Study On Blasting Construction Control Technology Of Shallow-buried Long-span Tunnel Near Existing Buildings

In recent years,with the rapid development of urban traffic engineering in China,the construction of urban tunnels is increasing,and the tunnel section is also growing.More and more complex construction conditions,such as the three-dimensional intersection of tunnels and existing roads,shallow burial and underpass residential areas,have brought new opportunities and challenges to the tunnel blasting construction.Therefore,the negative impact of controlled blasting on the surrounding environment and buildings(structures)has been brought about.More and more attention has been paid to noise.How to reduce vibration and blasting has become a technical difficulty in tunnel construction.Qixianling Tunnel,the first tender section of the West Extension Line of Southern Binhai Avenue,constructed by China Railway Ninth Bureau Group Fifth Engineering Co.,Ltd.,is close to Hongdu Fengjing District,Diaoyu State Guest House,Merchants Lanxi Valley District and crossing Qixian Middle Road.The construction conditions are complex,with a minimum horizontal distance of only 5 meters.In order to ensure the smooth completion of the tunnel project,the key technical problems of tunnel group construction are studied.The main work and research results are as follows:(1)In order to study the influence of construction on adjacent structures,the geotechnical finite element software Midas/GTS NX is used to simulate the excavation of tunnel construction,and the applicability of three construction methods in the project is explored,i.e.full-section method,step method and double-sided guide pit method.Based on the numerical simulation analysis,considering the influence of tunnel construction on the settlement of surrounding buildings,the tunnel span is large and the surrounding rock grade is relatively poor,and the drilling and blasting method is adopted to construct the left and right tunnels,and the step method is recommended to construct the left and right tunnels.(2)By using the time-history load curve calculation theory considering millisecond blasting and the finite element software Midas/GTS NX,a blasting model was established to compare and analyze the three-step blasting method and the zonal space extension blasting technology.Comparing the velocity and acceleration,displacement nephogram and shear stress and strain of buildings caused by blasting of two schemes,it shows that the vibration response of buildings caused by zonal space-extension blasting is less than that caused by three-step blasting,and the damage of three-step blasting is more obvious to buildings.Therefore,the use of zonal space extension blasting technology can reduce the impact of blasting buildings in tunnels,and achieve rapid and efficient construction of tunnels.(3)Based on the monitoring and back analysis of blasting vibration in site,it is suggested to adopt the blasting construction method of compound wedge cut subarea combination initiation network to control blasting.It can effectively reduce blasting vibration,ensure the safety and stability of buildings in Hongdu Fengjing District,and reduce the impact on residents.This construction method has fundamentally solved the problem of blasting construction in neighboring residential areas.After construction,all technical indicators meet the construction requirements.It has accumulated valuable experience for the construction of adjacent existing buildings in the future,and achieved obvious safety and economic results.