Civil and Environmental Engineering 4426A/B Lecture Notes - Lecture 17: Centroid, Stability Conditions, Equipotential
15 Dec 2015
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Constant pore water pressure, u, along the failure surface. Seepage is parallel to the slope face. We are considering a very small element in an infinite slope, so we can assume that lateral forces are equal: r1=r2 , t1=t2. The unit weight of the soil, , below and above the water table does not change hp. Piezometric height at the base of the element: Pore water pressure at the base of the element: u cos w. 2 w u) tan bc b b tan bu tan bc. 2 bz h cos tan cos b. cos sin z h cos tan. Assuming c"=0 results in 26% reduction in factor of safety, which is a dramatic drop in. Considering that cohesion may not exist at all (most likely), the lower value of fs should be taken in design. This a good example of what a small value of cohesion does to slope stability calculations.
