Study On The Vibration Influence Of Subway On Power Tunnel And The Effect Of Vibration Reduction And Isolatio

With the development of urbanization and underground space,there are inevitably overlapping areas between power tunnels and subway tunnels,and the vibration of power tunnels caused by subway operation will induce structural damage and leakage of power tunnels.Therefore,this paper aims to explore the vibration influence of power tunnel under subway load and the measures to reduce vibration isolation.Guangzhou 500 k V Suixi Chuting power transmission project is selected as the original model.Based on the similarity theory,the 1 : 15 scale model test is used as the research method to study the vibration response mechanism of power tunnel under the influence of different axis intersection angles,different spatial parallel angles,different distances,different speeds,different loads and frequencies under subway vibration.Through the research methods of scale model test and numerical simulation,the important conclusions are as follows :(1)A loading system which can truly reflect the running state of subway train is designed and developed.It includes an adjustable counterforce frame system and a movable and variable speed power trolley system.The adjustable counterforce frame system can cope with the uneven deformation of the surrounding rock soil during the loading process,and the subway tunnel will be separated from the tunnel structure due to the settlement of the subway tunnel.The movable and variable speed power car system restores the stop,start,uniform speed and acceleration of the subway train when the subway is running.(2)The dynamic response law of subway tunnel-soil-electric tunnel system under subway load is obtained by scale model test.The results show that the vibration propagation law along the subway or electric tunnel structure is the fastest attenuation parallel to the track direction,followed by the horizontal perpendicular to the track direction,and the vertical attenuation is the slowest.The maximum acceleration area in the soil is located at the lower part of the subway tunnel,followed by the side and the upper part.The attenuation in all directions gradually slows down.When the vibration propagates in the soil,the lateral attenuation is the fastest,the longitudinal attenuation is the second,and the vertical attenuation is slow.Through spectrum analysis,it is found that soil has an inhibitory effect on high frequency.When the vibration wave encounters underground structures such as power tunnels,the refraction and reflection of the wave will occur,which will cause the wave to overlap and amplify the vibration locally.(3)Through different load and frequency,different speed and other loading methods,it is found that the vibration waveform of the tunnel structure and the soil is consistent with the load waveform of the vibration source.The acceleration in the tunnel and soil does not have a sine waveform at low frequency,and it is a sine waveform at high frequency.The sweep load increases linearly and then decreases linearly in the sweep period.When the train speed increases,the acceleration and high frequency amplitude of soil and tunnel structure increase.The acceleration increases with the increase of train speed.On the one hand,it is due to the increase of the effective amplitude of acceleration at high frequency.On the other hand,it is due to the increase of additional load caused by track irregularity at high speed.When the speed increases,the lower soil pressure of the tunnel structure increases and the upper soil pressure decreases.When the vehicle speed increases,the dynamic strain decreases and the decreasing trend is small.(4)Through the test of the position relationship of different axis crossing angles,different parallel space angles and different distances,it is found that the axis crossing angle has an effect on the vibration response of the power tunnel.The acceleration gradually decreases from 0 ～90 degrees and the decreasing trend is from 0 ～ 45 degrees to 45 ～ 60 degrees.The degree is slow,and the 60 ～ 90 degree is relatively gentle;different parallel space angles have a certain degree of influence on the vibration response of power tunnels.When the power tunnel moves clockwise along the bottom of the subway tunnel to the top,on the one hand,the vibration peak area is transferred from the bottom of the power tunnel to the top counterclockwise,that is,from the bottom when it is at the top to the bottom of the left when it is in the upper right corner,the left when it is in the right part,and the upper left when it is in the lower right corner to the top when it is at the bottom.On the other hand,the vibration peak shows a trend of decreasing first and then increasing.When the power tunnel is located at the bottom of the subway tunnel,the peak acceleration is the largest,followed by the top,and the left is the smallest.Under different distance conditions,the acceleration gradually decreases as the distance increases.(5)EPS polyethylene foam consumes vibration energy through the compression deformation of internal foam bubbles;rubber particles can absorb vibration energy through their own deformation and friction between particles.Both of them have good vibration isolation effect.In contrast,EPS has better vibration isolation effect.