A 70m-high slope is currently under construction near the entrance of a cut-and-cover tunnel in the inner loop highway of City of Patras – a seismically active area in Western Greece (PGA = 0.24g). The slope consists of marl layers dipping inwards and exhibiting distinct sets of joints. The landscape provides evidence that the site has been subjected to a major landslide at an unknown time in the past. Geotechnical investigation detected a sheared zone at about 15m below ground surface, and a water table a few meters below the planned toe of the slope. The angle and position of the slope surface together with the estimated position of the sheared zone provide a chair-like potentially unstable volume with convex plan view. In addition to the general stability problem, surface instabilities due to the aforementioned sets of joints create the potential of smaller wedge-type failures near the surface of the slope. Following a detailed geotechnical investigation, nonlinear stress finite-element analyses considering both gravitational and earthquake loads were performed. The analyses encompassed a number of different assumptions about: (a) depth to water table, (b) soil strength and (c) geometry of slope and soil layer interfaces. Results show that adequate safety can be achieved using a combination of piles and passive anchors. The effects of various factors/assumptions on the safety of the slope are discussed
