Abstract:

The hot-drying method for strengthening slope of foundation pit in loess holds potential application value, and the scientific evaluation of high-temperature loess crack evolution is a key link to verify the feasibility of the hot-dry method for strengthening loess. In this paper, a self-made experimental device was used to conduct crack evolution experiments on unsaturated loess samples with different initial dry densities and initial water contents at different high temperatures, and the changes in water content and surface crack of the soil samples were observed. Cracking indicators such as crack rate r, total crack length L, fractal dimension D, and average crack width W were quantitatively analyzed through experimental image processing. The analysis results show that r, L, and D all increase as the high temperature level increases, while W does not change significantly; the increase of initial dry density significantly reduces r, L, and D and significantly increases W; the increase of initial water content significantly increases r, L, D, and W. High temperatures significantly altered the crack initiation pattern of the soils, and the initiation cracks of the soils appeared rapidly under the 100 ℃ critical temperature. This may be related to the inhomogeneous extrusion of high-pressure water vapor. The high temperature greatly accelerated the fracture evolution process, but after exceeding 100 ℃, the acceleration of the fracture evolution was not significant. The mechanical mechanism of loess cracking and extension under high temperature is analyzed from the perspective of fracture mechanics, revealing the mechanism of high-temperature loess crack evolution. Considering the significant influence of matrix suction on crack evolution, a formula considering high temperature and matrix suction is established, highlighting the significant influence of high temperature on matrix suction to a certain extent.

Key words: loess, fracture evolution, high temperature, initial water content, initial dry density