Collapse and Remediation of Vrhole Landslide

The first signs of instability of a 20 m high cut, which was executed during the construction of Ljubljana-Maribor motorway in the nighties, were observed in 2010. On the bottom of the cut, next to the shoulder of the motorway, there was distinguished ground heaving while some 2 m deep cracks appeared on the body of the sliding mass. Approximately 100 m wide landslide was formed endangering the traffic on the motorway. A comprehensive site investigation was carried out in 2011, which included measurement of movements and the installation of the set of piezometers and inclinometers. Based on the contemporaneous state of the landslide and the results of site investigation the design of the remediation was carried out. The design, which comprised a 100 m long pile wall and deep drainage, was never applied in practice. During the night in the spring in 2013 the landslide collapsed and the debris covered all three lanes of the motorway in Ljubljana direction. Fortunately, the maintenance services were quickly informed and the motorway was immediately closed so that there was no material or human loss resulting from the landslide. The new design of the remedial measures, which conformed to the newly developed boundary conditions, was carried out in 2014. The new design comprised deep drainage and the gravity wall, so that the landslide was fully stabilized during the same year. Geological conditions, the ground model, causes of instability and remedial measures are presented in the paper.