Parametric Analysis of Weathering Effect on Possible Reactivation of the Valići Landslide, Croatia

Abstract

The Valici Landslide occurred near the Valici Lake in outback of the City of Rijeka, Croatia, in February 2014 after long term period of heavy rainfall. The landslide is located on the west slope in the middle part of the Rjecina River Valley which is an area susceptible to sliding with a lot of mass movements recorded in the past and recent history. Slopes in the valley are built of flysch rock mass while the limestone rock mass built the cliffs around the top of the valley. A flysch rock mass is highly susceptible to weathering which causes material disintegration, change of geotechnical properties and shear strength degradation resulting in instability processes in flysch slopes, unlike carbonate rocks with less susceptibility to weathering. In this paper the influence of weathering on flysch rock mass and a possible new long term rainy period on the reactivation of Valici Landslide is analyzed. Numerical analysis are made using LS-Rapid simulation software which integrates the landslide initiation process caused by pore pressure increase, motion process and finally deposition stage. To obtain input parameters for numerical model, undrained ring shear and direct shear tests on the samples of different weathering grades taken from the bottom of the Valici Lake were carried out. The results of numerical simulations demonstrate that raising of ground water level in the landslide body in combination with weathering of the flysch rock mass on the sliding surface will have the main influence on possible landslide reactivation and further landslide development.