Performance Based Design for Unstable Slopes in Highly Seismic Area

The design of slopes under seismic loading is typically undertaken by simplified pseudo-static methods. These approaches are usually conservative, as they fail to account for the real earthquake representation and the ground behaviour, therefore unnecessary costs for slope strengthening measures are introduced. Methods for assessing the seismic performance of geotechnical structures and soil-structure systems have evolved significantly in the last few years. This paper presents a case study of slope engineering design using a performance based approach in a highly seismic area affected by historic landslides. The approach is a deviation from routine slope design by aligning the performance of the slope with different deformation levels. The site response analyses, performed to select appropriate design acceleration values for the slopes, demonstrated that the presence of a shear zone within the landslide mass has a profound effect on the peak ground acceleration by acting as an isolator. The slope deformations were assessed using numerical and empirical methods. Substantial cost savings were achieved through the adoption of a performance based approach.