Study On Dynamic Response And Disaster Mechanism Of Loess Slope Under Vehicle Vibration

This paper’s research object is the Loess Highway slope that widely distribute in northern Shaanxi.By using the combining field investigation,Engineering geology analysis,field monitoring,laboratory tests and microscopic analysis.This paper generalized the deformation failure mode and characteristics of typical loess highway slope,obtained the dynamic response and propagation law of the loess slope under the action of vehicle vibration and measured the static and dynamic parameters and microstructure of different moisture content and structural loess.On the basis of this,the paper reveals the disaster mechanism of loess highway slope.The main conclusions drawn are as follows:(1)The main failure types of loess highway slope are mainly landslide,collapse and exfoliation,in which exfoliation can be subdivided into strip exfoliation,scaly exfoliation,flake exfoliation,honeycomb exfoliation,wedge exfoliation and mixed exfoliation.The slope disaster is mostly shallow surface destruction,the scale is small,mainly occurs in the spring and summer,most of which distribute the plane with the protruding road bends;The collapse mainly develops in the slope crest;The exfoliation distributes in the slope toe or the middle slope.(2)The vibration response of the slope augment with the increase of the vehicle load,and the vibration response of the concave slope and the cutting slope is the strongest.The position of the strongest vibration response in different slopes is different: the position of linear slope is the turning end near the road;the position of concave slope is located near the foot of the slope,and the position of terrace slope is the secondary slope near the highway,and the position of double sided slope is located in the middle of the slope near the side of the road;In the the cutting slope,the X-directional wave near the concave slope toe is strong and the Z-directional wave near the convex slope toe is strong.The strong position of vibration response is prone to failure of slope instability,which is consistent with field investigation.(3)Under static condition,with the increase of water content,the inner friction angle of loess decreases,and at first the cohesion force increases and then decreases.Under the dynamic condition,with the increase of water content,the mechanical index of soil decreases drastically.Compared with static test,the internal friction angle increases when the vibrations are 2000 times and decreases when 5000 times,and the cohesive force augments with the increase of the frequency of vibration.(4)The vibration deformation of natural loess is larger than that of saturated loess,and the more the pore is,the more possible vibration deformation fail.Under the condition of low water content,,the loess will form micro-fissures along the weak joint,and then develop into macroscopic cracks with the action of static and vibration,but the cracks are more under the action of vibration,which indicates that the shallow surface loess under the vehicle vibration is easy to be crushed to form a potential unstable block.With the increase of water content,the structure of soil is weakened or destroyed,and the position adjustment of the loess grains that’s macro performance is bulging will occur under static and dynamic action.(5)The slope shape and the loess type are the decisive factors of slope stability,and the structural damage and the strength attenuation caused by vehicle vibration and the interaction with the rainfall is the main inducing factor of slope deformation failure.The research of this problem has lots of theoretical and practical significance for revealing the failure mechanism of loess Highway slope and protection.