Study On Controlled Blasting Technology Of Covered Rock Mass In Shield Tunnel

With the continuous development of subway engineering construction,the problems encountered in the construction process are endless.In the eastern seacoast,the subsection of shield tunneling is one of the biggest problems in shield construction.At present,there are obvious shortcomings in the treatment methods of solitary stone and bedrock.Therefore,a new step for shield construction technology is put forward by using drilling rig to drill directly on the ground and making special drug barrel to break the stone and rock in the composite stratum.In this paper,the theoretical analysis,numerical simulation and field measurement,the method of the shield tunnel hidden boulder and the bedrock of control blasting technology is studied,research results will provide theoretical guidance and application for practical engineering.The thesis obtains the following main results:(1)For the solitary rock and bedrock,with the increase of charge,the peak vibration velocity of the surface particle increases,and the maximum and average of the rock fragmentation degree decreases with the increase of the loading dose.(2)When the hole spacing and the charge is same,the interval of boulder crushing effect better charge.(3)When the interval between rows is 0.9m,the largest degree of fragmentation of solids is large,among which,when the continuous charge length is 1.4m,the largest degree of fragmentation of solids is the largest.When the interval is 1.1m,the maximum fragmentation degree of the stone is small.When the interval loading length is 1.7m,the maximum fragmentation degree of the stone is 18.065 cm.(4)When the detonation time difference between the two columns is 4ms and the gun hole spacing is 0.85 m,the maximum value and average value of bedrock fragmentation degree are the minimum;When the blasting started at the same time and the gun hole spacing was 0.95 m,the maximum and average value of the breaking degree of bedrock were the largest.When more than 70° slope Angle,slope will be the biggest broken rock blocks of more than 30 cm,the need to increase the grain in slopes.(5)The peak vibration velocities of the test points of lonely rock blasting are 2.2854cm/s and 2.1010cm/s respectively,which are smaller than the measured data and meet the requirements of blasting safety regulations.The results of field sampling and numerical analysis of blasting effect are close to each other.The peak vibration velocity of bedrock blasting test points was 2.5216cm/s and 2.5216cm/s respectively,slightly less than the measured data.The results of field sampling and numerical analysis are close to each other.(6)The use of micro-differential blasting,the existence of weak face and the setting of artificial face are all conducive to the reduction of rock fragmentation and ground vibration during blasting.