Instability Phenomena in Municipal Waste Landfill. Numerical Modeling in Saturated and Unsaturated Conditions

Instability phenomena in waste landfills are not rare and the consequences are more severe than ones for typical landslide, having also environmental impact. Old waste dumps are often located in dried (or partially dried) valleys, natural gulches or ravines, therefore waste is often placed on sloped ground. Their mechanical characteristics are often very poor and, due to lack of drainage systems, are in saturated state. Therefore, instability can appear at every stage of the operation, during the closure or post-closing. The paper presents some aspects related to specific instability phenomena in waste landfills and dumps and to stability analysis in saturated and unsaturated state using numerical methods. As well, it presents a case study of an old dumpsite in Romania where a landslide occurred during the closing works and for which a consolidation solution was proposed, based on drainage and mechanical consolidation. Numerical modeling has been used for simulating the effect of the drainage and for evaluating the gain in stability, considering the unsaturated final state of the drained waste.