Experimental Study On Static And Dynamic Characteristics Of Saturated Sand Considering Initial Fabric

The soil will form a different internal structure due to its sedimentary environment and conditions.The macro mechanical properties of materials depend on the microstructure of the material inside.The anisotropy and nonlinearity of soil are the macroscopic reflection of the change of soil structure elements.For sand,the arrangement and direction of particles are mainly studied,namely the fabric.In the natural conditions of deposition,influenced by gravity,the long axis direction close to the level,while on the road backfill case,the particles are arranged out of order because of the suction induced by certain moisture in sand.The same sand has different fabric,which means different mechanical properties.At the same time,sand is used widely as the foundation material,need to bear the traffic load,wave load,seismic load and so on.These loads will not only cause the change of the principal stress,but also the deflection of the stress axis.Under the traffic load,the roadbed soil will produce the bigger subsidence deformation,resulting in pavement cracking and other diseases.The seismic action will lead to liquefaction of sand,resulting in lower strength of sand.Therefore,it is very important to study the influence of initial fabric on the mechanical properties of sand under the above complex stress path.In the present study,sand specimens with different initial fabric were prepared in the laboratory by dry deposition(DD)method and moist tamping(MT)method.The hollow cylinder apparatus was used to carry out the experimental study on the Toyoura sand under different stress paths.The mechanical properties of sand under directional shear,pure stress principal axis rotation and cyclic loading stress path are mainly studied.The effect of initial fabric on the deformation,strength and non-coaxial characteristics of sand is analyzed by directional shear test.Under the partly change of the average principal stress p,deviatoric stress q and intermediate principal stress coefficient b,Effect of initial fabric on deformation characteristics,dilatancy,shear modulus and non coaxial characteristics is studied by pure stress principal axis rotation test.Cyclic loading test is investigated in the influence of initial fabric on axial deformation and volume strain under the respectively change of the average principal stress p,cyclic stress ratio CSR and cyclic torsional shear stress ratio ?.A prediction model of axial cumulative strain is established.