SHALLOW LANDSLIDES IN DEEPLY WEATHERED SLATES OF THE SIERRA-DE-COLLCEROLA (CATALONIAN COASTAL RANGE, SPAIN)

Stability conditions in an area located NW of Barcelona (Spain) are di scussed. Here, several mass movements were observed, mainly affecting weathered Paleozoic slates. Many of these failures involved slopes cut along recent infrastructures: debris flows, wedge and plane failures, generally surficial, occurred more frequently. After a detailed geolo gical and geomorphologic survey, geomechanic characterization was carr ied out, according to RMR and SMR eeo classifications. This rating gav e a prediction of slope behaviour, in fairly good agreement with the r eal observed one. Stability numerical analysis was carried out for the main cut slopes, based upon the Limit Equilibrium Method. First of al l, the deterministic factor of safety was computed using the mean valu es of parameters. After that, a simulation technique based upon the Mo nte Carlo Method was applied in order to obtain factor of safety distr ibutions. The probability of failure was estimated as P(F<1). Finally, results from deterministic and probabilistic approaches were compared . The effectiveness of different possible remedial measures was highli ghted by means of a sensitivity analysis, which showed that the more i mportant parameters in the study area are the geometrical ones (height , slope and failure plane angles). The final technical solutions adopt ed are briefly outlined. (C) 1998 Elsevier Science B.V. All rights res erved.