Experimental Research On Deformation Characteristics Of Sand Under Naturally Drained Condition

The fluidity of sandy soil caused by earthquake has long been an important and hot topic of geotechnical engineering study. During an earthquake, excess pore water pressure can arise in soil mass. If the hydraulic conductivity of soil varies significantly across different layers, the pore water will gather, infiltrate and then accumulate locally in soil during the spread, transfer, and redistribution of excess pore water pressure. The soil in this region will be loosened after absorbing water. Meanwhile, under the influence of earthquake-induced shear stress, the slope constructed of dilatant sandy soil will undergo flow, large deformation, and even destabilization after an earthquake. To study the flow and large deformation of structures made of dilatant sandy soil after earthquake, an investigation needs to be conducted into the spread, transfer, and redistribution of excess pore water pressure in a real boundary value problem and the local water absorption by soil during this process. Moreover, the deformation characteristics of saturated sandy soil experiencing forced water absorption, especially its dilation at a constant ratio of initial isogonal stress to current peak stress, need to be described correctly.This study is summarized as follows:(1) The triaxial test apparatus was modified and upgraded into a set of apparatus for the simulation of water absorption of saturated sandy soil through a flow-slide stress path. The validity and reliability of the apparatus upgrade was demonstrated by conducting a verification test.(2) An experimental plan was designed to study the characteristics of sandy soil deformation in different drainage conditions. A series of physical and static tests were carried out to obtain the mechanical properties of sandy soil and provide a basis for the selection of parameters for following triaxial test.(3) A triaxial test was conducted in different drainage conditions:full drainage, no drainage, and water absorption through a flow-slide stress path. The results indicated that the stress paths and deformation characteristics observed in full drainage and no drainage conditions were different from those of soil experiencing water absorption through a flow-slide stress path.(4) Tests were conducted to investigate the influences of relative compactness, initial consolidation stress, and initial isogonal stress on the flow-slide paths of soil after water absorption and results were analyzed in depth. The characteristics of the variation in the stress path, confining pressure, isogonal stress, shear stress ratio, and volume change were summarized based on the test results.① The relative compactness of soil had influences on the following aspects:the slope of stress path during the flow-slide failure stage; the rate of confining pressure decline in the initial stage of flow-slide failure; the pattern of shear stress ratio curve; the volume change of soil after absorbing water. The isogonal stress was not affected by soil’s relative compactness.② The initial consolidation stress had a small effect on the soil’s volume change and nearly no effect on other parameters.③ The initial isogonal stress had influences on the following aspects:the isogonal stress at the initial stage of flow-slide failure in the stress path and the position of soil in the shear failure line during the flow-slide failure stage; confining pressure in a stable state; and the initial and final isogonal stresses. The initial isogonal stress had a small effect on soil’s volume change and little effect on the shear stress ratio.