Landslides - Causes, Types and Effects.pdf

In: Landslides: Causes, Types and Effects ISBN: 978-1-60741-258-8Editors: Ernest D. Werner et al., pp. 225-250 © 2010 Nova Science Publishers, Inc.Chapter 8PREDICTION OF THE SEISMIC DISPLACEMENTOF LANDSLIDESUSING A MULTI-BLOCK MODELConstantine A. StamatopoulosAthens, GreeceAbstractNewmark's sliding-block model is usually employed to predict the seismic displacement ofslopes. Yet, when displacement is large, the conventional sliding-block model predictsdisplacements that are larger than expected for the given input motion and soil strength.Alternatively, to simulate slope movement when the displacement is large, a multi-blocksliding model has been proposed. Similarly to the Sarma (1979) stability method, a generalmass sliding on a slip surface that consists of n linear segments is considered. In order for themass to move, interfaces where resisting forces are exerted must be formed between nodes ofthe slip surface. Thus, the mass is divided into n blocks sliding in n different inclinations. Forlandslides, the masses and lengths of each block entering the calculation are updated in termsof the distance moved. In addition, constitutive equations that simulate strength degradationalong the slip surface coupled with the multi-block model are proposed in order to simulatethe triggering of the slides. The chapter first describes the multi-block model and itsextensions for the prediction of the seismic displacement of landslides outlined above Then, itvalidates the above method by predicting the response of a well-documented earthquakeinducedlandslide.1. IntroductionNewmark's sliding-block model (Newmark, 1965), shown in Fig. 1, is usually employed topredict the seismic displacement of slopes (Kramer, 1996, Modaressi et al., 1995, Stark andContreras, 1998). Newmark's model consists of a block on an inclined plane. Criticalacceleration factor, k c-sl , is the minimum factor that when multiplied by the acceleration ofgravity, g, gives the horizontal acceleration which is just sufficient to cause movement of theblock. Every time during the earthquake that the applied horizontal acceleration is larger than