| With the traffic jam problem becoming more and more serious,the subway construction has been developed unprecedently.With the need of urban planning,metro lines often cross phenomenon exists,so new subway foundation pit adjacent existing tunnel deformation caused by the construction problems get the wide attention from engineering,although a large number of scholars have carried on the thorough research for the problem,but the uniqueness of the foundation pit engineering has a strong,soil differences directly affect the results.Silt has the characteristics of poor stability and good permeability and so on.When the nearby tunnel has a large deformation,it is easy to cause water seepage and other disasters.Therefore,it is necessary to study the influence of foundation pit construction on the nearby operating tunnel deformation.Based on a subway station in hangzhou,the deformation of adjacent tunnel caused by foundation pit construction is measured and analyzed in the whole process.HSS model parameters of silty soil were obtained by experiments,and the deformation law of adjacent tunnel under different excavation methods and horizontal distance of tunnel in foundation pit was studied by finite element method.The main work and conclusions of this paper are as follows:（1）Nine parameters in the HSS model were obtained through standard consolidation test,triaxial consolidation drainage shear test,triaxial consolidation drainage loading,unloading and reloading test,and resonance column test.The reference tangent modulus Eoereof silty HSS is 17.9Mpa,the secant modulus E50re f is18.9Mpa,the failure ratio fR is 0.97,c￠is 1.1k Pa,j￠is 28.5°,the static side pressure coefficient k0 is 0.52,the unloading and reloading modulus Euris 50.7mpa,0Gre f is 0.7 times 0G.The corresponding modulus of hangzhou silty clay,and 3 kinds of modulus Eoere df、E50re f、Euris larger than that of silty clay.The value of hangzhou silt 0Grefobtained by empirical formula is far less than the experimental value.（2）The deformation of adjacent tunnel under the construction of TRD,triaxial cement mixing pile and underground continuous wall is measured and analyzed.The results show that the effective earth pressure on the left side of the tunnel is greater than the effective earth pressure on the right side of the tunnel,and the effective earth pressure on the lower part of the tunnel is greater than the effective earth pressure on the upper part of the tunnel.In the construction stage of the three-axis mixing pile,the soil displacement under the tunnel is limited due to the role of TRD as a barrier.During the construction of the underground continuous wall,the effective earth pressure on the upper and lower sides of the tunnel forms a pair of balancing forces,which ensures that the clearance height of the tunnel is almost unchanged.However,the depth of the underground continuous wall is large,and the unloading effect is obvious,which makes the soil under the tunnel move into the groove,resulting in the micro-settlement of the tunnel.（3）Based on the measured analysis of the surrounding deformation caused by the excavation of the foundation pit,it is found that the horizontal displacement of the underground continuous wall does not always occur in the same direction,and the cumulative horizontal displacement of the underground continuous wall presents an approximate"S"type from top to bottom.The surface subsidence at different distances perpendicular to the direction of the envelope structure approximates the"concave"deformation pattern.The excavation of foundation pit will cause the wall top to heave and deform.The deformation increment of different monitoring items in different construction stages is not the same.（4）On the basis of the basic agreement between the measured values and the numerical simulation results,the numerical analysis results show that the pit excavation method can more effectively control the influence of pit excavation on the deformation of adjacent operating tunnels than the parallel excavation method;The maximum ground settlement point does not change with the change of the horizontal distance between the foundation pit and the tunnel,and the maximum horizontal displacement of the tunnel decreases with the increase of the horizontal distance between the foundation pit and the tunnel.Therefore,in order to control deformation within the strong influence area,protective measures are one thing,and the distance between the foundation pit and the tunnel can be controlled. |
