Effect of Salt Content on the Compressive Performance and Microstructure of Solidified Saline Soil

Salt crystallization causes a decrease in compressive performance and microstructral damage of lime cured sulfate soil. A series of tests, including unconfined compressive strength test, SEM observation, and EDS test, were conducted on lime stabilized soil with a salt content of 0.3% to 5% to study the relationships between salt content, compressive strength, and microstructure indicators. The results show that: (1) The compressive strength of the soil first increases and then decreases with the increase of salt content, and the strength of stabilized soil with salt content of 1.5% reaches its maximum. (2) When the salt content is less than 1.5%, the shape of soil particles tends to be an ellipse, and the soil structure becomes compact. After the salt content is more than 1.5%, the shape of soil particles tends to be a circle, leading to the instability of the soil structure. (3) For soil with low salt content, some salt particles fill the soil pores and play a role as soil skeleton, improving the strength of the soil. But the salt content is more than 1.5%, and salt swelling plays a dominant role, weakening the structural stability of the soil. Therefore, lime can be used to stabilize the soil with a salt content less than 1.5% to meet the requirements of oil and gas pipeline foundation engineering. Saline soil with a salt content above 1.5% cannot be directly used in engineering, and special research should be conducted.