Experimental Study On Dynamic Characteristics Of Silty Sand In The Yellow River Flood Area By Traffic Loading

Traffic loading is a common form of load in actual road engineering and is closely related to our daily lives.A large amount of research shows that the subgrade soil will cause continuous rotation of the principal stress axis under traffic loading,which will have a great influence on the strength and deformation characteristics of the soil.As a national transportation hub,Henan province contains a large amount of silty sand in the Yellow River flood area.Due to the poor stability of this soil,engineering safety problems are easy to occur under the action of traffic loading.In this paper,GDS hollow cylinder apparatus is used to simulate the stress path under traffic loading,including heart-shaped stress path and circular stress path.The drainage conditions are kept unchanged during the test.The influences of four factors including cyclic stress ratio,torsional shear stress ratio,effective confining pressure and loading frequency on the dynamic characteristics of saturated silty sand are studied,which can provide reference for practical engineering.The main content of this paper is as follows:(1)In order to simulate the actual working conditions,dynamic tests under conventional triaxial stress path and heart-shaped stress path were carried out considering the condition of continuous rotation of the principal stress axis.The influence of continuous rotation of the principal stress axis on the dynamic characteristics of saturated silty sand was discussed,and it was revealed that the cyclic stress ratio and the torsional shear stress ratio can accelerate the accumulation of bulk strain and axial strain.The development trend of volume strain and axial strain is different under different stress levels,effective confining pressure and loading frequency.(2)Based on the Monismith index model,the prediction model of axial plastic cumulative strain of saturated silty sand under the heart stress path was proposed,and the model was used to predict the development trend of axial plastic cumulative strain under different cyclic stress ratios and torsional shear stress ratios when the effective confining pressure was 150 k Pa and the loading frequency was 0.5 Hz.The results show that the model is suitable for the cumulative deformation prediction of saturated silty sand.(3)The development law of elastic modulus and shear stress-strain relationship of saturated silty sand under the heart-shaped stress path are analyzed.The results show that the change of cyclic stress ratio and torsional shear stress ratio can affect the development trend of elastic modulus and hysteresis curve.The shear modulus ranges from 20 MPa to 80.7MPa,and the development law of the shear modulus is basically the same under different test conditions,but the shear modulus is larger under higher torsional shear stress ratio.(4)The development law of axial strain and resilience modulus of saturated silty sand under circular stress path is studied,and the deformation characteristics of saturated silty sand under circular stress path and heart-shaped stress path are compared.At the same time,the exponential model proposed above is used to predict the axial plastic cumulative strain of the sample under the circular stress path,and the predicted results are close to the actual results.