Study On Stability Of Surrounding Rock In Tilted And Counter-tilted Layered Tunnel

Due to the anisotropy of its structure and the complex and varied failure modes of the widely existing layered rock masses,the stabilization of the surrounding rock’ stability in the geological body is always a challenge for geotechnical engineering.Research is also an important topic of concern in the academic community.In this paper,a tunnel model of layered rock mass structure is established.The finite-difference method was used to simulate the stability of the surrounding rock of the tunnel entrance section(tilted excavation)and the exit section(counter-titled excavation)and the optimization design study of the anchorage support angle.Because the related literature focuses on the stability and failure modes of the beveled and anti-titled slope of the layered rock mass,or the stability of the surrounding rock of the tunnel when the excavated tunnel is parallel to the rock strata and has nothing to do with the trend.In the research of protection,this paper analyzes the stability of the surrounding rock when the excavation tunnel axis is perpendicular to the rock strata from another perspective.(1)Definition: When the direction of tunnel excavation coincides with the direction of rock formation inclination,it is inclined excavation,on the contrary,it is counter-tilted.The mechanical model can use the cantilever composite beam.For the tunnel vault in the same buried depth,the shear strength is greater than that in the reverse excavation.At the same level,the CIS inclined excavation is more prone to shear slip along the surface than the reverse excavation.The time of this calculation,while past indicates that the unit was.(2)The finite difference method was used for numerical simulation to obtain the stress field,displacement field and plasticity of each section.The results of the simulation of the area and the analysis of the stress concentration of the tunnel face rock facing the tunnel in the excavation at the time of excavation.The extent,displacement deformation,and plastic zone range are all greater than those for anti-tilted excavation tunnel,and the distance between the two tunnel design lines is 22 m,that is,the net distance between the two tunnels is not less than 1.0D,so between the two tunnels,the plastic zone of the rock has not yet penetrated,and the influence between the two tunnels is small.(3)From the field monitoring data,it can be concluded that the deformation of the surrounding rock in the tilted excavation section is larger than that in the countrer-tilted section.The deformation of surrounding rock has undergone several stages of rapid development,gradual slowdown,and basic stability.No matter what excavation direction,there is no significant increase in the deformation of surrounding rock at about 2 to 2.84 times the diameter behind the tunnel face.(4)According to the deformation characteristics of tunnel surrounding rock of Dongqiao Tunnel in the inclined excavation section,the optimization design study of the angle of bolt support was conducted to numerically simulate and analyze the tunnel surrounding rock and initial lining displacements and anchors under various optimization schemes.The situation of stress shows: When the angle of the bolt is different,it has a great influence on the displacement and stress of surrounding rock caused by excavation.When the azimuth orientation is in tilted side,and the angle is perpendicular to the rock layer,the anchorage effect of the rock layer method is the best,and then is the vertical anchor,the worse of anchorage effect is that bolts hit in counter-tilted side of azimuth orientation and deviates from the direction of the vertical rock.