Experimental Study On Vibration Damping Rule Of Free Space Under Environmental Excitation

High-tech electronics factories and precision instruments in large scientific experimental devices have high control requirements for environmental vibration.For example,the micro-vibration control standard of the IC building reaches VC-D?1/3 octave speed is 6?m/s?.However,equipment inside the building is inevitably adversely affected by environmental vibrations caused by traffic loads around the building and power equipment such as pump and air-conditioning rooms.In order to reduce the influence of environmental vibration on precision instruments and equipment,it is necessary to study the characteristics of vibration source and the propagation of vibration in soil.This paper takes the proposed Synchrotron Radiation Facility project as the background.The on-site measured method is used to study the vibration response characteristics and attenuation law of the site under traffic load and vertical harmonic load.Specific research content includes:?1?The hazards of environmental vibration,the relevant standards of vibration control,and the research status of vibration propagation rules at home and abroad are reviewed.Theoretical summary of the three-dimensional wave equation of infinite uniform elastic body.The existing formulas for predicting vibration attenuation are introduced in detail.The differences and relations between Bornitz formula,Yang Xianjian formula and Wang Yisun formula are analyzed.?2?The field vibration response was tested by using a dregs heavy-duty vehicle on the proposed site to simulate the traffic load vibration source on the compacted soil road.The attenuation rule of ground vibration under different vehicle speeds and loads is analyzed in time domain and frequency domain.It is found that when the same dreg truck travels on compacted soil road,increasing the speed will increase the vibration response of the site,while increasing the weight of the truck may reduce the vibration response of the ground.Taking Yang Xianjian's vibration attenuation prediction formula proposed in the Code for Design of Dynamic Foundation GBJ40-79 as a model,the field measured data is fitted,and the fitting results are in good agreement with the measured values.?3?The field vibration response test of exciter under harmonic vertical load was carried out on the proposed site.The test frequency is 10⁵0Hz.The response characteristics of vertical vibration velocity of site under single frequency vertical vibration and the attenuation rule of vertical vibration velocity of site with different excitation frequencies are analyzed.Based on Yang Xianjian's vibration attenuation prediction formula and the measured results of vertical vibration velocity response under vertical harmonic load,the vibration damping curve is fitted.The fitting results show that the energy absorption coefficient of soil is related to the excitation frequency.The larger the excitation frequency is,the larger the value?₀ is.