16th Symposium on Earthquake Engineering December 20-22, 2018 IIT Roorkee, India Paper No. 208
Seismic Stability of Slopes under Closely Spaced Buildings D. Raj1*, Y. Singh2 and A.M. Kaynia3,4 1
Research Scholar, Dept. of Earthquake Engineering, IIT Roorkee,
[email protected] Professor and Head, Department of Earthquake Engineering, IIT Roorkee,
[email protected] 3 Professor, Department of Structural Engineering, NTNU, Trondheim, Norway,
[email protected] 4 Technical Expert, Norwegian Geotechnical Institute, Oslo, Norway,
[email protected] 2
Abstract Rapid urbanization, infrastructure development and scarcity of flat land in hilly areas are often forcing people to involve in heavy constructions on hill slopes. Despite unfavorable conditions, densely located multi-storey reinforce concrete (RC) buildings are constructed on slopes to fulfill the commercial, residential and official demands. Further, the foundations of these buildings are mostly constructed at different levels in the influence zone of each other, due to limited space and restricted bay lengths. Some of the hilly areas are not only densely populated, but are also prone to seismic activities. Currently, existing standards/codes primarily focus on the design of buildings in flat regions, with only limited guidance for the design of buildings on hill slope. In addition, past studies on stability of slopes under building and seismic loads have mostly ignored the slope-building interaction. Form earlier studied, it was observed that the slope may fail either locally near the building foundation or globally including the buildingfoundation system. It was also observed that the position of the sliding surface, failure mechanism, and total and differential displacements are significantly affected by the type of shallow foundation (isolated and rigid raft), foundation distance from the crest of the slope and surcharge load on the foundation. The construction regulatory agencies, worldwide, are still struggling with the questions regarding the effect of height and density of buildings in such locations, and formulation of relevant guidelines. In this line, the behavior of homogeneous soil slopes under closely spaced adjacent buildings subjected to gravity and seismic loads is studied in this paper. Response of two representative slopes is investigated using nonlinear 2D Finite Element Limit Equilibrium Analysis based on strength reduction method. The seismic effect on slope mass and superstructure is considered using the pseudo-static method. The effect of interaction between building, foundation, and slope on the failure surface and factor of safety (FOS) is explored in detail. It is found that the buildings mostly result in local failure of stable slopes even under combined effect of gravity and seismic loads. Consequently, the slope's FOS is found to be sensitive to building height, but in most of the considered cases, it is insensitive to the number of adjacent buildings. Keywords: Seismic slope stability, Slope-building interaction, Strength reduction method, Closely spaced building, Factor of safety
