Association Study on the Pore Structure and Mechanical Characteristics of Coarse-Grained Soil under Freeze–Thaw Cycles
Yao Liu, Hongwei Deng, Jingbo Xu, Guanglin Tian, Junren Deng
Abstract
In this study, the relationship between the pore structure and macroscopic mechanical characteristics of coarse-grained soils from mine dumps is explored under various freeze–thaw cycles. A series of experiments were conducted on the mine dump materials using a standard cube sample of 7 cm × 7 cm × 7 cm, a moisture content of 7.5%, and a density of 2.34 g/cm3. The pore structure test and uniaxial compressive strength test were carried out on the coarse-grained soil samples under different freeze–thaw cycles by using a nuclear magnetic resonance (NMR) instrument and a universal servo material testing machine. The study explores the change law of the strength and pore structure of coarse-grained soil, and establishes the correlation model between the pore structure and mechanical characteristics. The results showed that: (1) With the increase in the number of freeze–thaw cycles, the porosity of the coarse-grained soil gradually increased, and the bonding ability between the internal soil particles weakened, resulting in a decrease in strength. (2) With the increase in freeze–thaw cycles, the proportion of pore volume of the main peak and secondary peak 2 of T-2 spectrum curve increases gradually, and the internal pore structure of coarse-grained soil gradually develops towards medium and large pores. (3) There is an exponential function between the variation of pore volume proportion of each peak of coarse-grained soil and the relative strength value, and there is a good fitting coefficient between the two, indicating that the change of pore structure can well reflect the evolution law of strength.