Study On Safety Of Subway Tunnel Blasting Construction To Adjacent Transmission Towers

At present,in the process of tunnel excavation,drilling and blasting method is still favored by domestic and foreign construction teams for its advantages of high efficiency and economy.Due to the limitation of topography and landform,the construction lines of rail transit are close to and even pass through the existing transmission towers,especially in the case of close proximity.Blasting construction will inevitably cause the vibration response of transmission tower,and transmission tower is a high-rise structure which is sensitive to vibration load and inclined deformation.Therefore,it is of great practical and theoretical significance to study the influence of blasting vibration of subway tunnel on nearby tower.In this paper,the influence of tunnel blasting construction on nearby transmission tower is studied with the combination of field measured vibration data and numerical simulation based on the section project of Xiazi Bian Station to Jinshan Station of Chongqing Rail Transit Line 4.The main research work of this paper is as follows:① The theory of blasting stress wave and the failure mechanism of rock blasting are analyzed,the formation,classification and propagation characteristics of seismic wave are introduced,and the main factors affecting the propagation of blasting seismic wave are summarized.②The blasting monitoring scheme of Xiazi-Jinshan Station of Chongqing Metro Line 4 is briefly described,and the actual monitoring data of the vibration velocity of transmission tower during tunnel blasting construction are fitted by least square method.The dynamic response law of the base particle of the transmission tower is obtained.Combined with the related blasting vibration control standard,the monitoring data has high reliability.③According to the actual blasting construction conditions of subway tunnel engineering,a three-dimensional model was established by using MIDAS/GTS software,and the peak vibration velocity of the near transmission tower foundation during tunnel blasting was calculated.The vibration parameters of Sadowski’s formula in horizontal direction of tower’s vibration velocity are obtained by fitting and analyzing the data.Then several different methods are used to optimize the surrounding rock parameters and finally the vibration parameters of the Sadovsky formula which are more consistent with the experimental results in the field are obtained.The results show that dynamic surrounding rock parameters should be used in blasting vibration calculation,and static surrounding rock parameters can conservatively estimate the disasters caused by vibration effects.④Using the optimized model,the influence of different sizes of the trench on the damping effect is analyzed.The results show that in the blasting construction of subway tunnel,the blasting seismic effect can be weakened by setting the shock absorption ditch in the middle of the nearby transmission tower,and the vibration absorption effect can be better by increasing the length and depth of the damping ditch properly.The width and width of the trench have little effect on the damping effect.⑤According to the calculation formula of vibration velocity attenuation law of transmission tower base obtained by numerical analysis,the maximum charge quantity under subway tunnel station near the transmission tower can be calculated,which can be used as a reference for field construction.