Experimental Investigation of Shear Strength of Carbonate Saline Soil under Freeze-Thaw Cycles

Abstract

Climate change is accelerating its adverse impact on ecosystems and infrastructure systems in cold regions. For extensive carbonate saline soil areas, their response to the freeze-thaw cycle remains uncertain. By considering the continuous intensification of freeze-thaw cycle frequency, the mechanical characteristics of carbonate saline soils are analyzed for different salt content (0.6% to 2.1%) based on the mechanical test in this paper. The purpose is to reveal the change law of shear strength and its parameters of carbonate saline soils under the scenario of continuous freezing and thawing cycles. The micro-characteristics of the carbonate saline soil before and after freeze-thaw cycling were analyzed by scanning electron microscopy, indicating changes in the structural soil properties caused by the combination of freeze-thawing and salinity. The scanning electron microscope images reveal the cumulative effect of frost heaving and salt expansion, i.e., increasing the number of pores between particles, reducing the effective contact between particles, and weakening the interaction force, resulting in cracks development. A series of mechanical tests demonstrate the stress-strain behavior of carbonate saline soils for different numbers of freeze-thaw cycles under different confining pressures. A transformation from strain-softening to strain-hardening is observed with an increase in the salt content from 0.6% to 2.1%. Furthermore, the shear strength of the carbonate saline soil decreases as the salt content and number of freeze-thaw cycles increase. The shear strength degradation mechanism is attributed to the cohesion and the internal friction angle. These shear strength parameters are critical in geotechnical analyses, such as evaluating of load capacity of foundations and slope stability in similar saline soils.

Effect of temperature on the dynamic parameters of silty clay in a seasonally frozen region

“…They found that the dynamic mechanical properties of frozen soils subjected to radial dynamic loading were closely related to the loading strain rate and temperature. Qiu et al 21 analyzed carbonate saline soils in cold regions using indoor tests and other methods, considering the effects of different numbers of freeze–thaw cycles and the salt content on the shear strength. The test results showed that the shear strength of the carbonate saline soils and the number of freeze–thaw cycles were inversely correlated with the salt content.…”