Influence of freeze–thaw cycles on mechanical properties of moraine soils

Abstract

The changes of mechanical properties of the soil caused by freeze–thaw cycles pose significant threats to the transportation systems that pass through the distribution area of moraine deposits. In order to study the mechanical mechanism and deformation characteristics of moraine soils, this study carried out a series of uniaxial compression tests, and the effects of different freeze–thaw cycles (0, 1, 3, 6 and 10), rock content (19.8 %, 41.9 %, 53.9 %) as well as water content (6 %, 9 %, 12 %, 15 %, 18 %) were considered. Besides, acoustic emission (AE) was utilized here to analyze the samples deformation response after the freeze–thaw cycle. Research results indicate that the stress–strain curves of the moraine soils exhibited four deformation stages. The AE counts of the samples were closely related to the rock content. After the freeze–thaw cycle, the AE signals of the samples with low rock content were more active in the compression stage and the linear elastic stage. However, there is no significant change in the AE counts of the samples with high rock content. Based on the fracture morphology, the failure modes of moraine soil could be divided into four types: oblique shear failure, splitting failure, bifurcation failure and bulging failure. After undergoing freeze–thaw cycles, the mechanical strength of the moraine soils is continuously reduced, and the reduction is fastest under the optimal water content for the uniaxial compressive strength (UCS). In addition, by orthogonal analysis, it was found that the most critical factors affecting the elastic modulus and UCS were water content and rock content, respectively. Studying the mechanical properties and failure mechanisms of moraine soils with different rock and water content after freeze–thaw cycles can guide the protection measures design for moraine soil slopes under different conditions.