Study On Disease Mechanism And Treatment Technology Of Uplift Deformation At The Bottom Of Operating Railway Tunnel With A High Water Pressure

In recent years,invert uplift diseases of railway tunnels operating in water-rich areas have occurred from time to time,resulting in track uplift,lining cracking and other operational diseases,seriously affecting operational safety.In this doctoral thesis,through the investigation of typical cases in water-rich area,it is found that the evolution process of those cases is about the same,which is related to the high water pressure at the bottom of the tunnel after rain,but the disease mechanism and treatment methods still need to be further clarified.To this end,based on seepage theory,this doctoral thesis obtains the theoretical model and characteristics of tunnel seepage field under the internal and external drainage system;through the analysis of 3D numerical simulation and the model test,the invert deformation mechanism and structural damage mechanism of tunnel with the internal drainage system in service environment are studied;through model test and numerical simulation,the characteristics of seepage field,displacement field,stress field and structural performance of the tunnel with the deep buried gutter drainage method are explored,and the recommended design values are proposed;the treatment process and measures of the invert heave disease are summarized,the prevention suggestions for the invert heave disease are proposed,and the treatment method is successfully applied to Malazhai tunnel of Shanghai-Kunming high-speed railway.The main conclusions of this doctoral thesis are as follows:(1)Through the investigation of 20 disease cases,the information of rock susceptibility,geological conditions,buried depth conditions,surface topography,rainfall conditions,disease characteristics and the influence of operation are analyzed,finally revealing the evolution mechanism of the disease in karst area or non-karst area cases considering surface rainfall and surface topography.Meanwhile,based on the control standard of rail geometry state under different running speeds,the key reason for the frequent occurrence of rail bulge diseases in railway tunnels in recent years can be clarified,that is,the design of the bottom structure of the train can not completely match the control requirements of rail shape and position of high-speed trains,thus creating the catastrophic trend of "small deformation but great harm".(2)Aiming at the internal and external drainage systems adopted in the water-rich tunnel,the theoretical model and analytical solution of the tunnel seepage field considering the action of grouting ring were derived based on the mirror image method and the theory of seepage mechanics.Based on the mirror image method and seepage mechanics theory,the theoretical model of tunnel seepage field under different drainage system was deduced according to different drainage systems adopted by water-rich tunnels,and the influence law of typical engineering parameters on tunnel drainage and external water pressure of structures was discussed,which is verified by analytical degradation,numerical simulation and field test methods.The superiority of external drainage mode in controlling inverted arch water pressure was clarified,and the influence of typical factors on tunnel discharge and external water pressure of structure was further discussed.In addition,the correctness of the analytical model was verified by analytical degradation,numerical simulation and field testing.(3)Combining 3D printing technology,a tunnel seepage model test method with visualization,quantification and refinement was proposed.Then,the characteristics of seepage field,deformation field and stress field as well as structural safety performance of a double-line railroad tunnel with design speed of 350 km/h using internal drainage method under service environment are investigated by combining model tests and numerical simulations.The research results showed that with the rise of the groundwater level,the water pressure at tunnel bottom by internal drainage method grows significantly,and the high water pressure at tunnel bottom triggers the bottom structure to produce "large in the middle and small at the ends" of the bulge deformation and a sharp increase in the internal force of the structure,which leads to the "water level in the ground 30～40m,water pressure at the bottom of the tunnel >300k Pa" when the track deformation exceeds the limit and affects the line traffic.If there was a blockage in the drainage system,especially if the blockage degree is more than 50%,it will further aggravate the severity of the disease.At the same time,when the track uplift exceeds 25～30mm,it will also be accompanied by the crack of the bottom structure.(4)For the combined internal and external drainage of the deep-buried ditch drainage system,the characteristics of seepage field,deformation field and stress field as well as structural performance of high water pressure railway tunnel under different service conditions and different design parameters were investigated through model tests and numerical simulations,and the recommended design parameters of "pipe diameter0.6-1.0 m,buried depth 0.2-0.5" were proposed.The research results show that with a new drainage channel at tunnel bottom,the seepage field of the bottom surrounding rock was dominated by the deep buried ditch,and because of the low drainage elevation and strong discharge capacity of the deep buried ditch,it can realize the effective control of the water pressure at tunnel bottom.The diameter parameter is the main influencing factor of the drainage efficiency of the deep buried ditch,with the increase of the diameter,the bottom structure disease was gradually improved and even eliminated.However,the bottom structure was basically stable after the diameter of the pipe > 0.8m,so there is no need to pursue excessive pipe diameter.If the tunnel drainage blind pipe was blocked,the drainage volume of the deep buried trench increased accordingly,which ensures that the stability of the bottom structure can still be maintained.The engineering application further verifies the obvious advantages of the deep buried ditch drainage system compared with the internal drainage system in controlling the water pressure of the tunnel invert and guaranteeing the stability of the tunnel and track structure.(5)The treatment process and principle of invert heave disease of railway tunnel are clarified,and the treatment measures of invert heave disease are systematically summarized.At the same time,according to the analysis results of invert heave disease of tunnel with internal drainage system,the prevention suggestions of railway tunnel bottom uplift problem are put forward.The disease treatment method has been successfully applied to Malazhai tunnel of Shanghai-Kunming high-speed railway.The on-site monitoring data show that even after the historical torrential rain,the tunnel structure can still ensure stable displacement and is basically not affected by surface rainfall,which verifies the effectiveness of the treatment scheme and can provide reference for similar disease cases.