Research Of Blast Excavation Footage On Large-Span Tunnel Construction With Bench Method

This article mainly adopts the combination of field test and numerical simulation.Taking the Wanxing Road Tunnel in Jiangbei District as the engineering background,the actual construction conditions of the large span Wanxing Road Tunnel are calculated and analyzed to study the influence of the step blasting on the safety of tunnel excavation when the large span tunnel step method is constructed.The main contents are as follows:1.According to the field monitoring data of Wanxing Road Tunnel Project,the measured data of tunnel upper bench blasting monitoring under bench method are obtained.By using the regression analysis,the V-R curve of the vibration speed and the detonating distance under the blasting condition is obtained,which provides the engineering basis for the construction of large span tunnel bench blasting under similar working conditions.2.The excavation method of large span tunnel under different working conditions is simulated,and the blasting vibration law of the upper step lining in the bench blasting method for large span tunnel construction is analyzed.The results show that the larger the footage of the upper bench blasting is,the greater the blasting vibration peak is at the key point.3.Analyzing the vibration response law of the lining particle during the blasting process,considering the safety status of the tunnel structure,the safety of the tunnel construction and the economic cost and so on,the construction of the upper bench blasting in the large span Wanxing Road Tunnel is put forward.The optimum excavation footage is 2m when the surrounding rock is III and IV,and the optimum excavation footage is 1.5m when the surrounding rock is V grade.4.According to the simulated tunnel stress analysis of upper bench blasting footage 1.5m,the stability of the step lining structure of the large span tunnel under the step method is verified.