Study On Pivotal Techniques Of Neighborhood Tunnel In Complicated Environment

With the fast development of the national economy, many railway and highway tunnels should be built. However, due to the short clear distance between a new tunnel and the existing one, excavation and blast in the new tunnel will influence on the security of the existing one in a certain degree. On the another hand, it's harmful for the safety of various adjacent buildings to construct new tunnels in under-cross them in urban. Generally, there are many disadvantages, just like complex or unfavorable geological conditions in tunnel construction. They will lead to blind tunneling and safety incipient faults if they aren't discovered in time. Take Jiaojinshan tunnel in Dalian for example, due to the complicated conditions, there are lots of difficulties during construction. For a shallow-buried small-spaced tunnel with various unfavorable geological conditions and difficulties, the main problem is how to keep the existing tunnel in normal operating state in under-crossing buildings. In this paper, based on mass of field tests, monitoring data and theoretical calculation, the technology of controlled blasting is generalized and experienced. The influence and selecting principles of the blasting parameters such as powder species,blasting drilling scheme and detonating circuit, etc. are mainly discussed. According to the analysis and regressive calculation conducted on blasting monitoring data, it is proposed that the blasting construction should be executed combining with blasting monitoring, and it is feasible and necessary to adjust the blasting scheme in time according to the monitoring data. Besides, the excavation deformation, blasting vibration and economic performance should be considered during tunneling technology optimizing. The application of geological radar adopted in geological forecast is discussed, coming to a conclusion that the risk of blind tunneling can be effectively avoid by using geological radar. Finally, the application of geological radar adopted in detecting the flattening between initial support and surrounding rock and secondary support thickness in order to control quality is formulated in detail.