Strength and non-coaxiality behavior of warm frozen silt under inclined principal stress axes

Abstract

Under the background of global climate changing, the warming of permafrost has led to numerous engineering infrastructures being operated on warm permafrost foundations with diminishing bearing capacity. Meanwhile, infrastructure construction not only increases the overburden load on permafrost foundations but also induces directional deviation of the principal stress axis relative to the vertical direction. Therefore, conducting study on the stress-strain behavior and strength characteristics along different principal stress directions in warm frozen soils is imperative for accurately assessing deformation evolution patterns and bearing capacity of warm permafrost foundations. Thus, the stress-strain relationships respond, non-coaxiality evolution and strength distribution characteristics during directional loading along different principal stress directions were systematically investigated. The results indicated that the influence of principal stress direction on the strength intensifies with decreasing initial mean principal stress (when p_₀ = 500 kPa, the strength at α = 45° exhibits a 27.3 % reduction compared to the α = 0°). Concurrently, increasing initial mean principal stress diminishes both the stress-strain non-coaxiality angle and the directional dependence of strength. Furthermore, a novel strength model incorporating principal stress direction is proposed for warm frozen silt. These findings elucidate the correlation mechanisms between non-coaxiality evolution and strength anisotropy in warm frozen silt under fixed principal stress direction, providing theoretical foundations for optimizing engineering designs in permafrost regions under warming scenarios.