Experimental Study On Engineering Properties Of Lop Nor Saline Soil In Condition Of Freeze-thaw Cycle

Through the spot investigation,choose the samples and the density test, natural water contenttest,particles distribution test,soluble salt test, liquid and plastic limit test under different leveldesalinization and penetration test under different freeze-thaw cycles,through the test above,study on thebasic physical properties of Lop Nor saline systematically.Experiental results indicated that: within thescope of depth at0.2m to2.0m, the natural density increases with increasing depth,the presence of thecrystalline salt increase the natural moisture content of the saline soil, the saline soil in the region is mainlycomposed of fine-grained sand saline soil,by the standard of saline soil classification,the saline soil in thisregion mainly is chlorine saline soil and sulphate saline soil which contain the salt is higher,mostly isultra-strong saline soil and the salt content reducing with the depth in the range of0.2m to2.0m.The testresults show a linear relationship between soluble salt content and the conductivity in this region, the testresults indicated that the liquid and plastic limits of chlorine saline soil and sulphate saline soil increasewith decreasing salt content. When the saline soil sample through3-5freeze-thaw cycles, the permeabilitycoefficient increased significantly, with the increase in the number of freeze-thaw and the penetration timeto reach a certain, the soluble salts in saline soil reduced and permeability coefficient not significantlyincrease.Select the typical natural strong chlorine saline soil sample, conduct unconsolidation undrained triaxialtest.Experiment show that:strong chlorine saline soil shear strength parameters of cuwith the increase infreeze-thaw cycles show a decreasing trend,the within friction angle ushow a slightly increasing trend,But the extent is marginallyIn the consolidated and drain conditions, cohesion strengthc ddecreases with increasing freeze-thawcycles, the internal friction angle decreases gradually with the freeze-thaw cycles of the two different drydensity sample, the reduced amplitude of internal friction angle dat smaller dry density sample.At thelarger dry density of no freeze-thaw, the stress-strain curve display softening type at small confiningpressure,with the number of freeze-thaw cycles increasing,the stress-strain curve gradually realized thestrain hardening type of the two dry density sample,at the same number of freeze-thaw cycle and the samedry density,the initial modulus increasing with confining pressure increases,the incremental tangentmodulus decrease with confining pressure increases.Rfslightly increased with the increase in the numberof freeze-thaw cycles and K is slightly lower in the Duncan-Chang E-μ model parameters.