Test On Influence Of An Annular Trench On The Vibratiion Isolation

In recent years,with the further development of urbanization construction in our country,the artificial vibration caused by construction,mechanical operation,transportation facilities and so on has adversely affected the work and life of nearby residents and the normal use of precision instruments and equipment,and even endangered the safe use and maintenance of nearby buildings and ancient buildings when serious.At present,the installation of vibration isolation barrier is one of the methods to solve this environmental vibration.The vibration isolation barrier can be divided into two types according to the type of structure,continuous vibration isolation barrier and discontinuous vibration isolation barrier.The annular trench is a kind of continuous vibration isolation barrier.In this paper,the vibration isolation effect and its vibration isolation area of annular trench are studied by means of outdoor test.Under the conditions of this test,the conclusion beneficial to engineering practice is obtained,which enriches the relevant vibration isolation theory and provides a reference for the rational design of annular trench.First,the effect of vibration isolation:In order to study the vibration isolation effect of the annular trench,the depth,width,vibration source distance and arc length of the annular trench are analyzed by using the surface amplitude reduction ratio as the evaluation index of the vibration isolation effect.The results show that the depth of the annular trench,the distance from the trench to vibration source and the length of the arc are the important factors affecting the vibration isolation effect,and the width of the trench has little effect on the isolation effect.When the ratio of trench depth to the Rayleigh wave length is 0.74 ~ 0.86,the vibration isolation effect of the annular trench is remarkable;and when the ratio is greater than 0.86,increasing the depth of the trench is not beneficial to strengthen the isolation effect.When the ratio of vibration source distance to Rayleigh wave length is 1.45 ~ 1.69,the trench can achieve good vibration isolation effect,when the ratio is less than 1.45,the isolation effect can be significantly enhanced by increasing the source distance,and when the ratio is greater than 1.69,the increase of vibration isolation effect is not significant.In addition,the arc length of the annular trench is also an important factor affecting the isolation effect of the trench.When the ratio of the arc length to the Rayleigh wave length is 3.59~4.48,good isolation effect can be obtained,but the further increase of the ratio will not significantly enhance the isolation effect.Second,the effective isolation areas:The contour map of the amplitude reduction ratio was drawn,the area with the amplitude reduction ratio of not more than 0.35 is used as the evaluation index of the effective vibration isolation area,and the influence of the geometric parameters such as depth,width and distance of the annular trench on the effective vibration isolation area is analyzed.The results show that the depth of the trench,width of the trench,the distance from trench to the vibration source and center angle of the trench have different effects on the effective vibration isolation area.When the ratio of trench depth to Rayleigh wave length is 0.54~0.77,the ratio of trench width to Rayleigh wave length is 0.23~0.33,and the ratio of the distance from trench to the vibration source to Rayleigh wave length is 1.18~1.52,the good effective vibration isolation area of annular trench can be obtained,and under the conditions of this test increasing the ratio of each parameter is not beneficial to enlarge the effective vibration isolation area.The central angle of annular trench is an important factor affecting the effective vibration isolation area,increasing the angle can obviously enlarge the area of the effective vibration isolation area.When the angle is 90,a discontinuous effective isolation area will be formed in the isolation area.The selection of the angle is related to the frequency,when the effective isolation area of the same size is achieved,and the angle increases with the decrease of the frequency.