Study On The Overall Stability And Anti-Floating Technology Of Fractured Rock Subway Station Under The Coupled Hydro–Mechanical Effect

With the completion and operation of subway tunnels and stations along the line,the seepage effect of groundwater is one of the inevitable factors to be considered.At present,for the anti-floating research of subway stations,the water pressure is usually equivalent to the concentrated force given to the floor.It is difficult to analyze the process of water seepage from the high-water pressure area to the station floor through the surrounding rock in the real project,and it is impossible to study the influence of different confined water area positions,water pressure in different areas and physicalmechanical properties of different fractured rocks on the floating of the floor.Based on the field project of the Nansanhuan Station of Xuzhou Metro Line 3,this thesis studies the influence of different anti-floating measures and different conditions of groundwater on the deformation and structural internal force of the fractured rock foundation station based on the hydro–mechanical coupling effect through literature analysis,theoretical derivation,comparative analysis,indoor test and numerical simulation.The main conclusions of this thesis are as follows:(1)Through theoretical derivation,the water seepage behavior model of subway station crossing water-rich surrounding rock and the deformation control equation of bedrock fractured rock in subway station are obtained.According to the coupling effect mechanism of the two,the time-space evolution constitutive model of stationsurrounding rock under hydro–mechanical coupling effect is established.(2)In order to obtain the physical and mechanical parameters of the surrounding rock of Nansanhuan station and verify the correctness of the proposed constitutive model,the indoor parameter test is carried out.The seepage test of surrounding rock samples is carried out by using the self-made micro multi-field coupling seepage system.The results show that under the condition of constant water pressure,the confining pressure is inversely proportional to the total displacement;under the condition of constant confining pressure,with the increase of water pressure,the greater the seepage velocity inside the rock mass,the faster the seepage tends to be stable,and the total displacement tends to be stable faster.(3)By compiling the constitutive model into COMSOL Multiphysics,the same working condition model as the published Liupanshan tunnel excavation wetland project and indoor seepage test is established to verify the constitutive model.The results show that the results obtained by the model in this thesis are in good agreement with the field data and test results,which verifies the correctness of the constitutive model in this thesis.(4)Using COMSOL Multiphysics,a two-dimensional universal model of surrounding rock is first established,and the evolution process of any position of surrounding rock under groundwater seepage under hydro–mechanical coupling is explored.Furthermore,a three-dimensional characteristic full-scale hydro–mechanical coupling model of the station-surrounding rock of the South Third Ring Station is established to explore the effects of different confined water areas,different water pressure,and different fractured rock characteristic parameters(permeability,porosity,etc.)on the water pressure,stress,and floating degree of the floor-station-surrounding rock under multi-field coupling effects.Three three-dimensional models of three typical anti-floating measures are established.Under the anchor bolt,the average stress of the station floor is reduced by 61.3%,the stress concentration of the floor is greatly weakened,and the maximum vertical displacement is reduced by 20.2%.The antifloating effect is the most significant compared with the composite wall method and the uplift pile method.The Study results of this thesis break through the theoretical bottleneck that the traditional engineering scale research method is difficult to analyze the influence of different confined water areas and fractured rock characteristics on the overall stationsurrounding rock,and provide a good theoretical basis and design guidance for the overall stability and anti-floating safety protection measures of subway stations crossing fractured rock under the action of groundwater in the future.This thesis has 91 pictures,7 tables,and 113 references.