Study On Mechanical Test And Microstructure Characteristics Of Silicified Solidified Loess

With the rapid development of China ’s economy,the speed of infrastructure construction in the western loess area is accelerating.Due to its special topography and engineering geological conditions,the loess needs to be improved and reinforced during engineering construction.At present,the study of silicification method shows that single-liquid silicification and double-liquid silicification have good results in improving loess strength,enhancing soil cementation performance and reducing soil compressibility,but the influence of water content on its performance is rarely studied.Based on the above background,this study selected the loess of a foundation in Beilin District of Xi ’an as the research object,with 5 %,15 %,25 % water content as the test conditions,water glass and water glass-calcium chloride as curing additives.The compression test,triaxial test,particle analysis test and electron microscope scanning test were carried out on the samples.The macroscopic mechanical properties and fine microstructure parameters of the early performance were analyzed,and the effects of macroscopic and fine microstructure under different water content were evaluated.It provides theoretical support for the application of silicification method in loess area under different water content.The main research results are as follows :(1)Confined compression and consolidation tests under different water contents(5 %,15 %,25 %)were carried out on uncured loess,single-liquid and double-liquid silicified solidified loess.The compressive stress-strain relationship of soil was compared and analyzed,and the e-p curve,e-lgp curve and the variation characteristics of compression coefficient and compression modulus were obtained.Hyperbolic model and power function model were used to fit the compression test results of soaking loess.It was found that the fitting effect of hyperbolic model was better than that of power function model under different water content and different curing methods.(2)Triaxial tests were carried out on uncured loess,single-liquid and double-liquid silicified loess under different moisture contents.The stress-strain curves of three kinds of soil samples were strain hardening curves,and the shear strength of three kinds of soil samples decreased with the increase of moisture content.Under the moisture content of 5 %and 15 %,the curing effect of single-liquid silicification method was better than that of double-liquid silicification method.The stress-strain curves of three soil samples under different water contents are fitted by Duncan Chang model,and the corresponding parameters are obtained.(3)Scanning electron microscopy tests were carried out on uncured loess and single-liquid and double-liquid silicon-cured loess under different water contents.The results showed that the single-liquid silicification method mainly filled the pores between loess particles and cemented fine particles,while the silicate colloid in the double-liquid silicification method increased the surface or edge contact of the particles and formed agglomerates with denser structure and larger particle size.With the increase of water content,the cementation gradually becomes worse,resulting in increased compressibility and decreased strength.The silicification method makes the proportion of large and medium pore area in loess decrease and the proportion of small and micro pore area increase.