Climate Change Effects on Transport Geotechnics: Mechanisms and Soil–Subgrade Performance Responses

Abstract

This paper presents a focused thematic synthesis of how climate change modifies the governing geotechnical mechanisms of transport support systems and how those mechanisms translate into soil and subgrade performance responses. The paper is derived from a broader PRISMA-screened review of climate-related geotechnical evidence for road and railway infrastructure. Within the parent evidence base, 291 records were initially identified, 244 non-duplicate records remained after database consolidation, 124 candidate studies were flagged during screening, and title normalization plus verification yielded 121 unique technical studies for thematic analysis. Rather than reporting a newly screened independent dataset, the present paper applies a secondary thematic regrouping to that parent corpus. Because coding was non-mutually exclusive, the synthesis is structured by thematic frequency rather than additive subgroup totals. In the regrouped evidence base, 59 studies addressed permafrost or frozen-ground processes and 69 studies addressed moisture, suction, or hydraulic response. The reviewed literature shows that climate-sensitive deterioration is controlled by coupled thermo-hydro-mechanical processes rather than by isolated variables. In cold-region settings, the dominant mechanisms are permafrost degradation, thaw settlement, frost heave, and hydrothermal restructuring, whereas in humid and seasonally wet environments the most recurrent controls are infiltration, saturation change, suction loss, and moisture-sensitive weakening. These processes alter stiffness, resilient modulus, deformation resistance, frozen-depth behaviour, and compressibility over time, indicating that subgrade performance under changing climate should be interpreted as an evolving system response rather than a fixed design property.