Construction Study On Controlled Blasting Scheme Of Existing Bridge Section In Songkan Tunnel

The development of transportation is the precondition of poverty alleviation.In the process of increasing the scale of highway construction,it will inevitably encounter the situation that the distance between new tunnel and existing bridge is very close.Controlled blasting technology has become an important link in tunnel excavation,but also an important factor affecting the safety and stability of adjacent structures.To ensure the safe construction of the tunnel,the safety and stability of adjacent bridge structures and the safe operation of the bridge,it is necessary to design and study the blasting parameters of the special excavation section of the new tunnel.Based on the engineering background of Songkan tunnel entrance blasting project,combined with its specific engineering practice,through the relevant data and information,the ANSYS/LS-DYNA dynamic analysis software is used to analyze.The blasting excavation process of the new tunnel is simulated,and the blasting parameters are designed and optimized.The effect of reducing the vibration of the bridge in the lower section during the blasting excavation of the new tunnel is studied.At the same time,the site blasting situation is monitored,and the optimal design of controlled blasting for new tunnel is studied.The specific research results are as follows:(1)According to the theory of numerical analysis and calculation,and using ANSYS software to establish an analysis and calculation model to optimize the blasting vibration of adjacent bridges,the double-side wall excavation blasting hole layout form and the maximum explosive charge are designed.The excavation blasting with the calculated optimal explosive charge can meet the requirements of construction design documents.(2)The blasting layout of single row shock absorber hole by step method is optimized and the blasting vibration velocity at each measuring point of Hanjiadian I Bridge under different charge quantity is calculated.The numerical model verifies that the designed blasting parameters meet the safety requirements specified in the code and design documents.(3)The monitoring scheme of blasting vibration at the entrance of Songkan Tunnel of Lanhai High Speed is designed and implemented according to the scheme.By analyzing the frequency spectrum of blasting seismic wave,the results show that the natural frequency of the bridge is less than the main frequency of the blasting seismic wave,and resonance is not the main reason for the damage of the bridge structure.By sorting out the monitoring data on site,the empirical formula of vibration attenuation applicable to geological conditions in this area is obtained,and the attenuation law of blasting vibration is obtained.At the same time,it has certain guiding significance for similar projects.