Shaking Table Test Study On The Seismic Pergormance Of Mountain Tunnel With Large Section

With the rapid development of the national economy,the development of the mountain tunnel with large section engineering in Fujian is especially rapid.Especially,in order to meet the need of mountain tunnel with large section that increases the span for the more lanes,which structure is complex and the seismic performance is weak.And Fujian is located in the Circum-Pacific seismic belt.Therefore,the hidden danger of the mountain tunnel with large section instable failure caused by earthquake can not be ignored.In this paper,the model test is used to study the dynamic response and dynamic characteristics of the mountain tunnel with large section during the earthquake,and also to explore the deformation and failure characteristics of the tunnel model.The main conclusions of this paper are as follows:(1)According to the geological conditions and the experimental research objectives,the simplified tunnel prototype size is determined,which makes the length,width and height to be 930dm*240dm*390dm;According to the similarity theory,the similarity ratio of the geometric size,acceleration and elastic modulus is determined respectively as 1/40,1/1 and 1/30.And the dynamic similarity relation of other physical quantities is deduced.Finally,the length,width and height of the tunnel model is determined to be 310cm*80cm*130cm.And the thickness,section height and width of the lining structure is determined as 2.5cm*43cm*63cm.(2)The amplification coefficient of acceleration amplitude of each point in the tunnel model is more than 1,which indicates that the seismic wave in the tunnel model is obviously enlarged;And the amplification coefficient of each measurement point is decreased with the increase of the amplitude of the input acceleration,and finally tends to be stable;Under the same acceleration amplitude,the vertical amplification factor of the measuring point increases with the height increasing,and the top of the tunnel model is the biggest;The response of different seismic wave to the acceleration of the measuring point is strong.In the smaller earthquake magnitude,the seismic wave of the energy disppersion is more obvious to the acceleration response of the structure system than the bigger earthquake magnitude.With the increase of the earthquake magnitude,the seismic wave of the energy concentration is strong to the acceleration response of the structure system;The dynamic soil pressure and dynamic stress of the lining increases with the input of vibration acceleration amplitude increased;Especially,the dynamic soil pressure near the arch waist of the lining is more obvious with the increase of the amplitude of seismic wave as the dynamic stress near the skewback of the lining;(3)Through white noise excitation,the fundamental frequency of the tunnel system is analyzed,and the fundamental frequency of the soil in the model tunnel system is located near the 9.8Hz,and the fundamental frequency of the lining structure is located near the 26.5Hz.Compared with the initial state,the damping ratio of the lining invert,arch waist,vault and the surface of soil is increased by 9.2%,12.5%,9.6%and 12.6%after the 0.4g earthquake wave action;In the frequency spectrum,it is indicated that the predominant frequency of soil is mainly in the vicinity of 25Hz.Below the frequency of 20Hz and above 30Hz,the frequency components were significantly decreased,which indicated the filtering effect of the soil and soil;With the increase of height,the effect of filtering is more obvious;And with the increase of the amplitude of the earthquake,the predominant frequency of the soil is decreasing;The spectral characteristics of the tunnel structure system is independent of the characteristic frequency of the input seismic wave,which is only related to its own property.(4)When the tunnel model is loaded into 0.6g seismic wave,the lining is damaged,the main cracks are distributed in the arch waist,skewback and invert.The cracks are mainly developed as longitudinal cracks,and a small amount of oblique cracks,which angle is about 45 degrees.