Abstract
In seasonally frozen areas, physical and mechanical soil properties change dynamically under the effect of the freeze-thaw cycles (FTCs), which is a problem that cannot be ignored in geotechnical engineering. In order to study the effect of the FTC on the strength and the mechanism of deformation and failure of saline soil, this paper took Nong’an saline soil as the research object. In total, 105 groups of remolded samples with different salt contents (S) after FTCs were examined in unconsolidated-undrained tests. On the basis of the experiment results, the influence of FTCs on the mechanical properties of Nong’an saline soil was analyzed. The failure principal stress difference (σ1 − σ3)f and cohesion (c) were both decreased with FTC. This occurred especially rapidly after the first cycle and became stable between 30 and 60 cycles. The internal friction angle φ increased at first and then decreased. According to experimental data, a modified Duncan-Chang model was established. Compared with the experiment results, this model was reasonable to simulate the stress-strain relationship of Nong’an saline soil. Furthermore, the empirical formulas of Duncan-Chang model parameters were obtained by regression analysis. This provides a theoretical basis for saline–soil foundation and subgrade engineering in seasonal frozen areas.
Highlights
In seasonal frozen–soil regions, the freeze-thaw cycle (FTC) is an important factor affecting soil’s physical and mechanical properties [1]
Because soil- structure changes caused by FTCs have a significant influence on soil properties, there are many previous studies on shear-strength changes of soils after FTCs [5,9,10,11]
Because the laws of stress-strain curve affected by FTCs were similar under different S, the stress-strain curve with 0.5% salt content is illustrated here
Summary
In seasonal frozen–soil regions, the freeze-thaw cycle (FTC) is an important factor affecting soil’s physical and mechanical properties [1]. Water in soil turns into ice, volume expansion increases pores, and the freezing process leads to aggregate separation and the breaking of soil particles. Changes in soil structure during the freezing process do not completely recover as the temperatures rises [2]. Under the effect of repeated FTCs, the soil structure is repeatedly adjusted, so its physical and mechanical properties are changed, such as porosity [3,4], severity [5], hydrologic properties [6], permeability [7,8], and strength and deformation [9]. The expansive soil remained stable after the first cycle, but soil volume increased, and c and φ decreased as
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