Study On Dynamic Characteristics Of Fine-grained Saturated Sand Under Complex Stress Path

The dynamic characteristics of sand under dynamic load have always been the focus of academic and Engineering community.At present,there are many studies on the dynamic characteristics of pure sand,but the sand in the project often contains fine particles,Its dynamic characteristics under complex stress paths such as wave loads are still unclear.In order to enhance the understanding of related problems,this paper uses Hollow Cylinder Apparatus(HCA)to study the dynamic characteristics of sand with different fines content by three kinds of stress paths:dynamic triaxial,dynamic torsional shear and circular coupling.The main conclusions are as follows:(1)The stress path has a significant effect on the pore pressure growth law and the liquefaction week(Nf).The pore pressure development curve of the dynamic triaxial and dynamic torsional shear stress path test can be divided into three stages,the first stage develops faster,the second stage grows steadily,the third stage rapidly increases to liquefaction;The pore pressure development curve of the circular coupled stress path loading test grows linearly before failure,and the pore pressure increases rapidly near the failure.The Af of the circular coupled stress path test is smaller than the djmamic triaxial and dynamic torsion shear.(2)In the circular coupled stress path loading test,the rotation of the principal stress axis causes the accumulation of plastic strain;when the stress state of the sample is close to the triaxial stretching,the plastic strain increases more obviously.(3)The relationship line between the fine particle content(FC)and the liquefaction cycle is a parabola whieh is opening upward,and the FC eorresponding to the lowest point of the parabola is the threshold FCm.When FC<FCm,Nf decreases with the increase of fines content FC;while FC>FCm,Nf increases with the increase of fines content FC,and the FCm of the sand materials used in this test is 10%.In the circular coupled stress path loading test,when the FC is less than 10%,the normalization law of the pore pressure of the sand is similar to pure sand;when the FC is greater than 10%,with the increase of FC,the normalized curve of pore pressure of sand shows a law close to the pore pressure of clay.(4)The fitting parameters of the circular coupling are related to the fine particle content,the cyclic stress ratio,and the relative compactness.Unable to use the same fit curve for the circular coupling.(5)The larger the initial effective confining pressure,the larger the corresponding dynamic modulus;the larger the FC,the smaller the corresponding dynamic modulus;the influence of FC and initial effective confining pressure on the dynamic modulus normalization curve can be ignored;The larger the effective confining pressure,the smaller the normalized damping ratio,and the normalized damping ratio of the fine-grained sand is more affected by the initial effective confining pressure than the pure sand.