Assessment of Factors Contributing to Levees Stability

The paper focuses on the global instability of levees by analyzing those factors that contribute to the earthwork stability. Moreover, the effectiveness of naturalistic methods is reviewed. Global instability is caused by gravity and seepage forces. Therefore, different collapse mechanisms such as piping, overtopping, hydraulic heave, etc. are not considered. The levee geometry and its hydraulic and mechanical characteristics are the main factors controlling the stability. The material strength, in turn, strongly depends on the degree of saturation, and usually levees are partially saturated. Piezocone tests can be used for a quick evaluation of the effective stress state of partially saturated materials. On the other hand, geoelectric tomography can extend this information from given survey verticals to the whole longitudinal development of the considered levee. Partial saturation strongly contributes to the levee stability and therefore any technique aimed at maintaining the levee under this condition is extremely useful. Protection of the levee - sides by means of geogrids and bio-mats reduces the amount of infiltration water, helps the water adsorption by grass-vegetation and contributes to the mechanical strength thanks to the root-apparatus. The paper provides some preliminary results concerning the contribution of some types of grass to the material strength. The paper mainly shows a possible simplified approach that requires further developments and validation.