Layered Rock Tunnel Support Design Optimization Based On Numericalanalysis Of The Invert

China has a vast,complex geological structure,which has a layered structure of sedimentary rocks accounted for 77.3 percent of China's land area,and accounted for 66.6percent of the world's land area.Depending on the tilt angle of the rock,which can be divided into dipping,steep,steep and erect four layered intrusions.Because of this remarkable rock characteristic layered structure,leading to its structural deformation and strength properties also have significant anisotropy,the failure mode and mechanism of layered rock mass is significantly different from other rock.In addition,in the construction field often encounter a lot of layered rock mass stability related issues.Therefore,the study of the stability of layered rock tunnel excavation and other issues is particularly important.Based on the theoretical research,using the numerical simulation method of FLAC3 D to analysis stability and supporting effect of IV1 two-lane tunnel,which has different thickness horizontal layered surrounding rock at the bottom.Establishing flat model,invert model and bottom plus grouting anchor model,the total thickness of each model are 1meters,2 meters and 5 meters,each thickness divided into 0.5 meter per layer and 0.25 meter per layer.Analyze each model's rock stress,displacement,force characteristics of initial support,bolt axial force,plastic zone size and variation of the second lining.The analysis shows that:(1)According to numerical simulation of the three different thicknesses horizontal layered rock tunnel,the bottom displacement of invert model is the smallest,bottom plus grouting anchor model follows by,but the difference between them are controlled within10%.(2)The bottom plus grouting anchor model is slightly better than the invert model in control stress,plastic zone size,bolt axial force and secondary lining aspects.(3)By analyzing the different thickness IV1 two-lane tunnel in horizontal layered surrounding rock stability and supporting results,we can use bottom plus grouting anchor model replace invert model on the basis of consideration of the actual project.