Experimental Studay On Vibration Isolation Performance Of Single-row Vibration Isolation Piles In Rail Transit

With the increase of rail transit operating speed,operating mileage and vehicle axle load,along the residential areas,ancient buildings,institutions of higher learning with high-precision instruments and factories,such as the vibration damage caused by more prominent.In this paper,the field test method is used to study the vibration isolation of Rail Transit on land and viaduct by using single-row piles and annular piles.It is proposed to establish a quantitative relationship between the geometrical parameters of piles and Rayleigh wavelength,then the variation of vibration isolation effect of single-row vibration isolation piles is analyzed,and the regional vibration characteristics of single-row vibration isolation piles under different excitation frequencies is analyzed.The relevant studies mainly cover the following areas:(1)In one-dimensional view,the vibration of the control point behind the pile is analyzed,and the geometric sizes of the single-row piles arranged in a linear and circular arrangement are compared with the Rayleigh wavelength.Further analysis of the effect of the correlation between the different geometric sizes of single-row vibration isolation piles and the Rayleigh wavelength on the vibration isolation effect of single-row vibration isolation piles.(2)Based on the research results from one-dimensional perspective,the vibration characteristics of single-row vibration isolation piles with linear and annular arrangement under the action of the representative exciting frequencies(low frequency,middle frequency and high frequency)in two-dimensional perspective are studied.At the same time,the variation of effective vibration isolation area in the region behind piles is compared under different excitation frequencies.(3)The vibration isolation mechanism of linear and annular single-row vibration isolation piles as a vibration isolation barrier is analyzed from two-dimensional perspective.Then,the vibration characteristics distribution of single-row vibration isolation piles in two-dimensional view is obtained.In the above field tests of single-row piles and annular piles,the main conclusions are as follows:(1)For single-row piles,when the ratio of pile length to wave length is after 0.638,the pile length continues to increase,the vibration isolation effect of piles does not increase significantly,and the rate of Ar(Amplitude reduction ratio)value decrease tends to be stable;When the ratio of pile spacing to wavelength is between 0.013 ~ 0.084,the variation of Ar value is slow and low,single-row piles can get better vibration isolation effect,that is,when the width of pile section increases,the effect of vibration isolation changes little;When the ratio of section width to wavelength is after 0.058,with the increase of pile section width,Ar changes slowly,vibration isolation effect of single-row piles does not improve significantly;When the ratio of vibration source distance to wavelength is between 0.291 ~ 0.357,the Ar curve has a regional minimum point,and the isolation effect of single-row piles is relatively good,At the same time,it is shown that the best position of vibration isolation pile is not the closer to the vibration source.(2)In the regional analysis of single-row vibration isolation piles with linear arrangement,when the excitation frequency increases from low frequency to high frequency,the effective isolation area decreases and the isolation effect weakens gradually.In the propagation process of Rayleigh wave produced by low and medium frequency vibration,the vibration isolation effect of low and medium frequency vibration by linear single row vibration isolation piles is better.(3)For single-row vibration isolation pile with circular arrangement,when the ratio of pile length to wavelength reaches 0.647,The slope of Ar curve is close to 0,and further increase of pile length has little effect on the vibration isolation effect.When the ratio of pile spacing to wavelength reaches 0.100 ~ 0.138,with the increase of pile spacing,the variation of Ar curve tends to be gentle and maintain a low level.After 0.138,with the pile spacing increases,and the Ar value curve presents an increasing trend,which shows that the effect of vibration isolation is gradually weakened.When the ratio of circumferential length to wavelength is after 2.627,The slope of Ar curve is close to 0,if the circumferential length of single-row vibration isolation piles is increased,the effect of vibration isolation is not obvious.(4)The geometric parameter combination with larger pile length,smaller pile spacing and moderate vibration source distance,and the ratio of the geometrical dimension of the pile to the wavelength of Rayleigh wave is kept within the range of the test conclusion is preferred to obtain better vibration isolation effect.When the single-row vibration isolation pile with circular arrangement is used to isolate the vibration of rail transit,further comparison of the proportion of the ?(Area ratio of effective vibration isolation area)can be seen,which in the low-frequency vibration when the priority of setting up the 360° ring-pile barrier and the medium and high excitation frequency is preferred to setting the 270° ring-pile barrier to obtain the maximum ?.Considering that 360° ring-pile barrier and 270° ring-pile barrier occupy more space in actual arrangement,so when the terrain conditions of the project are limited,the 180°ring-pile barrier should be set to obtain a stable ? for low,medium and high excitation frequency.The performance of 90° ring-pile barrier ? is the smallest,generally not recommended.