Kinematics of Slope Mass Failure at the Zone of Initiation, Guinsaugon Slide, St. Bernard, Southern Leyte

Gil G. Cardiel, MSc Eng’g Geology, PhD Geological Engineering (cand)
Engr. Gabino Belleza, MSc in Mining Engineering
Guillerma Jayne Atienza, MSc in Engineering Geomorphology Mark Llagas

Results of kinematic admissibility analysis and engineering geological zoning using Laubscher’s Rock Mass Rating Scheme and Hack’s Slope Stability Probability Classification Scheme indicate that the slope mass at the zone of initiation of the Guinsaugon landslide at St. Bernard, Southern Leyte failed by a combination of toppling, wedging and plane sliding. Among the various factors that contributed to slope failure are topography, lithology, structures, hydrogeology, and geomorphology. Field evidences also strongly suggest that various natural processes like weathering, gully erosion, previous slope failures and past earthquakes had significantly contributed to the geotechnical weakening of the slope mass prior to its failure. Among the identified triggering mechanisms are intense rains of long duration (i.e. 478 to 571.2 mm which is four times more than the average rainfall reading at Southern Leyte) coupled with the occurrence of low magnitude earthquake.