Stability Analysis of Silty-Sandy Earth Slopes Subjected to Earthquake Loading

Sahar Ismail, Riad Al Wardany, Fadi Hage Chehade

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Landslides and Geohazards

ABSTRACT: Geotechnical engineers have always considered slope stability analysis in evaluating land sliding risk, design of embankments and excavations, and in urban development of hilly areas. Under specific soil conditions and loading, soil slopes may undergo catastrophic failure and cause the destruction of properties and lives. This paper presents a comprehensive computer modeling study on the behavior of silty-sandy earth slopes under seismic loading using the finite difference method. The effects of the major factors that influence the behavior of soil slopes were investigated; these factors included: slope height and angle, soil cohesion, angle of internal friction and frequency of the seismic load. The influence of the model size on the results and that of boundary conditions were tested. The simulation results were presented in terms of the soil permanent displacement, the amplification of the soil particles velocity along the slope and the failure surface. RÉSUMÉ L'analyse de la stabilité des talus a été toujours prise en considération par les ingénieurs en géotechniques dans l'évaluation des risques de glissements de terrain, dans la conception des ouvrages en remblais et des excavations et dans le développement urbain des zones montagneuses. En effet, les pentes du sol peuvent subir une défaillance catastrophique sous certaines conditions du sol et de chargement, pouvant provoquer la destruction des propriétés et la perte des vies. Cette étude porte sur la modélisation compréhensive du comportement d'un talus limoneux -sableux sous chargement sismiques en utilisant la méthode des différences finis. Les effets des facteurs principaux qui influencent le comportement des pentes de sol ont été élucidés. Les paramètres testés sont les suivant : la taille du modèle, la hauteur et l'angle de la pente, la cohésion du sol, l'angle de frottement interne et la fréquence de la charge sismique. Les résultats des simulations ont été présentés en termes de déplacement permanent du sol, l'amplification de la vitesse des particules du sol le long de la pente et de la surface de rupture. 1 INTRODUCTION Slope stability of both natural and man-made slopes is a fundamental design/analysis problem in geotechnical engineering. The design of excavations, embankments and earth dams as well as the safety evaluation of natural slopes and land sliding against collapse is mainly conducted through static analysis of the slope. Dynamic analysis is used when the engineer needs to take into account the risk of slope instability when subjected to earthquake loading. Failed slopes in history were generally associated with extensive property damage and sometimes loss of human lives. In zones of high seismic activities, soil slopes become more prone to failure and the effect of earthquake on the design becomes the main constraint for the engineer. According to the Second Global Forum on Landslides which was held in Rome in 2011, damages that cost over 6 billion euros are caused every year by landslides in industrialized countries. For example, in 1999 Kocaeli's earthquake hits Izmit in Turkey, It was one of the few 7.4 magnitude earthquakes that have stroke a highly urbanized and industrialized region in the last fifty years. As a result, more than 17,000 people died and more than 120,000 housing units were either heavily collapsed or damaged leaving about 600,000 people homeless. In regions having low risk of earthquake, static conditions of loading apply to the soil slopes and the 'factor of safety (FOS)' against failure is generally used by the geotechnical engineers to assess the stability of their soil slopes. However, in zones of moderate to severe seismic risk, dynamic conditions of loading apply to the soil slope and a slope of good FOS in its static loading state may undergo catastrophic failure under seismic loading. Pseudo-static approach exists to evaluate the risk of failure of soil slopes subject to earthquake loading. This approach was found to be generally conservative. In fact, many slopes with low dynamic FOS calculated by the pseudo-static method, and which are predicted to fail under seismic loading did not really fail; they have rather shown certain permanent displacement on their surfaces. Thus, the need for more accurate methods of evaluation has pushed for the development of several higher methods such as the finite elements method, the finite difference method and other methods. These latest methods take into account the soil properties and the way

RÉSUMÉ: lity Analysis of Silty-Sandy Earth Slopes

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Sahar Ismail; Riad Al Wardany; Fadi Hage Chehade (2014) Stability Analysis of Silty-Sandy Earth Slopes Subjected to Earthquake Loading in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper398,author = Sahar Ismail; Riad Al Wardany; Fadi Hage Chehade,title = Stability Analysis of Silty-Sandy Earth Slopes Subjected to Earthquake Loading,year = 2014}