Slope stability I EOSC316 Engineering Geoscience
Landslip trigger processes Water Toe removal –Natural –Artificial Head loading Vibration
Folkestone Warren, Kent Toe erosion due to extension of harbour wall, 1905 Since 1915 slide –mass concrete toe weights –drainage adits
Mt. Huascaran, Peru, 1970 earthquake triggered hit towns of Yungay and Ranrahirca, 18 km away, at around 150 km/hr Yungay completely buried, 66,000 dead
Types of landslide Rock failure –failure plane pre- determined Soil failure –failure plane along line of max stress
Rock failure
Planar translational slip in rock = angle of repose (= angle of friction) Factor of safety = shear force at failure / shear force
Wedge failure in rock
Toppling failure, Masada, Israel
Effect of cohesive strength on bench height in rock Shear stress on sliding plane: Failure occurs when: Thus Area of wedge
Half dome, YosemiteCarrara marble quarries, Italy
Rock failure – remedial measures
Slope failure in ‘unconsolidated’ material
Planar versus rotational slip in unconsolidated material Planar slip –frictional –cohesionless –C = 0 Rotational slip –frictional –cohesional –C ≠ 0
La Conchita, Santa Barbara, California, Spring 1995
Planar translational slip = angle of repose (= angle of friction) Factor of safety = shear force at failure / shear force
Planar slip - analysis
Planar slip in soils Cohesionless soils (φ=0) Soils with cohesion (φ≠0)