Drilling and blasting technology for closely crossing existing shield tunnel

Taking Yitian Road Tunnel of Guangzhou-Shenzhen-Hong Kong Passenger Dedicated Line as the engineering background，the vibration response of the existing shield tunnel lining structure under blasting is studied. Based on the stress wave theory，the allowable velocity of the blasting vibration of shield tunnel lining segments is calculated and verified by the field data. Combining with the field monitoring data of existing tunnels，the variation law of vibration velocity of lining segments is analyzed，and vibration reduction measures and optimized blasting scheme are put forward to ensure the operation safety of the existing shield tunnel. The results show that the maximum vibration velocity of the existing tunnel lining segment reaches 7.19 cm/s in the process of blasting construction，which is less than the calculated safety allowable vibration velocity of 9 cm/s. The segment joints are not damaged，and the calculated safety allowable vibration velocity of the lining segment can be regarded as a reference for similar projects. When drilling and blasting method is used to closely underpass the existing shield tunnel，the blasting vibration velocity of existing tunnel lining segments can be effectively reduced by using electronic detonator initiation technology combined with appropriate vibration reduction measures to ensure the safety and stability of the structure.