Study On Liquefaction Properties Of Saturated Sand Under Different Drainage Conditions And Silt Soil Interlayers

China is an earthquake-prone country.The liquefaction issues of sand caused by earthquakes have been one of the key and hotspots in the geotechnical engineering.At present,the research on the influencing factors and influencing mechanism of sand liquefaction have acquired many achievements and get widely recognized.Under the action of the earthquake ground motion,excess pore water pressure will occur in the soil.And the actual formation of the soil at different locations by the adjacent soil permeability of the impact that led to the different drainage conditions.Drain conditions have a certain effect on the produce diffusion,transfer and redistribution of pore water pressure.However,at present,most researches on liquefaction problems are assumed as undrained conditions;the effect of actual drainage conditions on soil liquefaction characteristics has not been fully studied.Based on this,the liquefaction characteristics of saturated sand under different drainage and silt interlayer are studied by three axle tests in this paper.(1)This paper designed a drainage sandwich device that could control the permeability coefficient.The device was placed at the top of the specimen to achieve control of the sample different drainage conditions.It provide the basis for the follow-up test.Under biaxial loading,the specimen had a large deformation and a rapid development of pore water pressure,and the higher the liquefaction strength of the specimens.(2)Three axle tests of saturated sand under different drainage conditions was carried out by dynamic triaxial apparatus and analyzed the test results under different drainage conditions.The influence rule of pore water pressure and stress-strain were also summarized.Test results showed that with the increase of permeability ratio,the pore water pressure of specimens increases rapidly,the effective stress decreases slowly,and the smaller the deformation is,the higher the liquefaction strength of specimens.(3)The dynamic three axle tests of saturated sand under the condition of silty interlayer were carried out,and the relation between the development of excess pore water pressure and stress-strain curves of saturated layered sand samples with different interlayer spacing ratio and different drainage conditions was obtained.Test results showed that: the saturated pore water pressure accumulation rate of saturated layered sand sample decreases with the increase of interlayer spacing ratio,and the liquefaction resistance of specimens increases.The effects of drainage and biaxial loading on the liquefaction strength of saturated layered sand samples were similar to those of homogeneous sand samples.The excess pore water pressure developed faster under the condition of large permeability coefficient and biaxial loading,and the sample was easier to liquefy.(4)The shear tests were carried out after liquefaction of saturated sand samples,and the dissipation and deformation curves of excess pore water under different drainage conditions were obtained after liquefaction.Test results showed that: the shear modulus of the saturated sand sample after liquefaction increases with the increase of permeability coefficient.That is,the increase of the drainage condition increases,the corresponding volume of the sample after liquefaction decreases,and the shear absorption effect was enhanced.