Comparison on the compressive and tensile failure properties of frozen soil-rock mixture, ice-rock mixture and frozen soil

Understanding the mechanical properties of mixed frozen geotechnical materials, such as frozen soil-rock mixture, is fundamental to guarantee construction safety in cold regions. A series of uniaxial compression and Brazilian tensile tests were conducted to acquire the strength and deformation characteristics of artificial ice, ice-rock mixture, frozen soil, and frozen soil-rock mixture(FSRM). The mesostructured and crack patterns of ice-rock, soil-rock and soil-ice interfaces were also analyzed using a microscopic imaging technique. The result shows that: (1)Ice and frozen soil present comparative flat fracture surfaces while frozen soil-rock mixture and ice-rock mixture mainly present tortuous cracks. (2) Influenced by the shape of rock blocks(convex or concave/serrated boundary), there are two types of cracks in the ice-rock mixture: cracks along the accurate ice-rock interface or cracks inside the ice near the interface; cracks in FRSM mainly develop between the frozen soil and the soil-rock interface. (3) The compressive and tensile strengths have an increasing linear trend with decreasing freezing temperature. The strength increasing rate of FSRM and frozen soil is more sensitive than that of pure ice and ice-rock mixture. The ratio of compressive and tensile strength is about 5. (4) Under a temperature of-10 ℃, the compressive and tensile strength of samples are present in decreasing order as follows: ice_rock mixture>frozen soil>FSRM>ice. However, under a temperature of-30 ℃, frozen soil has the maximum compressive strength, followed by FSRM, ice-rock mixture, and ice, and the tensile strength is decreasing in the following order: FSRM>frozen soil>ice-rock mixture>ice. (5) In frozen soil-rock interface, ice could fill small pores or fractures of blocks, namely, having the interface interlocked. With a higher soil water content, soil particles from frozen soil could dissolve in water and form anice_soil mixed layer on one side of the soil layer at the ice-soil interface after freezing. Hence the strength of this layer is higher than that of pure ice, which effectively improves the strength of frozen soil. © 2021, Science Press. All right reserved.