Prediction analysis on limestone coastal cliff slope failures induced by undercutting of sea action, Al Khums area, North Western Libya

The coastal line of Al Khums area and its vicinity characterized by numerous cliffs made up by limestone rock masses with a face angle ranged from 82-87 degrees. These cliffs have been undergone consecutive planar failures induced by the undercutting of their toes by the sea waves action. Graded steel rods were used to measure the advance of undercutting during period of two years. The undercut was resulted to be varied between 0.32-0.57 m. The laboratory testing was performed on different lithologies encountered to determine the shear strength parameters as well as geometrical measurements were conducted to indicate the slope dimensions at the selected cliffs. The prediction analyses have conducted based on undercut advace per year, and the geometrical parameters of every cliff. However, this data has been used as a base to predict the new next cliff geometry and the mobilized friction angle and cohesive strength! and consequently the distance on the crest that would be lost per year. The environmental evaluation classifies this area to A, and B classes based on the rate of undercut and the predicted cliff loss. The remedy measures suggested to minimize the damage, are concrete rataining walls, wave breakers (Rip Rap), and occasionally rock bolts.