The Influence Of Bedding Plane On Opposite Through Construction Safety Of Long Tunnel

The rapid construction of long and large tunnels is an important technical issue for mountain tunnels.When designing and constructing large-buried tunnels with complex terrain and geomorphic environments,the butt-through plan of adding horizontal tunnels for the main tunnel is generally preferred to achieve the purpose of rapid construction.Under the condition of high ground stress layered surrounding rock,the relative geometric relationship between the construction direction and the bedding plane has a significant influence on the tunnel deformation and supporting force.In order to improve the safety of the butt-through construction,the influence of the inclination angle and direction of the bedding surface as the evaluation factors for the reasonable determination of the through-construction plan has important engineering practical significance.Based on the Yuelongmen Tunnel on the Chenglan Railway,this paper studies the influence of the bedding face on the construction safety in the connection of long and large tunnels.Using FLAC3 D finite difference software,a three-dimensional numerical simulation of the tunnel construction process under the condition of high ground stress layered surrounding rock is carried out.The direction of the bedding plane is perpendicular to the tunnel driving direction,the direction of the bedding plane is parallel to the tunnel driving direction and the inclination angle of the bedding plane is90 ° In the three cases,the tunnel deformation and supporting force during the tunnel construction process are compared and analyzed.The focus is on the analysis of the influence of different bedding plane inclination angles on tunnel deformation and supporting force when the bedding plane strikes perpendicular to the direction of tunnel excavation.Combining with the on-site construction conditions of the two steps of the butt-through section of the right line of the Yuelongmen Tunnel,through threedimensional numerical simulation calculations,a butt-through plan that is conducive to improving the safety of tunnel construction is proposed.The main results are as follows:(1)When the direction of the bedding plane is perpendicular to the direction of tunnel excavation and the inclination angle is different,the influence of the bedding plane is mainly reflected in the vault area and the arch bottom area of the tunnel,and has little effect on the left and right side walls of the tunnel.And when excavating in reverse layer,the influence of bedding on the arch bottom is greater than that of the arch top;when excavating along the layer,the influence of bedding on the arch top is greater than that of the arch bottom.When the bedding surface is gently inclined(the inclination angle is 0-30°),the change of the inclination angle has a very obvious effect on the settlement of the dome and the uplift of the arch bottom;when the inclination angle of the bedding surface is greater than 30°,the influence is slight;when the bedding surface is inclined When the inclination angle exceeds 70°(the bedding surface is steep),there is basically no effect.(2)When the direction of the bedding plane is parallel to the direction of tunnel excavation and the inclination angle is different,the deformation of the hollow section of the tunnel shows obvious asymmetry.The maximum inner space convergence does not change with the change of the bedding surface inclination,but the maximum inner space convergence direction varies with the bedding The face inclination angle changes and is perpendicular to the bedding surface.(3)When the inclination angle of the bedding plane is 90° and the direction is different from the direction of tunneling,the influence of the bedding is mainly reflected in the left and right arch areas of the tunnel,and basically has no effect on the tunnel vault area and the arch bottom area.When the direction of the bedding plane intersects with the direction of tunnel driving at a small angle(stroke is 0-30°),the direction of the bedding plane has a significant impact on the left and right arch waist;when the direction of the bedding plane and the direction of tunnel driving are at an angle greater than At 30°,the impact is slight;when the direction of the bedding plane intersects with the tunneling direction at a large angle(stroke is 70-90°),there is basically no effect.(4)When the bedding plane of the layered surrounding rock is perpendicular to the direction of tunnel excavation,when two steps are used for butt-through construction,the inclination of the bedding plane has a much greater impact on the arch bottom uplift than on the arch top settlement.In addition,during bedding excavation,due to the existence of the bedding surface,the arch top within 0.5 times the hole diameter and the arch bottom within 1 times the hole diameter from the side of the stop construction to the through surface will have obvious disturbing effects during the penetration process.;During the excavation of the reverse layer,due to the existence of bedding,the arch top within the range of 1 times the hole diameter and the arch bottom within 0.5 times the hole diameter from the side where the construction is stopped will be obviously disturbed during the penetration process;In addition,the excavation on the side of the continuous construction has a significant degree of disturbance on the side where the construction is stopped,and the amount of disturbance decreases with the increase of the inclination of the bedding surface,that is,the degree of disturbance on the side where the construction is stopped in the gently inclined rock formation is greater than that of the steeply inclined rock formation..During the buttthrough construction of long and large tunnels in layered surrounding rock,priority should be given to the butt-through connection in the direction of the layer,and the support on the side where the construction is stopped needs to be reinforced.