Mutual Influence Analysis And Optimization Research On Blasting Construction Of Shallow Buried Small Clear Distance Highway Tunnel

In today's booming urban traffic engineering,due to the limitations of the site environment or line selection conditions,the clearance of adjacent tunnels during construction cannot meet the requirements of the specification.Therefore,small clearance tunnels have emerged.Drilling and blasting method is often used in tunnel excavation.The energy wave generated by blasting must have certain influence on the stability of adjacent caverns.Therefore,studying the influence of blasting vibration on initial support and surrounding rock has become an urgent solution in the construction process problem.This paper combines the Mingyueshan tunnel project in Jiangbei District of Chongqing City,through the investigation of the actual project site,using the theory of rock blasting and numerical simulation to carry out systematic research,and then combined with the field measured data collaborative analysis and comparison with the simulation results,comprehensive After analysis,the following main conclusions are drawn:(1)Numerical simulation and on-site blasting vibration monitoring results show that when the first tunnel blasting is excavated,the initial vibration of the adjacent cavern is higher than that of the backside,and the maximum vibration velocity appears at the side of the blasting side.The maximum vibration velocity is attenuated along the circumferential and longitudinal directions of the tunnel.The blasting vibration velocity decreases with the increase of the blasting distance.When the longitudinal spacing of the face is more than 30 meters,the blasting construction has less influence on the adjacent cavity.(2)When the safety vibration velocity method is used to evaluate the concrete failure standard,the section at the face of the face is taken as the research object,and the maximum vibration velocity appears at the tunnel vault.The damage distance is9.11 m.When the concrete ultimate tensile stress method is the failure standard,the maximum pull The stress appears at the right side of the arch,and the damage distance is 8.21 m.Considering the redundancy for safe production,the dome vibration velocity is used as the basis for judging the initial damage of the blasting vibration.At the same time,the relationship between the spray mixing and the damage range at different ages is obtained,and the reinforcement measures are taken in advance to guide the construction.(3)The influence of blasting construction on the initial branch of the first tunnel under different conditions and different working conditions.Under different working conditions,the variation of the vibration velocity of each key particle on the cross section of the adjacent branch is similar,three-way vibration velocity The medium-horizontal radial direction vibration speed plays a leading role,and the vibration monitoring of the vibration velocity in this direction should be strengthened and should not exceed the allowable safety vibration speed.(4)The measured value and the simulated value were compared and analyzed.The analysis results show that the measured values are close to the calculated values,and the difference between the two vibration speeds is less than 1cm/s,which indicates that the numerical simulation is more reliable.