Study On Vibration Effect Of Blasting Construction Of New High-speed Railway Tunnel On Existing High-speed Railway Tunnel

With the continuous increase of traffic tunnels in China,there are more and more cases of small clear distance tunnels and new tunnels near existing tunnels,and the influence of new tunnel construction on existing tunnels has become a problem that cannot be ignored.Mine excavation is the main excavation method of mountain tunnel.When two tunnels are close to each other,the blasting construction of new tunnel has adverse effects on the stability of surrounding rock and lining structure of the existing tunnel.Therefore,it has become the focus of attention to determine the blasting construction method of new tunnel to ensure the safety and normal operation of the existing tunnel.The new Pinggongshan tunnel of Shantou high-speed railway spans the existing Pingfengshan tunnel,the net distance between the two tunnels is 16.5m,and the tunnel intersection Angle is 15°8 ’.ANSYS/LS-DYNA software simulation research and measured data are used to analyze the impact of the blasting construction of the new Pinggongshan tunnel on the adjacent existing Pingfengshan tunnel below.The research contents and achievements of this thesis are as follows:(1)By studying the influence of new tunnel blasting on existing tunnels under different surrounding rock grades,excavation methods and tunnel angles,the following conclusions are drawn: With the increase of surrounding rock grades,the particle vibration velocity of existing tunnels increases,the vibration wave energy increases,the main vibration frequency decreases gradually,and the maximum tensile stress increases;The two-step and three-step excavation has the least influence on the vibration velocity and stress of the existing tunnel,which is better than the excavation of the full section,the second step and the third step.The vibration velocity of the existing tunnel lining decreases with the increase of the included Angle of the two tunnels in the controlled blasting construction.The vibration velocity of different included Angle is 90°,0°,30° and 60° from large to small in the electronic detonator blasting construction.The maximum tensile stress appears at the left and right arches,and the maximum tensile stress decreases with the increase of the cross angle.(2)By analyzing the influence of different types of hole delay interval,the delay interval between different holes and different construction methods under different circular footage,the following conclusions are drawn: When the delay interval of different types of hole is more than 5ms,the vibration velocity and maximum tensile stress of the existing tunnel reach the minimum and tend to be stable,and the delay interval of different types of hole should be more than 5ms;When the delay interval between holes is 2ms,the vibration waves generated by different holes cancel each other,and the particle vibration velocity of the existing tunnel is the minimum.The influence of controlled blasting construction on the existing tunnel with 1m,2m and3 m cycle footage is analyzed.The influence zones of controlled blasting construction on the existing tunnel with different cycle footage are given,and the construction interval of electronic detonator blasting and the optimal cycle footage are determined.(3)Analyze the vibration velocity law of the existing tunnel measured in the field,compare the vibration velocity law of the measured data and the numerical simulation data,verify the correctness of the numerical simulation,use the least square regression analysis of Sadowski formula to determine the vibration velocity attenuation law parameters,the nearest point distance of the two tunnels and the amount of explosives into the fitting formula to determine the nearest point vibration velocity value below the allowable value.The delay interval between holes can be adjusted to further reduce the vibration velocity of the existing tunnel.