Study On The Effect Of Gypsum On Strength Of Loess In Tongxin District Of Ningxia

Loess is a kind of special soil, and its structure and moisture are typical characteristics. Ningxia is the main area of loess distribution in China. Loess soil layer thickness is large, the vertical joint development, soluble salt content is high, especially in the soluble salt gypsum content is high. The composition of the particles is mainly dominated by silt, the soil is loose, the structure of the large pore is obvious, the structure and the self weight are strong. The pore structure is obvious, the structural weight and wet collapsibility is greater. A large number of civil engineering, water conservancy and transportation engineering projects are build on loess, and the safety of the engineering foundation construction is closely related to the strength of loess. The study on the effect of soluble salts on the strength of loess and the mechanism of its understanding is not unified. It is very necessary to study the effect of salt solution on the strength of loess.The article takes the Ningxia concentric loess as the object, gypsum content, soluble salt CaCl2, Na2SO4 and NaCl content, dry density, water content and age as factors, Lg(34) and L16(45) orthogonal test scheme are designed to respectively study the effect of gypsum on the strength of loess and the thixotropy of loess strength using automatic triaxial instrument and vane shear apparatus. Analyzing the role of the law and establishing the relationship between the strength of loess and thixotropy parameters model. The research results are as follows:(1) Loess strength increases with the increase of gypsum content, dry density and the curing time, decreases with the decreases of soluble salt content and water content. Strain increases of with the increase of gypsum content and dry density, and decreases with the increase of soluble salt content and water content. (2) Gypsum can effectively improve the effect of soluble salts on loess strength, while the presence of soluble salts weakens the effect of gypsum on the strength of loess samples. (3) Loess test of shear strength and thixotropy parameters increases with the increase of age, and increases with the increase of dry density and gypsum content, decreases with the increase of water content and the content of calcium chloride. The significant order of each factor is dry density, gypsum content, water content, soluble salt content.(4) The regression model between the parameters of the loess contact and the age, the content of gypsum, dry density and water content is established. The model is significantly higher, and the correlation between the parameters and the factors is good. The research results have important guiding significance for the design, construction and treatment of loess foundation.