Impact Of Environmental Vibration Induced By High-speed Railway On Precision Machine And Research On Its Vibration Isolation Technology

The mileage of high-speed railway in China is 2.5 thousand kilometers by the end of2017,ranking first in the world.China’s high-speed railway developing rapidly,causing increasingly prominent environmental vibration.Excessive vibration will cause adverse effects on the train operation safety,comfort,safety and indoor environment surrounding buildings,residents of the normal work and life and the precision instrument and equipment.At the same time,the progress of science and technology promotes the development of ultra precision machining,and environmental vibration has become an important factor affecting the ultra precision machining.Therefore,the analysis of the environmental vibration produced by high-speed railway and the research of vibration isolation for precision equipment are of great significance for the healthy and sustainable development of high-speed railway and precision machining industry.Based on the theory of vibration test and the signal analysis,vibration test under the excitation of high-speed railway are taken out in the workshop planning to install precision boring machine.The dynamic performance of the site and its vibration response under the excitation of high-speed railway are studied by time and frequency analysis of test data.And then,combined with the existing domestic and foreign environmental vibration evaluation standards,the impact of environmental vibration on precision instruments and equipment is evaluated,and vibration sensitivity analysis of precision boring machine is carried out according to the technical data of boring machine.Finally,based on the theory of vibration isolation,a vibration reduction scheme for precision boring machine equipment foundation is put forward.The effect of vibration isolation for boring foundation is analyzed and evaluated by theoretical calculation,numerical analysis and in situ testing.Conclusions are as follows:(1)Ground vibration of the sites in workshop last 10~15 s as the train passing by,main vibration sustains 5~6 s.The vibration amplitude is increased by 5~30 times,and magnification degree of the amplitude is influenced by the factors of train load,speed and site condition.Vibration amplitude in direction of cross bridge is the largest,and the vibration amplitude in direction of longitudinal bridge is about the same as the vertical.The frequency of the ground vibration is at the range of 4~40 Hz,which belongs to the low-and-mediumfrequency vibration.(2)Due to the influence of the foundation layout of the workshop,vibration in the direction of cross bridge is enlarged by superposition.Vibration near 10 Hz is too large to exceed the limit vibration value of the equipment in workshop.The vibration in the direction of longitudinal bridge and the vertical is smaller,which can satisfy the vibration limit of buildings with low vibration sensitivity in residential areas.(3)The response frequency of the site in workshop is close to the natural frequency of the machine under the train load,and the vibration acceleration in direction of cross bridge is beyond the limit of the boring machine that is to be installed.Vibration at the characteristic frequency in direction of the cross bridge ought to be focused in the design of the foundation isolation.(4)On the basis of vibration measurement,site investigation,vibration limit value and dynamic characteristic analysis of the boring machine,three levels of isolation and fortification are put forward as follow: The vibration isolating filled ditch and gravel concrete cushion is used as the first vibration isolation;and the isolation barrier between the line and the workshop is considered to be the second vibration isolation;and the vibration isolator set between the equipment and the foundation is the third vibration isolation.The first level vibration isolation is studied from three aspects of design,construction and effect evaluation.(5)The dynamic time history analysis of the established boring machine foundation vibration isolation numerical model under the high-speed rail excitation is realized by ANSYS software,which can avoid complex dynamic calculation of vehicle-bridge coupling,and the results of numerical calculation are in good agreement with the measured results.The results show that vibration isolation filled ditch and dinas concrete cushion can effectively reduce the vibration amplitude near the predominant period of the boring machine foundation.After the isolation treatment,the vibration indexes on the foundation platform have met the installation requirements of the equipment.The above research results can provide reference for sensitive equipment along the highspeed rail.