Experimental Research On Dynamic Properties Of Disturbed Loess

Loess in China mainly distributes in the central and western regions, where earthquake happens frequently. Since loess has strong seismic vulnerability, so it is quite important to study the dynamic characteristics of the soil in loess area.Road and railway embankments, building foundations soil replacement cushion, and loess embankment which is widely used, belong to disturbed soil problem, some of the engineering belong to the freeze-thaw conditions in cold regions, the design and construction must consider the dynamic problem. This article analyzes variation of disturbed loess dynamic characteristics under cyclic loads, which will change with the diversification of water content, confining pressure and the vibration frequency through dynamic triaxial tests. Further soil dynamic characteristics after freeze-thaw cycles are studied.Research results are as follows:Disturbed loess dynamic stress-strain relationship is hyperbolic.The same dynamic shear strain corresponding to the dynamic shear stress and dynamic shear modulus increases with confining pressure and vibration frequency increasing, as the water content decreasing. Through the exponential function of G₀～wfitting under different confining pressures, and the relationship curve normalized, the equation of G₀/σ_m^1/2～w sw is established, which can forecast the maximum dynamic shear modulus in the case of the same soil in the same test conditions. Damping ratio of disturbed loess tends to increase with dynamic shear strain and water content increasing.Damping ratio of disturbed loess shows no significant law with the confining pressure and the frequency of vibration increasing.The dynamic strength parameters of disturbed loess will decrease with soil water content increasing. Under the same water content, the dynamic strength parameters of disturbed loess will increase as the vibration frequency increases. The increasing trend will be more obvious with water content increasing.After freeze-thaw cycling, disturbed loess dynamic stress-strain relationship emerges hyperbolic distribution only in a small thaw cycle number. With the increasing number of freeze-thaw cycles, dynamic friction angle decreases, cohesion increases; dry density of the soil gradually reduces. Compared with the soil not frozen-thaw,the maximum dynamic shear modulus of soil frozen-thaw decreases, but with the increasing number of freeze-thaw cycle, the maximum dynamic shear modulus will not always reduce.