Experimental Study On Wet-Seismic Dynamic Characteristics Of Loess

In this paper,a new dynamic single-shear instrument is used to carry out dynamic test research on undisturbed loess.The effects of water content and compressive stress on the dynamic stress-strain relationship,dynamic shear modulus,damping ratio and dynamic strength of undisturbed loess were studied,and the empirical formulas of dynamic shear modulus and damping ratio were obtained.The effects of changes in physical properties,static conditions and dynamic conditions on the deformation of the Lanzhou loess earthquake were analyzed,and the empirical formula of the structural coefficient of the earthquake loess was established.Then the humidification-seismic deformation characteristics of the loess under certain conditions were studied.This article draws the following conclusions:(1)The dynamic stress-dynamic strain curve of loess conforms to the hyperbolic function.The dynamic shear stress increases nonlinearly with the increase of dynamic shear strain,and eventually tends to be gentle.The greater the water content,the lower the curve;the greater the compressive stress,the higher the curve.(2)The dynamic shear modulus of loess decreases nonlinearly with the dynamic shear strain.Moisture content and compressive stress have significant effects on the dynamic shear modulus.Finally,an empirical formula for the dynamic shear modulus change with compressive stress,configuration and dynamic shear strain in the Hardin-Drnevich hyperbolic model is finally established.(3)The curve of loess's damping ratio with shearing strain shows an upward trend.The higher the water content,the greater the damping ratio;the effect of compressive stress on the damping ratio is not obvious.(4)The dynamic strength of the loess decreases with the increase of the vibration order.Dynamic strength decreases with increasing water content and increases with increasing compressive stress.(5)The changes of physical conditions,static conditions and dynamic conditions have obvious influences on the loess seismic deformation.The seismic subsidence coefficient increases with increasing water content,vibration order,and dynamic shear strain anplitude,and decreases with increasing compressive stress.Based on this,anempirical formula for the seismic subsidence coefficient of structured loess under the influence of compressive stress,structure,vibration order and shear strain amplitude is established.(6)Under the same humidification condition,the total wet-seismic deformation of the loess increases with the increase of compressive stress.At the same dynamic shear strain,the total wet-seismic deformation of the loess increases with the increase of the vibration order;at the same vibration order,the total wet-seismic deformation of the loess increases with the increase of the dynamic shear strain.(7)Under the same compressive stress condition,the total wet-seismic deformation of the loess decreases with the increase of the structural degree.At the same dynamic shear strain the total wet-seismic deformation of the loess increases with the increase of the vibration order;at the same vibration order,the total wet-seismic deformation of the loess increases with the increase of the dynamic shear strain.