Study On The Engineering Properties And Constitutive Model Of Saline Soil

Saline soil is a kind of special soil.It has a huge negative impact on engineering and human activities.The solution of this problem requires the thorough study of saline soil.Based on the saline soil literature research,this paper focuses on the shortcomings of existing research.Targeted at sodium chloride saline soil and sodium sulfate saline soil,the engineering properties and constitutive models of this two kind saline soil were studied.?1?The basic engineering properties of saline soil were investigated by limit moisture content test,compaction test and direct shear test.Liquid limit,plastic limit and plastic index of sodium chloride saline soil decreased with the increase of salt content,and the liquid limit of sodium sulfate saline soil increased first and then decreased,the plastic index decreased and the plasticity index increased.After adding salt,the optimal moisture content of NaCl saline soil decreased continuously,while the optimal water content of sodium sulfate soil increased first and then decreased.The above two indexes of sodium sulfate saline soil were all higher than those of NaCl saline soil under salt content.The direct shear test was carried out for the 9 samples under the condition of their own optimum water content and maximum dry density.The results showed that the cohesion of the sodium chloride saline soil decreased with the increase of salt content,and the cohesion of sodium sulfate decreased.The internal friction angle of the two saline soil increased first and then decreased with the increase of salt content.?2?Through the self-made soil column test,the permeability and microstructure of soil samples were studied under the capillary action of different salt solution.Under the action of capillary water in salt solution,the salt content rises with water,and the concentration of salt is higher and the concentration of salt is more obvious in the middle and lower part of the soil column.The blockage effect of the pores and the effect of the soil particles resulted a decreasing of the total pore volume.The permeability coefficient is more obvious.With the increase of salt solution concentration,the effect is more obvious;the salt solution concentration used in No.1 soil column is the concentration of salt solution.The property of the upper soil sample is close to the original soil sample,and the permeability coefficient of the bottom specimen of No.3 soil column has an obvious change,which is2.94×10^-9cm/s.The salt solution has a significant effect on it.?3?The analysis of the Cambridge model and the modified Cambridge model was used to demonstrate the feasibility of modified Cambridge model for saline soil research.It is find that the key to apply this model to saline soil is to establish the relationship between M,?,?and salt content.The consolidation test and Consolidated Undrained Shearing test of sodium chloride saline soil and sodium sulfate saline soil were carried out,from which the rebound coefficient,compression coefficient,cohesive force and internal friction angle of saline soil are obtained.Those dates were used for the establishment of saline soil modified Cambridge model suitable.The Nash-Sutcliffe efficiency coefficient?NSE?was used to measure the deviation between the calculated value and the experimental value of the model,and to evaluate the credibility of the model.For samples with water content of20.5%and dry density 1.70g/cm³,the model has a high reliability and a NSE of 0.90¹,For other samples,the reliability of the model is slightly lower,and the NSE is 0.65⁰.85generally.