Seismic slope performance: Comparison of FEM results to displacement-based methods

Soil slopes from six types of generic soils (three sands and three clays) were modeled systematically as step-like slopes with the stress-deformation plane-strain finite element method (FEM). The models are assessed at different slope heights (5-20 m for the clay slopes and 5-40 m for the sand slopes), and monochromatic seismic loads with different frequencies (1, 2, 4, 6 Hz). At yield, the peak accelerations and slope displacements computed with the FEM are compared to the predictions from two displacement-based methods: Californian (Blake TF, Hollingsworth RA, Stewart JP (2002) Recommended procedures for implementation of DMG special publication 117: Guidelines for analyzing and mitigating landslide hazards in California. Southern California Earthquake Center, University of Southern California, California, 110p), and USGS Jibson (Eng Geol 91:209-18, 2007). For the slopes in clay, the results from the Californian method are in agreement with the FEM results for 4 and 6 Hz, while better matches between the FEM and the USGS method are obtained for 2, 4, and 6 Hz. The FEM results for the slopes in sand were compared to the Californian displacement-method only because this approach is calibrated with different types of materials and failure types while the USGS cannot be compared to these results as it is restricted to translational slip surfaces and the sands show more circular slip surfaces. The Californian predictions from the sand slopes are comparable, to the FEM results but with higher scatter. The FEM outputs provide further valuable insight among the relations from the different variables.