Effect Of Temperature On Shear Strength And Deformation Characteristics Of Non-frozen Saline Soil

Shear strength and deformation characteristics are important contents in unsaturated soils.At the same time,these are also hotspots and difficulties in geomechanics research at home and abroad.In practical engineering applications,due to the complexity of its impact,accidents and problems appear more common.In order to clarify the effect of temperature caused by freezing temperature and crystallization difference on the shear strength and deformation characteristics of saline soil.Carry out research and draw conclusions from the following aspects.First of all,three types of saline soil from Qarhan-Germu Expressway with a salt content of 10%to 36%were selected as test specimens;high chloride content of chloride salt specimen(HC-1);low content of sulfate salt specimen(HC-2);and higher sulfate content with lower chloride content salt specimen(CS).Prior to testing,a freezing temperature test was conducted on the CS specimen where the temperature was lowered to-20?.The CS specimen has the lowest salt content verifying that all three selected saline soil specimens(HC-1,HC-2 and CS)will not freeze when the temperature is lowered to-20?.Secondly,according to the results of the direct shear tests of the above soil samples at five different controlled temperatures(-20?,-10?,0?,+10? and+20?),the expressions of the relationship between the temperature and the shear strength parameters of the three types of saline soils were summarized respectively.The influence of temperature on its shear strength and Young's elastic modulus was analyzed,and the formula of shear strength and tangent Young's modulus of saline soil under the influence of temperature was established by numerical fitting.The test results indicate that the shear strength and initial tangent Young's modulus of the three types of saline soil increase and tend to the peak as the temperature decreases from+20? to-10?.The HC-1 and HC-2 soil specimen exhibits a downward trend when the temperature continue to decrease to-20? while the results of the CS soil specimen tended to be stable.For saline soils of different salt types,the effect of temperature on the destruction ratioR_f is also different.During the temperature drop from 20? to-20?,the HC-1 soil destruction ratioR_f peaked at-10?.Under the lower load(100 kPa),it shows the characteristics of increasing first and then decreasing.Under higher loads(200 kPa,300 kPa,400 kPa),it shows the characteristics of increasing first and then decreasing slowly.The CS destruction ratioR_f exhibits three segmental changes in the temperature range of20??10?,10??-10? and-10??-20?,respectively,first increasing,then tending to Smooth and finally reduced.In addition,according to the freeze-thaw cycle low temperature triaxial test and deformation test results of two soil samples(HC-1,CS)in the temperature range of+20? to-20?,analysis of the effects of unfreezing and thawing cycles on the deformation characteristics and shear strength of saline soils.The test results show that when the freeze-thaw cycle of HC soil samples proceeds to the fourth cycle and the freeze-thaw cycle of CS soil samples to the ninth cycle,the saline soil soil samples enter a new equilibrium state.The effect of freeze-thaw cycles on CS damage ratio is greater than that of HC-1 soil samples.Freezing and thawing cycles have a great effect on the soil deformation characteristics and shear strength of the two test soil samples(HC-1,CS),and their k value trends are also inconsistent.The relationship between the k value of HC-1 soil sample and CS soil sample has a strong exponential decay function relationship with the number of freeze-thaw cycles.Finally,based on Duncan-Chang model theory,this paper proposes the expression of Young's modulus of elasticity of non-frozen saline soil affected by temperature.The 9deformation parameters included in the model can be determined by experiments,which can fully describe the mechanical characteristics of non-frozen saline soils.At the same time,this can be regarded as the application and extension of Duncan-Chang model in the mechanical properties of non-frozen saline soil.