Study On Dynamic Characteristics Experiment And Slope Stability Of Expansive Soil

The expansive soil has been regarded as one of major threats to engineering due to its characteristics of water-swelling to soften and dehydration-shrinking,and slope instability is one of the threat forms.In recent years,more and more attention is paid to the dynamic stability of expansive soil slope because of frequent earthquakes.In this paper,the expansive soil of Nanyang section of the middle route of the South-to-North Water Diversion Project is studied.The influence of initial deviator stress,the phase difference of multi-direction loading and the transverse wave and OCR on the dynamic characteristics of expansive soils are analyzed by the dynamic triaxial test,and the numerical simulation method is used to study the dynamic response characteristics of the slope.The following conclusions are obtained:(1)The dynamic shear modulus and damping ratio of the expansive soil are in accordance with the basic laws of the general clay.The dynamic shear modulus decreases with the increase of the strain,and the damping ratio increases with the increase of the strain.The Hardin-Drnevich model in the viscoelastic theory is better for fitting the test points.(2)The amplification effect of the initial deviatoric stress on the Gmax is up to 176.9%,which is much higher than 128.3%,which is the maximum amplitude of the phase difference,and the coupling effect on Gmax is quiet significant.The initial deviator stress has an amplification effect on the damping ratio of the expansive soil,and the damping ratio decreases slightly with the increase of the phase difference,and the empirical formula used in D~G/Gmax curve of expansive soil has good fitting effect.(3)Under the same confining pressure,when the OCR is larger,the dynamic shear modulus and damping ratio are also larger,and with the increase of strain,the influence degree gradually decreases,and the dynamic shear modulus tends to be near the same stable value.At the same strain level,the dynamic shear modulus and damping ratio are also larger when the confining pressure is larger.With the increase of OCR,the maximum increase of Gmax is about 45%.With the increase of confining pressure,the Gmax increases gradually,the maximum increase is about 95%,and the minimum damping ratio Dmin increases slightly with the increase of the ratio of over consolidation.(4)With the increase of OCR,dynamic cohesion of cd decreases,the maximum attenuation rate of 29.67%;the dynamic friction angle of φd increases,the maximum increase is up to 105.36%.The dynamic shear stress amplitude-dynamic shear strain amplitude curve of expansive soil is characterized by three stages,and the curve shape is approximately the same.The application of limit equilibrium theory to the analysis of soil stage under cyclic loading is quite well.(5)The type of seismic damage of the ideal homogeneous expansive soil slope is similar to that of the ordinary soil slope.The potential damage surface is arc-shaped,and the maximum horizontal displacement is located in the middle of the slope.From the time curve,the stress amplitude of the slope foot is the highest.The displacement,velocity and acceleration are the highest in the middle of the slope.Under the same condition,the horizontal displacement decreases with the increase of the phase difference,and decreases with the increase of OCR.