A Review of the Research Status and Development Trends of the Physical and Mechanical Properties and Instability Mechanisms of Moraine

Abstract

This paper focuses on moraine deposits, a typical heterogeneous accumulation with wide gradation in high-altitude regions. The grain-size characteristics, structural features, damage evolution under freeze–thaw and water effects, and the research progress on slope instability are systematically reviewed. Particular attention is given to the application of methods such as sieving and image recognition, large-scale direct shear and triaxial tests, microstructural observation, and numerical simulation in revealing the mechanical behavior and failure mechanisms of moraine deposits. Based on existing studies, a unified framework of “material structure characteristics–strength degradation–slope response” is proposed to summarize the established understandings, remaining controversies, and engineering implications. The results indicate that moraine deposits generally exhibit wide gradation, poor sorting, strong structural characteristics, and pronounced water sensitivity. Freeze–thaw cycles, rainfall infiltration, and seismic disturbances jointly control the progressive instability process through particle rearrangement, pore expansion, fine particle migration, and interface weakening. Current studies still face several limitations, including difficulties in preserving in situ structure, significant scale effects in testing widely graded materials, and insufficient integration of multi-field coupling and multi-scale analysis. Future research should emphasize the characterization of intact moraine structure, experimental investigation of freeze–thaw–seepage–stress coupling, and the development of multi-scale numerical models, so as to support hazard prevention and control in high-altitude transportation corridors and major engineering projects in glacial regions.