Study On Engineering Properties Based On Solidified Sulphate Saline Soil In Ningxia Area

Sulfate soil has the characteristics of dissolution,salt expansion and corrosion,and its composition is very different from the general soil.The solid phase contains crystalline salt,the salt solution in the liquid phase,and its strength and deformation characteristics are also different from the general soil.With the development of engineering construction,some engineering construction projects have to face the engineering hazards brought by saline soils in our country.Therefore,more and more experts and scholars began to pay more attention to the research of saline soils.They have made research on the mechanism,influencing factors and treatment methods of saline soil engineering diseases,and achieved certain results.This is of great practical significance and social value for the construction and development in salty soil areas and reducing unnecessary engineering hazards.In this study,the sulphate saline soil in Hongsipu area of Wuzhong City in Ningxia was used as the test material soil.After salt washing,the salinized soils were fixed and salinized.Under the control of the maximum dry density and the optimal water content,,Mixed with fly ash,calcium chloride and cement three kinds of curing agent,under certain conditions,the use of relevant laboratory soil teste on the curing characteristics of sulfate-saline soil of the research and analysis:(1)In order to improve the strength characteristics of sulfate saline soil,using fly ash,calcium chloride and cement three kinds of curing agent work together to modify sulphate saline soil.According to the orthogonal design requirements,mixed 0,10%,15%,20%fly ash,0,2%,4%,6%calcium chloride and 0,1%,3%,5%cement into the salt content of 5%sulfuric acid in saline soil respectively and measured the soil shear strength by triaxial test under conditions of freeze-thaw 1,3,6,9 times.(2)In order to decrease the salt expansion and collapsibility characteristics of sulfate saline soil,using fly ash,calcium chloride and cement three kinds of curing agent work together to modify sulphate saline soil.According to the orthogonal design requirements,mixed 10%,15%,20%fly ash,2%,4%,6%calcium chloride and 1%,3%,5%cement into the salt content of 5%sulfuric acid in saline soil respectively,measured the salt expansion capacity under conditions of temperature cascade decline from 35? to-25?C.In addition,using the uniaxial compression double-line method to measure the collapsibility coefficient.Through range and variance analysis,verified the influence mechanism of various factors on sulfate saline soil strength,expansion and collapsibility.The results showed that the ratio of three kinds of curing agents including fly ash,calcium chloride and cement has important influence on the engineering properties of soil:(1)Soil cohesion increases with the growth of fly ash and cement;with calcium chloride addition increasing,cohesion increases at first,then decreases;with cycles of freeze-thaw increasing,cohesion decreases at first,then increases.The internal friction angle does not change significantly,so it's less affected by curing agents and freeze-thaw cycles.(2)Soil expansion and collapsibility mainly in the initial phase of the test.Salt expansion ratio and collapsibility ratio decrease with the growth of fly ash and calcium chloride,but with cement addition increasing don't change significantly.Based on the comparative analysis of experimental data,it is suggested that 20%fly ash,4%calcium chloride and 3%cement should be used as the optimum curing proportion for the present study,which can provide effective reference for the foundation treatment of sulphate saline soil in the practical projects.