LANDSLIDE BEHAVIOR INTERPRETATION BASED ON INCLINOMETER AND SURFACE DISPLACEMENTS MONITORING AT CUT & COVER 6, RAILWAY CORRIDOR VIII (N. MACEDONIA)

Summary

Abstract

A landslide affecting the Cut & Cover 6 (Tunnel 6) section of Railway Corridor VIII (Beljakovce–Kriva Palanka, North Macedonia) represents a critical geotechnical hazard due to the presence of highly weathered andesitic tuffs and a previously identified large fossil landslide. Although initial failures during excavation were local, construction activities posed a significant risk of reactivation, necessitating systematic monitoring of both subsurface and surface displacements. A comprehensive landslide monitoring program was implemented, combining inclinometer measurements and geodetic surveying of surface benchmarks. An inclinometer casing was installed in a strategically positioned borehole within the potential sliding zone, enabling long-term monitoring of subsurface deformations and identification of active shear horizons. Periodic inclinometer readings provided insight into displacement magnitude, depth, and temporal trends, supporting assessment of landslide activity state during excavation and stabilization works. In parallel, surface movements were monitored using precisely surveyed benchmarks, allowing detection of horizontal and vertical displacements of the slope and correlation with subsurface behavior. The integration of inclinometer data with geodetic measurements proved essential for distinguishing between local excavation-induced movements and potential reactivation of the larger fossil landslide. The monitoring results formed a key basis for design decisions, verification of slope stability analyses, and timely adaptation of temporary support measures. This case study highlights the importance of integrated landslide monitoring systems in complex geological settings, particularly for linear infrastructure projects where construction activities may alter pre-existing marginally stable conditions.