EOSC 114 Lecture Notes - Lecture 15: Shear Strength, Normal Force
27 Feb 2018
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Learning objectives: assess the balance between the strength of the slope and the destabilizing forces acing on it, compare and contrast landslide causes a. Steepest angle a slope can maintain without collapsing. As you tilt to a steeper angle: tangential force goes up, normal force goes down. Maximum angle before moving occurs: angle of repose. Driving force: component of gravity parallel to slope. Must be greater than driving force to stop slide. Maximum resistive force is called shear strength. Cohesion: higher in rock, lower in sediment. A little bit of water can be good. Shear strength: higher in rock, lower in sediment. Friction: moderate in rock, lower to moderate in sediment. We can model the stability of any slope by comparing resisting force to driving force. If driving forces are greater than resisting motion can occur. The factor of safety (fs): the ratio of shear strength to shear stress fs=tf/t. Slope starts to fail when factor of safety is 1.
