Research On The Vibration Effects Of High Speed Railway Tunnel Blasting On Adjacent Ultrahigh Voltage Iron Towers

Due to the limitations of terrain conditions,more and more high-speed railways need to pass through mountains,and tunnel engineering in complex mountainous environments is gradually increasing.When there is a high-voltage iron tower near the tunnel blasting construction,it is easy to cause harm to the tower foundation and affect the operation of the transmission line.At present,domestic and foreign scholars’ research on the impact of tunnel blasting on adjacent building structures is more focused on low-rise buildings,and there is relatively little research on sensitive high-rise buildings such as high-voltage iron towers.The research on the impact of tunnel blasting on adjacent high-voltage iron towers mainly focuses on the static aspect,and there are still many problems that need to be solved urgently in the study of blasting dynamic response.This article took the Langjiafan Tunnel project of the Hangzhou Wenzhou Railway as the background,and used a combination of on-site monitoring and numerical simulation methods to study the vibration impact of tunnel blasting on three adjacent ultra-high voltage iron towers.The vibration response law of the tower foundation and body under tunnel blasting was analyzed,and the vibration influencing factors of the high voltage iron tower under tunnel blasting were discussed in detail.The main research content was as follows:(1)By conducting on-site monitoring of the foundation of the iron tower,the impact of tunnel blasting on the vibration of adjacent ultra-high voltage iron towers was studied.The results showed that the vibration velocities in the horizontal radial,horizontal tangential,and vertical directions of the iron tower foundation continuously increased with the decrease of the explosion center distance,and the vibration velocities in the vertical direction were significantly higher than those in the horizontal direction;When the distance between the explosion centers wes 30 meters,the vibration velocity would increase exponentially,and the closer the explosion source was to the tower foundation,the greater the variation in vibration velocity.The vibration waveform of the tower foundation was divided into multiple segments,and the peak vibration velocity of each segment showed a decreasing trend,indicating that on-site blasting could use a multi-stage delayed detonation network to reduce tower foundation vibration.The main vibration frequency distribution of the three iron towers was relatively scattered.After fitting,it was found that the main frequency continuously decreased with the increase of blast center distance,and the main frequency was mainly distributed between 10 Hz and50 Hz,while the natural frequency of the building was between 1 Hz and 10 Hz.Therefore,blasting wiould not cause resonance of the iron towers.(2)Based on the on-site monitoring results and the Sadovsky formula,the vibration velocity results of the on-site monitoring were fitted to obtain the vibration propagation attenuation formulas of the three iron towers under the conditions of this project,and the maximum allowable explosive amount for a single section on site was analyzed and predicted.(3)A three-dimensional numerical model was established using Midas/GTS NX to simulate the impact of tunnel blasting on the vibration of adjacent ultra-high voltage iron towers.The results showed that the peak vibration velocities of the three tower foundations in the horizontal radial,horizontal tangential,and vertical directions all increased with the decrease of the distance between the explosion centers.Among them,the vibration velocity in the vertical direction was most affected by the distance between the explosion centers,indicating that the vibration in the vertical direction of the tower foundation on site should be the main monitoring object.The vibration velocity results of numerical simulation were greater than those of on-site measurement,but the trends of the two were consistent,with a maximum relative error of less than 20%.Therefore,the three-dimensional numerical model was reliable and had high simulation accuracy.(4)Analyzed the displacement of the tower foundation and the dynamic response of the tower body at different heights through numerical simulation research.The results showed that the vertical displacement changes of the four tower foundations of the iron tower were basically consistent.The displacement quickly reached its maximum value during the period of t=0.05 s～0.1 s,and after a short period of fluctuation,it immediately decreased to a certain value and tends to stabilize.The horizontal radial,horizontal tangential,and vertical vibration velocities of particles at different heights of the tower body decreased with the increase of tower height.The members of the three iron towers were all subjected to tension at the upper part and compression at the lower part,and the maximum axial tensile stress was distributed at the top of the iron tower.(5)A numerical model was established using Midas/GTS NX to analyze the factors affecting the vibration of high-voltage iron towers under tunnel blasting.The results showed that the vibration velocity of the tower foundation increased with the increase of the surrounding rock grade,and the vibration velocity in soft rock was greater than that in hard rock;When there were soft rock interlayers in the rock,it also affected the vibration velocity.The thicker the interlayers,the greater the vibration velocity of the tower foundation;The farther the interlayer was from the ground,the greater the vibration speed of the tower foundation;The larger the cross-sectional size of the tunnel,the greater the vibration velocity of the tower foundation,and the impact range of blasting wiould also increase with the increase of cross-sectional size.