Research On Dynamic Response Law Of Tunnel Entrance Section Across Soft And Hard Rock Interface And Optimization Of Anti-vibration Measures

Based on the tunnel project of a certain line of the Central Asia Natural Gas Pipeline,this paper uses numerical simulation to study the dynamic response law of the tunnel entrance section across the soft and hard rock interface under the action of the0.6g peak ground motion acceleration,and the influence range of the interface is carried out.Zoning,giving anti-vibration measures for different sections.The main research contents and conclusions of this paper are as follows:(1)Study the dynamic response of the tunnel under the four working conditions of30°,45°,60° and 75° at the interface of soft and hard rock;the dynamic response of the tunnel structure in the soft rock section under the action of 0.6g ground motion It is more intense than in the hard rock section.Under different interface inclination angles,monitoring indicators such as relative displacement,equivalent stress and bending moment of the third strength theory decrease with the increase of the inclination angle of the soft and hard rock interface,and there are sharp changes at the interface and its vicinity.The peak and maximum values are mainly concentrated near the interface.(2)The dynamic response law of the tunnel between the soft and hard rock interface and the entrance is 10 m,20m,30 m and 40 m under four working conditions;in the longitudinal direction of the tunnel,as the distance between the interface and the entrance increases,the calculated the relative displacement,the equivalent stress and the peak value of the bending moment of the third strength theory decrease as the distance between the interface and the opening increases;in the direction of the tunnel cross section,when crossing the soft and hard rock interface,the arch foot and arch shoulder are the most stressed unfavorable location.(3)According to the working conditions of 10 m,20m,30 m and 40 m between the interface and the entrance of the tunnel,the corresponding stress and bending moment of the third strength theory are used as indicators,and the tunnel is divided into sections in the longitudinal and transverse directions,and optimized anti-vibration reduction is given measures.