Response Law Of Train Vibration To Pore Water Pressure In Curved Tunnel Soil Layer

Due to centrifugal effects,metro tunnels located in small curve sections of chalky sand layers are more sensitive to the response of horizontal and vertical cyclic loads during train operation,and the long-term operation of the metro in this state can leave greater safety hazards as a result.In Zhengzhou,where silt is the main geological component,how to better control and predict tunnel deformation and soil liquefaction in small radius curved sections,and ensure safe and normal train operation in a timely and effective manner has become an important issue to be addressed during the construction and maintenance of the metro.This paper takes a small curve radius section of a metro shield interval as the engineering background,carries out long-term monitoring of the surrounding soil pore water and groundwater level,and uses Midas finite element calculation platform to establish a metro bed-lining-soil coupled dynamic model for mutual verification,to study the pore water pressure response law of the tunnel subsurface soil under the vibration load of the train in this zone,and to discriminate the liquefaction of the powder sand soil around the tunnel The main research elements are as follows The main research elements of this paper are as follows.(1)Through on-site monitoring of the soil in the subsurface layer of the curved shield tunnel under cyclic train loading in the chalk sand soil layer during metro operation,it is found that the pore pressure and super-pore pressure generated at the beginning of train vibration is not easily dissipated and transferred making it larger at the beginning of train operation,and the pore pressure may cause a small increase due to the peak commuting period,seasonal climate,and the influence of the water table,but the overall trend is a decrease due to the Powder fine sand soil particles fine presence of a small amount of clay particles,so that the soil layer has a certain strength and cohesion,with the train vibration pore pressure and super pore pressure in the late gradually stable.(2)A coupled bed-lining-soil dynamic model of an underground shield interval curved tunnel was established and cross-validated with the field measured pore water pressure results to further investigate the response law of train vibration on the excess pore water pressure along the vertical and horizontal directions in the powder sand soil layer around the curved tunnel.(3)By adjusting the tunnel burial depth,the number of running vehicles and the tunnel type in the calculation model,the pore water response law of the soil around the tunnel under train vibration loading was investigated,and a preliminary judgement on the liquefaction of the soil around the tunnel was made using theoretical analysis regarding the change in pore water pressure.Due to the superimposed load effect,the pore water pressure rises at a greater rate when two-way traffic meets than when a single train is running,and the tunnel depth is proportional to the pore water pressure at a certain water table.