Experimental Study On The Characteristics Of Sulphate Saline Soil Solidified With Lime And Fiber

Ningxia is located in the cold and arid region in the northwest of China,its central arid zone has a large temperature difference between day and night,high groundwater mineralization,little rainfall and high evaporation,which leads to serious soil salinization in the region under this special climate characteristic,and mainly sulfate saline soil.Due to the influence of environmental temperature,the sulfate saline soils will show the characteristics of salt-freeze swelling,corrosion and solution,which will cause the soil structure damage and strength reduction,thus making the foundation of buildings damaged and seriously endangering the safety of buildings.In this thesis,lime and Polypropylene fiber are used as solidified materials to study the effect of lime content,fiber content,fiber length and salt content on the mechanical property of solidified sulfate saline soils,and freeze-thaw cycle tests of lime-fiber solidified sulfate saline soils and lime soils are also carried out to study the strength deterioration law after freeze-thaw cycles.On this basis,the introduction of on this basis,the Weibull probability density function was introduced to establish the strength deterioration model after freeze-thaw cycles.With the help of scanning electron microscope(SEM)test,the mechanism of fiber on the strength of solidified sulfate saline soil was revealed,and the relationship between strength and porosity was described by ImageJ image processing analysis.The main research results obtained are as follows:(1)The unconfined compressive strength test based on fiber solidified sulfate saline soil showed that the solidified effect was better when the fiber length was 12 mm.With the increase of fiber content solidified soil the compressive strength showed a trend of increasing and then decreasing,and reached a peak at 0.3%fiber content,compared with the soil without fiber,the strength of the soil with fiber is obviously improved,with the increase of salt content solidified soil strength showed a trend of increasing and then decreasing,and reached a maximum at 2%,solidified soil strength increased with the increase of lime content.(2)Grey correlation analysis shows that the effects of salt content fiber content and lime content on the strength of solidified soil is lime content,salt content and fiber content in descending order.(3)The mass loss rate of lime-fiber solidified soil and lime solidified soil gradually increased with the increase of freeze-thaw cycles,and the mass loss rate of lime solidified soil was greater than that of lime-fiber solidified soil.The strength deterioration coefficient of the two solidified soils gradually increases with the increase of the number of freeze-thaw cycles at different freezing temperatures,and the deterioration coefficient of the lime soil is greater than that of the lime-fiber solidified soil,the strength of the solidified soil gradually decreases with the increase of the number of freeze-thaw cycles,and the strength of the lime solidified soil decreases at a greater rate than that of the lime and fiber solidified soil,with the greatest decrease in strength at-10℃.(4)Based on the Weibull probability density function to simulate the relationship between the number of freeze-thaw cycles and the degree of deterioration of soil strength,a mathematical model was established for lime solidified soil,of lime-fiber solidified soil at different numbers of freeze-thaw cycles and the deterioration coefficient of soil strength,and through comparison with the measured results,the model can better reflect the deterioration law of solidified soil strength with the number of freeze-thaw cycles.(5)Scanning electron microscopy(SEM)tests showed that the fractal dimension of the solidified soil increased with the number of freeze-thaw cycles,and the fractal dimension of the lime solidified soil was larger than that of the lime-fiber solidified soil.Meanwhile,ImageJ image processing analysis also showed that the porosity of the solidified soil increased gradually with the number of freeze-thaw cycles,and the porosity of the lime-fiber solidified soil was smaller compared with that of the lime soil.