility Degree coefficient,elastic resistance distribution and Mathematica software programming,iterative method is used to find the distribution law of internal force and displacement of tunnel lining structure under different local water pressure.(3)The similar model test device of tunnel lining structure stress has been built,which can simulate the local high water pressure;based on the similarity theory,a similar model test of the tunnel lining structure under different high water pressure action positions was carried out,and the local high water pressure was obtained.Under the action of pressure,the internal force changes at each characteristic point of the lining and the failure mode of the tunnel lining.(4)According to supporting engineering's three-dimensional numerical simulation analysis,the stress and deformation change of the tunnel structure for the deep-buried karst tunnel under the local high water pressure of the side wall is obtained,and compared with the model test and field investigation.(5)The stress and deformation characteristics of the tunnel structure were anlysized,when different local water pressures acted on the tunnel's arches.The stress and deformation change of the lining structure were obtained.Tt can be found that the lining structure's internal force and deformation are still symmetrically distributed under the effect of local water pressure at the arch of the tunnel.As the hydraulic load increases,the internal force of the lining gradually increases from the arch to both sides,reaching the maximum at the arch foot,but the internal force at the invert arch does not change much.The lining structure is squeezed and deformed inwards overall,and the sills and side walls on both sides are squeezed outwards,resulting in outwardly expanding deformation,in which the maximum horizontal displacement occurs at the two sides of the arch and the maximum vertical displacement occurs at the top.The internal force and deformation were greatly influent by the width of the hydraulic load.(6)The stress and deformation characteristics of the tunnel structure were anlysized,when different local water pressures acted on the left wall of the tunnel,and the stress and deformation change of the lining structure were obtained.The research results show that:under the effect of variable head height and different load widths on the left wall of the lining structure,the lining structure's internal force and deformation change from symmetrical distribution to small at the right side and large at the left side.The axial force gradually decreases from the left side wall to the left side arch waist and left side arch foot,while the bending moment appears positive bending moment maximum is the left side wall,the maximum negative bending moment is located at the left arch foot,with the water pressure When the value changes,the inflection point also changes;Horizontal displacement plays a leading role,the left side wall of structure's horizontal displacement is the largest,and the vertical displacement of the left wall to the left arch waist and the left wall to the left arch foot is large.The internal force and deformation of tunnel is greatly influent by the width of the hydraulic load.(7)According to the study on the water-repellent design of the supporting project,the design of the water-repellent design of the diseased section of the tunnel and the reinforcement design and treatment technology of the lining structure are proposed.Combining with the research results of the thesis,the principle of waterproofing and drainage of tunnels in local pressure karst section and the design method and treatment measures of lining structure when the karst tunnel passes through different karst conditions are proposed. |
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