关键词: 粉砂质硫酸盐渍土, 冻融循环, 水盐迁移, 变形特性, 南疆地区

Abstract:

[Objective] This study aims to investigate the water-salt migration and deformation characteristics of desert saline soil in southern Xinjiang under the combined effects of water-salt replenishment conditions and salt-freeze-thaw cycles. [Methods] According to the types of saline soil and the distribution characteristics of groundwater and salt in the Aral region of southern Xinjiang Autonomous Prefecture, we selected silty sand as the research subject and prepared synthetic sulfate saline soil specimens to conduct cyclic salt-freeze-thaw experiments under two different salt replenishment conditions to simulate secondary soil salinization, namely, groundwater (saline solution) replenishment and engineering replacement (underlying saline soil) replenishment. The water-salt migration features, phase changes, and deformation characteristics of silty sulfate saline soil under the two conditions were analyzed. [Results] Under saline solution replenishment condition, as the concentration of the replenishment solution increased, the migration height of water and salt decreased. The soil deformation characteristics exhibited initial salt-induced swelling followed by settlement, with the maximum salt-induced swelling deformation of 0.21 mm occurring at a 5% solution concentration. Under saline soil replenishment condition, as the sodium sulfate content in the soil increased, the reduction in water and salt content in the lower layer increased, and the soil deformation was characterized by settlement. The maximum settlement deformation of -1.37 mm occurred at a saline soil content of 1%. [Conclusion] Compared to saline solution replenishment, saline soil replenishment results in greater thermal sensitivity of the soil. Under saline solution replenishment condition, the migration of water and salt in soil pores and the trends of deformation and failure occur more rapidly than those under saline soil replenishment condition. Therefore, replacing the sulfate saline soil foundation with an overlying layer of salt-free silty sand can suppress the sulfate-induced frost heave. However, the thickness of the salt-free silty sand layer should exceed the critical depth of thermal influence. In engineering practice, when silty sand—a soil type prone to settlement deformation—is used as an overlying replacement layer to suppress salt-induced frost heave deformation of sulfate saline soil, attention should be paid to particle gradation and compaction of replacement soil, and the implementation of salt-blocking and drainage measures. This research provides a reference for the engineering prevention and control of secondary soil salinization in southern Xinjiang.

Key words: silty sulfate soil, freeze-thaw cycle, water and salt migration, deformation characteristics, Southern Xinjiang