Study on new method of freezing–thawing water replenishment and its mechanical properties for seasonally frozen soil

Abstract

The shear strength index of seasonally frozen soil is significantly affected by the freezing–thawing and water replenishment methods. To simulate the actual freeze–thaw and water replenishment process in seasonally frozen soil, a new method called the unidirectional freeze–thaw and natural water replenishment method was proposed. A test device was developed to facilitate this method. By using soil as the medium for water migration, the temperature change and water migration characteristics during the freeze–thaw process were investigated. The study also considered the influence of the samples' water content and the gradient between the water content of the test samples and the water replenishment soil layer. The changes in the soil stress–strain curve, static strength, and shear strength index under freeze–thaw were analyzed based on triaxial tests. The results revealed that the temperature change during the test process can be divided into six stages: rapid cooling, slow cooling, temperature stability, slow heating, continuous phase change around 0 ℃, and positive temperature stability. After freeze–thaw, the sample water content without gradient increased by approximately 0.6%, while the sample water content with a gradient increased by about 1.5%. However, the distribution characteristics of the water content were different. The static strength, cohesive force, and internal friction angles were all lower after freeze–thaw under different water content conditions. The maximum static strength and cohesion decreased by approximately 50% and 60%, respectively, under freeze–thaw, while the internal friction angle showed a slight decrease. The new freeze–thaw and natural water supplement method can serve as a basis for selecting the shear strength index of seasonally frozen soil.