Study On Large Deformation Control Technology Of Soft Rock Tunnel

China has begun to build a large number of expressway tunnels.In the practice of a large number of soft rock tunnels,many problems of large deformation of surrounding rock have gradually emerged.For example,the initial deformation is too large,the surface of the initial branch structure is cracked,the face is collapsed,and the second liner is cracked.These large deformation disasters are places where key control is required during the excavation of soft rock tunnels.Therefore,effective support measures are needed to prevent the occurrence of such large deformation disasters.Taking the gorgeous high-speed Wenbishan tunnel project as an example,this paper uses the field investigation,theoretical analysis,on-site monitoring and numerical simulation to study the large deformation control technology of the tunnel.The main research methods and their results are as follows:1.Survey the engineering geological conditions around the surrounding rock of Wenbishan Tunnel.The dome settlement and horizontal convergence values of the typical three sections of the tunnel are monitored.The monitoring results show that the total displacement values of the dome settlement and horizontal convergence are beyond the normal range.2.According to the monitoring results of typical three sections and the observation of the construction site,the large deformation characteristics of the tunnel are summarized: the cumulative displacement value is large,the deformation rate is fast,and the initial branch structure is excessively deformed and curved.3.The construction method and support measures for the large deformation tunnel of weak broken surrounding rock are discussed.On the basis of referring to the large deformation control technology of the domestic soft rock tunnel,it is determined that the excavation method of the Wenbishan tunnel is the core excavation method,and the initial support method is the joint support of the anchor spray net.4.Using the Midas finite element software to numerically simulate and optimize the excavation sequence and support parameters of the tunnel construction method,and compare and analyze the support parameters used at the construction site.Determine the optimal value of the support parameters of the Wenbishan tunnel.