Analysis Of Subway Train Vibration Response In Sand Stratum

With the rapid development of Metro in big cities,the environmental problems caused by Metro vibration are gradually concerned by people.This paper takes Shijiazhuang Metro Line 2 as the background to study the propagation law of subway train vibration in sandy soil foundation and the liquefaction problems that may occur under the vibration load of subway train.Because liquefaction may lead to uneven settlement or structural damage of tunnel structures or existing buildings around them,which may endanger the safe operation of Metro trains,the relevant research in this paper has certain significance for the safe operation of trains.Through the comparative study of a large number of literatures,using the related research of predecessors,through the train-track coupling analytical model combined with the relevant parameters of Metro A vehicle,the time-history curve of the metro train vibration load is determined,which provides the source load for the subsequent research.The simulation method of solid-liquid coupling under dynamic load and the criterion of sand liquefaction are determined.Based on the sandy soil foundation in Shijiazhuang area,a three-dimensional solid-liquid coupling model is established by using the finite difference software FLAC3 D.The influence of underground water,the number of trains running,different stratum conditions,different burial depth and different subway running speed on the propagation law of train vibration in the stratum is studied.The liquefaction of the soil layer is preliminarily judged.Based on the actual working conditions of Shijiazhuang Metro Line 2,the dynamic response of the pile foundation of nearby bridges to the vibration of metro trains is studied.The time history curves of displacement,velocity and acceleration of pile foundation before and after the application of retaining piles are analyzed,and the influence of different tunnel depth on the settlement of pile foundation is analyzed.The variation of pore water pressure near pile foundation with train dynamic load is also discussed.The research contents in this paper have certain reference value for practical engineering,and the liquefaction mechanism of saturated sand layer caused by subway train vibration is preliminarily discussed.