Geotechnical Assessment of Roadbed Displacement and Pavement Distress on Mountain Roads in Southeastern Kazakhstan

Landslide activity represents a significant geotechnical hazard to mountain road infrastructure, particularly where roadbeds and pavement structures interact with unstable slope materials under complex geological and hydroclimatic conditions. This study assesses roadbed displacement and pavement distress at two mountain road sites in southeastern Kazakhstan: the Zharkent–Koktal-Arasan and Ayusai–Kosmostation highways. Field investigations included visual assessments of pavement and roadbed conditions, geodetic measurements of roadbed geometry and displacement, monitoring of pavement cracking, assessment of pavement technical and operational parameters, and characterization of geological materials. At the Zharkent–Koktal-Arasan site, the archived 2008 field dataset reported roadbed displacement of up to 4.5 m along the landslide-affected section. At the Ayusai–Kosmostation site, repeated surveys between 2021 and 2023 showed progressive development of transverse and longitudinal pavement cracking. Cumulative longitudinal-crack length increased at all monitored positions within the five test subsections, while the number of transverse cracks increased across all investigated crack-length classes. For one test subsection, an exploratory relationship between transverse-crack length and occurrence frequency was examined using three crack-length observations (R2 = 0.987); this relationship is interpreted only as a descriptive site-specific trend. The results indicate that road deterioration at the investigated mountain-road sections occurs within a multi-factor geotechnical environment involving slope-material movement, water-related processes, climatic effects, and pavement and operational conditions. The findings demonstrate that slope–road interactions can be manifested through contrasting infrastructure responses, ranging from progressive pavement distress to large-scale roadbed displacement, and highlight the need to integrate slope, drainage, roadbed, and pavement monitoring in the management of mountain roads exposed to unstable geological conditions.