Study Of The Key Technology Of The Blast-control During The Subway Excavation Under The Complex Environment In Urban Areas

With the development of a large number of traffic facilities in our country,urban subway project gradually increased in recent years.Constrained by geological conditions,many subway projects need to be excavated by drilling and blasting.However,most of the subway project is located in the prosperous zone with a dense population and dense surface buildings as will as complex environment.The vibration effect caused by blasting may endanger the safety of surrounding buildings,which brings more strict requirements to the blasting construction and makes the construction of the blasting more difficult.Accordingly,it has become a major subject in the field of blasting engineering that research on the propagation characteristics and attenuation rule of blasting vibration wave in the process of blasting excavation of the city subway and prediction and control effect on buildings by blasting vibration with taking reasonable measures of reducing vibration.Taking the subway station of Guangzhou Metro Line 13 from Xia-yuan station to Nan-gang station as background and based on the theory and method of blasting vibration,the paper uses Dynamic finite element programming ANSYS/LS-DYNA to establish three dimensional model of tunnel which carries out numerical simulation with two kinds of blasting excavation of conventional blasting and hydraulic blasting during blasting excavation process.The propagation characteristics and attenuation rule of blasting vibration wave in surface,blasting center and stratum in different blasting methods are compared and analyzed.Finally chooses blasting method with small vibration effect;More reasonable judgment of surface vibration speed is determined by comparing effect by blasting vibration on excavated surface and unexcavated surface of tunnel and analyzing whether the cavity formed by the tunnel excavation has amplification effect on the surface blasting vibration velocity.Then hydraulic blasting has been optimized and analyzed from charge structure and the vibration effect of blasting method in four different charge structures is simulated.It determines optimal charge structure of hydraulic blasting by comparing and analyzingsurface vibration velocity,lining vibration velocity and lining stress of hydraulic blasting in four different methods.Finally the regression analysis is used to analyze monitoring data of blasting vibration and it comes to Sadaovsk formular that effects the blasting vibration intensity.Based on the basic theory,control theory and engineering characteristics of controlled blasting,blasting control measures are put forward and a detailed plan of tunnel blasting construction is developed according to the content of tunnel excavation.This not only ensures the smooth blasting construction,but also provides technical reference for similar projects.