Effect Of Shield Tunnel Excavation And Compensation Grouting On The Surface Settlement And The Surrounding Soil Disturbance

As China's urbanization process carried forward,large cities generally take the subway construction and operation as the effective measures to solve the traffic congestion.Because of urban underground engineering constructions are founded in a densely populated and complex area,it is necessary to effectively control the influence of the subway tunnel construction on the surrounding environment.Shield method as at present the mainly applied method in subway tunnel construction,is the main research object of this article.We investigate the influence of tunnel excavation and compensation grouting on soil stress change s and surface settlement with numerical simulation and a set of sand model test platform which effectively simulated the process oftunnel excavation and compensation grouting.Researching both the general rule of surface settlement and uplift considering the influence of tunnel burial depthand the soil stress changes,we focus on the key influence factors and summarize the rules.The test data indicated that the surface settlement caused by tunnel excavation can be effectively predicted by Peck formula and the maximum settlement value was proportional to the volume loss.Additional volume compensation grouting is needed to uplift the ground surface as the effect of compensation grouting within the normal volume range is comparatively limited,meanwhile,the maximumsurface upheaval caused by additionalvolume compensation grouting showed a roughly linear relationship with the compensation groutingvolume.For various burial depth,the surface settlement range and settlement value differs from each other,and the effect of uplifting the ground surface is affected by the tunnel burial depth that the surface uplifting value decreases and the surface uplifting range expands with the increasing of tunnel depth,meanwhile the range difference caused by tunnel depth reduced with the increase of compensation groutingvolume.Duringthestageof tunnel excavation,the soil can be divided into three zones corresponding to the stress changes,i.e.,the positive archingzone,the unloading zone and the plastic zone which developed upward graduallywith the increase of volume loss.While during the stage of compensation grouting,the soil can be divided into two zones according to the stress changes,i.e.,the effective upheaval zone and the arching compensation zone.Along with the compensation grouting,the effective upheaval zoneand arching compensation zone gradually extends upward to the ground surface.Two-dimensional finite element analysis considering small-strain behavior of the soilwas carried out toreproduce the test data,the simulation results corresponded well with the experimental data,helping to further validate the disturbance mechanism by both tunneling and grouting revealed by model tests.