Research On The Law Of Soil Settlement Caused By Ground Loss In The Condition Of Compound Stratum

As the process of urbanization continues to accelerate,more and more cities have begun to build subways,and the stratum loss caused during the construction of subway tunnels often leads to the settlement of the upper soil,causing various major accidents such as surface collapse.At present,domestic and foreign scholars have made remarkable achievements in the study of the surface subsidence law of homogeneous layers caused by formation loss.However,the research on the subsidence law of composite strata and the interior of the formation is not in-depth.This article combines indoor model tests and numerical simulations.The method is to study the law of soil settlement caused by formation loss under the conditions of homogeneous layer and composite layer.The main research contents and results are as follows:(1)A complete indoor model test system has been developed,which mainly includes an indoor model test box,a tunnel model,and a displacement monitoring system.(2)Through the study of model test and numerical simulation,the maximum surface settlement under homogeneous layer conditions is at the central axis of the tunnel.The width coefficient of the surface settlement groove increases with the increase of the stratum loss rate,and the width coefficient of the sand settlement groove is about It is 2 times the tunnel diameter,and the width coefficient of the surface settlement trough in the fine-grained soil layer is about 3 times the tunnel diameter.In the interior of the stratum,the settlement deformation at different depths all conform to the Gaussian normal distribution.The width coefficient of settlement trough i in sandy soil layer and fine-grained soil layer increases with the increase of the depth h from the transverse axis of the tunnel,and decreases with the increase of the friction angle in the formation.The width coefficient of the surface settlement trough is the largest.The volume of the settlement tank increases from bottom to top.The volume transfer rate of the settlement tank is related to the soil quality.The looser the soil,the greater the volume transfer rate of the settlement tank,the deeper the formation depth,and the volume of the settlement tank under different formation loss rates.The more concentrated the transfer rate.(3)On the surface of the composite strata,the surface subsidence at the central axis of the tunnel is the largest,the width of the ground subsidence is about 5 times the tunnel diameter,and the width coefficient of the ground subsidence trough is smaller than that of the homogeneous strata.In terms of the interior of the formation,the maximum settlement of the formation under the condition of the composite formation is higher than that of the fine-grained soil layer,and the difference between the maximum settlement of the sandy soil layer is slightly smaller.The width coefficient i of the composite stratum settlement trough increases with the increase of the depth h from the transverse axis of the tunnel.The volume of the settlement trough increases from bottom to top.The volume transfer rate of the stratum settlement trough is more stable than that of the homogeneous layer.