Study Of Ground Deformation Caused By Underground Tunneling With Physical Model Test

Ground deformation during a tunnel construction is mostly caused by formation loss,it corresponds to the settlement when the tunnel is excavated(Shield movement).This paper first investigated the ground deformation during the construction of twin tunnels by applying the PECK formula,then introduces a physical model test which simulates the loss of formation caused by the construction of a tunnel by the drainage method,indeed the objective is to simulate the settlement of the formation caused by the loss of formation during tunnel construction and explore the laws of deformation under different rates of training loss.In the first section,from the monitoring data collected in the field during the digging of the first tunnel,PECK formula is used to obtain the deformation curve of the second tunnel by the symmetrical method.Finally,the superposition method was used to get the final curve.Analysis of the various curves obtained shows that the superposition method presents a larger deformation whose peak is located in the center of the tunnels.Therefore,this method is appropriate to predict deformations during the construction of twin tunnels.Furthermore,to better understand our study,in the experiment part,the process is as follows:first built a physical model then equipped it with a tunnel model,displacement sensors,and used the dried quartz sand to fill the box,and finally simulate this model by the drainage method.The results obtained at the end of simulation show that the direct factors affecting the formation sag are all related to the loss of the formation.In addition,the settlement of the surface and the interior of the formation increases with the increase in the loss of formation.The curve of settlement trough the formation is normally distributed,the range of surface sagging trough caused by the loss of the formation is about 3d and the width of the subsidence troughs inside the formation decreases with increasing depth.Moreover,the volume transfer rate of the formation settlement tank is defined,which is the ratio of the volume of the formation settlement tank to the loss of the formation,and the volume transfer rate of the formation settlement tank is inversely proportional to the formation depth,which is proportional to the rate of formation loss.Ground deformation is undesirable but also inevitable effect during subway tunnel construction;therefore,the best alternative would be to study the phenomenon to better understand the problem.Indeed,the study of this physical model was very instructive because it allowed us to well understand the concept of formation loss,to define ground deformation at model test different deformation rates and to deduce several settlement laws to predict the settlement during tunnel construction.