Optimize Of Construction Scheme And Security Assessment Of Cross Railway Tunnel

This article combined with the new Beijing-Zhangjiakou Railway tunnel under the existing Tang-hu heavy railway tunnel project.We mainly study the stability of tunnel surrounding rock under the influence of construction disturbance under the action of upper train load and blasting vibration.Based on the measured data of theoretical computer field,the displacement of surrounding rock in cross tunnel can be monitored in real time.At the same time,based on the monitoring data,the mechanical behavior of the surrounding rock of the tunnel can be roughly predicted.In the first line of the tunnel construction,I collected blasting vibration velocity of surrounding rock lining structures under construction tunnels and existing tunnels,optimized blasting construction schemes and support methods.The field test data show that the optimized construction scheme can help to reduce the negative impact of blasting vibration on existing tunnels and new tunnels.The optimized support scheme can effectively reduce the radial displacement of tunnels in the upper and lower tunnels.Based on the finite difference method numerical simulation analysis,the dynamic response of the cross-tunnel construction section when the heavy-empty train model passes is systematically studied.The results show that heavy-haul train loads can cause violent dynamic response of the surrounding rock near the cross-section of the tunnel.So the actual construction process should focus on this part of the support and blasting construction vibration.The main conclusions are as follows:1.Large sections of existing heavy-load railway tunnels occur at the upper and lower steps of the new high-speed rail tunnel,the left side of the middle step,and the left and right sides of the lower step.And the vertical settlement of the existing tunnel structure basically reached 85%?90% of the final value after the completion of the initial support of inflected arch;2.The numerical simulation results show that the dynamic characteristics(vertical displacement,vertical acceleration)of the underpass observation section also have obvious amplification effect compared with the ordinary observation section;3.Based on the field blasting vibration velocity data,the blasting parameters K and ? corresponding to different types of surrounding rocks in the newly built tunnel are obtained,and the maximum one-shot sound dose and the minimum control explosion safety distance for the surrounding rock grades of the lower section are Grade III,IV,and V.Three-stage blasting excavation proposed by engineering practice can effectively control the damage of blasting vibration;4.The proposed optimization plan for initial support construction can effectively reduce the displacement settlement of the newly-built high-speed rail tunnel and the existing heavy-load railway tunnel,which is conducive to the smooth passage of the lower-passage section.