Experimental Study On The Effect Of Initial Fabric On Static And Dynamic Behavior Of Saturated Clay

The displacement and deformation of soil are mainly caused by the change of internal structure of soil,and the difference of internal structure played an important role in the change of soil engineering characteristics.Soil composition,stress history,the current state and the environment have an important influence on the formation of soil structure.The solid with different types structure in the river estuary,soft foundation treatment and engineering solid waste treatment.The soil structure includes the fabric and connection between particles.In the past,there was less consideration of the influence of the fabric in the study of the structure of clay.Therefore,the effect of initial fabric on the static and dynamic behaviors of clay were studied by preparing different fabrics samples.The methods of preparing remolded soil samples are summarized.A vacuum suction device has been developed to achieve a rapid preparation of a batch of clay specimens with good uniformity and high repeatably.The preparation of flocculated and dispersed soil samples were realized by means of changing the pore fluids.After vacuum freeze drying,microscopic scanning tests were carried out to verify the microstructure of two kinds of soil samples.The consolidation permeability,compression and consolidation undrained shear tests were carried out for two kinds of fabric soil samples.The results show that the permeability coefficient of flocculated samples is obviously larger than that of dispersed samples,and the difference of consolidation pressure decreases gradually with the increase of the pressure.The different of compression index between different fabric soils is great,while for the swelling index is little.It may be because of the larger pressure changed the arrangement of particles.In triaxial shear,the dispersed samples have higher strength and greater stiffness.Dispersed samples present stress-strain softened,while the flocculated samples are strainstabilized or slightly hardened.The effective stress path and the critical state line of the two kinds of soil samples are obviously different,and the soil sample of the flocculated samples show a larger shear contraction.One-way cyclic compression test was carried out on two kinds of fabric soil samples.The result shows that different fabric soil samples have different critical cyclic stress ratios.When the stress level is less than the critical cyclic stress ratio,the pore pressure and axial strain of the soil sample of the flocculated samples are larger than dispersed samples.When the stress level is greater than that,the dispersed samples are abruptly destroyed and the flocculated samples are gradually destroyed with higher strength.When the cyclic stress ratio is 0.35,the degree of hardening of the flocculated is larger than that of the dispersed samples.With the increase of cyclic stress ratio,the softening index is less than one.The softening degree of the dispersed samples are larger than the flocculated.After cyclic loading,the soil mass produced positive pore pressure and appeared different degree of over consolidation.The quasi over consolidation ratio increased with the increase of cyclic stress ratio.Under the small cyclic stress,there is little effect on the undrained strength of the two kinds of fabric soil samples.Under the larger cyclic stress,the strength of the flocculated samples had higher strength and smaller pore pressure,even the negative pore pressure with the heavy over consolidation occurs.