Impact of Advance Pilot Tunnel Excavation in High-stress Soft Rock Tunnels on the Main Tunnel:A Case Study of the Yulong Snow Mountain Tunnel Project
In order to investigate the impact of advance pilot tunnel excavation in high-stress soft rock tunneling projects on the main tunnel,this study leveraged the Yulong Snow Mountain Tunnel project.Utilizing long-term field monitoring data and employing a numerical analysis model based on the finite difference program FLAC3D,the study examined the influence of advance pilot tunnel excavation on the stress of surrounding rock,rock displacement,and the distribution of plastic zones in the main tunnel,and the optimal spacing between the main hole and the horizontal guide was determined.The research findings reveal that during the excavation of the main tunnel,when the distance between the tunnel face and the monitoring section is 3.63 times the width of the main tunnel,the crown settlement,upper convergence,middle convergence,and lower convergence values at the monitoring section account for over 80％of the final deformation.After the deformation of the surrounding rock stabilizes,both upper and middle convergence values surpass the crown settlement.Advanced excavation of parallel pilot tunnels can effectively weaken the stress environment of the main tunnel.When the distance between the main tunnel and the parallel pilot tunnel is relatively large,the weakening in the surrounding rock stress is less pronounced.As the distance between them gradually decreases,the weakening in surrounding rock stress becomes increasingly significant.However,if the distance between the main tunnel and the parallel pilot tunnel is too small,the plastic zones generated by both excavations may intersect.Taking all factors into account,it is determined that the most optimal spacing between the main tunnel and the parallel pilot tunnel is 3.5 times the width of the parallel pilot tunnel.The crown settlement and invert uplift values of the main tunnel increase as the distance between the main tunnel and the parallel drifts decreases.The horizontal displacements of the left and right arch waists firstly decrease and then increase as the distance between the main tunnel and the parallel pilot tunnel decreases.
stress releaseoptimal horizontal distanceadvanced pilot tunnelplastic zonefield monitoring
万方数据
维普
