Research On Dynamic Response Characteristics And Rock-soil Damage Evolution Of Deposit Slope With Weak Interlayer Based On Shaking Table Test

Deposits slope with weak interlayer is a common natural disaster phenomenon,which has had a serious impact on the railway construction in the mountainous areas of southwest my country.In this paper,by means of data collection,theoretical derivation and shaking table test,the ground motion response characteristics and damage evolution law of a typical potential landslide point on the Dewu-Litang fault zone are studied.The main research contents are as follows:(1)Based on the results of geological survey,it is found that the soil of a typical potential landslide point on the Dewu-Litang fault zone is cohesive soil,and the underlying bedrock is quartz sandstone and slate.On this basis,combined with domestic and foreign scholars’ references and test data,the dynamic triaxial test parameters of cohesive soil and quartz sandstone are collected.At the same time,relying on the Davidenkov dynamic shear modulus ratio empirical model and Hardin damping ratio empirical model,the corresponding dynamic constitutive relationship backbone curves and envelope curves of the two rock and soil materials are proposed,and the reference shear strain is analyzed regularly.,The results show that,for the dynamic shear modulus ratio,the reference shear strain values of cohesive soil and rock decrease from top to bottom.For the damping ratio,the values of the reference shear strain of the two increase sequentially from top to bottom.(2)Based on the similarity theory,a shaking table test of a deposit slope with weak interlayer with a geometric similarity ratio of 1:10 was designed,and analyze the ground motion of the slope under the action of input seismic waves of different types and different seismic intensities Respond to laws and damage phenomena.The test results show that the failure phenomenon of the deposit slope with weak interlayer is the classic " crack-slip-shear three-stage" failure,namely stage 1: the top of the sliding body squeezes the middle part and develops downward,causing the top to crack.Stage 2: The top of the sliding body and the middle part of the movement are basically the same.Stage 3: The displacement of the bottom of the sliding body is greater than that of the top of the sliding body,and the two stretch each other.The middle part of the sliding body develops faster to the locked section,which causes the cracks to develop gradually.Eventually,the whole accumulation is destroyed.Generally speaking,the landslide is a balanced and gradual process.At the beginning of the earthquake,under the influence of gravity and seismic force,the soil on the surface of slope began to peel off;as the ground motion continued,the top of the sliding body cracked,The cracks on the surface of the sliding body increase and develop at the front edge locking section;finally,the locking section is damaged,the sliding surface is penetrated,and the sliding body slides out from the cutting outlet of the leading edge to form a landslide.(3)Under the action of the Wenchuan Wolong seismic wave of different seismic intensities,the PGA shows different degrees of elevation magnification in the direction of the free surface and the vertical direction of the deposit slope.And the elevation magnification effect in the free surface direction of the slope is obviously stronger than that in the vertical direction;The acceleration response spectrum and the Hilbert spectrum also increase with the increase in elevation,and the corresponding peak value increases,and under the action of the same kind of seismic wave,the amplitude of the acceleration spectrum increases with the increase of the peak acceleration of the input seismic wave.The inconsistency of the movement between the sliding bed and the sliding body leads to the occurrence of landslides.Before the accumulation body is destroyed,the acceleration peak value and the Fourier amplitude of the empty surface of the accumulation body are greater than the sliding bed,and the excellent frequency bands of the two are basically the same;When the body begins to fail,the acceleration peak value and the Fourier amplitude of the adjacent surface of the accumulation body are smaller than that of the sliding bed,and the superior frequency band gradually shifts to low frequency,while the main frequency and amplitude of the Fourier spectrum of acceleration in the sliding bed are basically unchanged.(4)Based on the transfer function theory,study the modal parameters of the deposit slope with weak interlayer under earthquake action.The results show that before the slope collapses(input ground motion peak acceleration is 0.4g,0.5g),the frequency response law of different measurement points in the accumulation body and bedrock is basically the same;With the continuous increase of the input seismic energy,after the slope collapses(the peak acceleration of the input seismic wave is 0.6g),the internal measurement points of the bedrock show that its natural frequency is slightly reduced,the damping ratio is slightly increased,and the inside of the accumulation body The measurement points show that the natural frequency is suddenly reduced,the damping ratio is increased,and the top of the accumulation body is damaged first than the bottom,which is consistent with the experimental damage.At the same time,as the input intensity of ground motion increases,before the slope collapses,the measured points in the accumulation body show that the dynamic shear modulus ratio is significantly reduced,and the top is significantly reduced compared to the bottom,while the measured points in the bedrock show The dynamic shear modulus ratio is basically unchanged,which is basically consistent with the experimental phenomenon and the changing law of natural frequency.