THE LANDSLIDE OF CORTES-DE-PALLAS, SPAIN

A large landslide in Cretaceous limestone and marl formations, reactivated by quarry excavations, has been stabilized by weight-transfer procedures designed by using a conventional limit-equilibrium analysis. The analysis was based on strength parameters derived from a back-analysis of the conditions leading to instability. Slide reactivation, excavation and filling have also been modelled by a finite element analysis in which the sliding surface has been represented by elastoplastic joint elements. This has provided important information regarding the sliding mechanisms and the effects of the remedial measures. Shear strength parameters determined in the laboratory are compared with those obtained from back-analysis. A significant discrepancy was reconciled when it was found that the sliding surface was located in a very thin and continuous clay layer of uncertain origin; possible mechanisms explaining the presence of the clay layer are suggested. The case demonstrated the importance of knowing in detail the geometry of the sliding surface, proves the value of field instrumentation and shows the fundamental role that geological details play in landslide problems.