Deformation Of High-speed Railway Subgrade In Jacking Box Culvert And Its Control

Since the reform and opening up,China has witnessed a rapid economic development.Material flow and personnel flow are becoming busier and busier.Railway and highway transportation has always been a priority to traffic industry in our country.But a large number of railway and highway crossings have brought problems to traffic and cause traffic jams.Therefore,many crossings have been changed to interchange construction with the method of box culvert traversing under existed railway in order to solve the traffic jams and the traffic security problems.This paper aims to analyses the numerical simulation of the construction process considering the highway through the Beijing-Kowloon Railway,in order to study the effect of construction process of railway roadbed and its control measures.A three-dimensional model is established by using a piece of finite difference software F1AC3D.Simulation analyzes the deformation of existing line subgrade under different conditions under the culvert during construction.The simulation results show that:(1)During the excavation stage of working pit,when the excavation is more than a certain depth,the existing line subgrade deformation is large,it will affect the safe operation of the train;the impacts of train at different speeds on existing railway subgrade is relatively small,namely the working pit depth is a major factor of the line of subgrade deformation.(2)In the box culvert jacking stage,the jacking step and train’s speed are greater impacts on the subgrade deformation,especially in the jacking to the existing subgrade slope,subgrade deformation develops rapidly.In order to ensure the safe operation of trains,jacking step should not be too large,and the safety running speed of train can increase with the decrease of the jacking step.(3)After the soil grouting reinforcement around the box culvert,the effect of the jacking construction on existing railway subgrade deformation range and subgrade settlement decreases.Especially in the railway subgrade with grouting reinforcement,settlement decreases obviously,which has a positive effect on improving the safe operation of the train under constructionIn short,in the progress of construction,we need to strengthen the settlement observation at the stage of pit excavation and the early stage of traversing.And it is safe and reasonable when the train speed is controled less than 45 km/h with the step-length controled less than 2m.In theory,we can increase the speed of the train to improve the efficiency of railway operation when the soil around the box culvert is reinforced by grouting.