Slope Stability

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Description

These functions are used to determine the factor of safety against shear failure on slopes using infinite slope analyses (FSinf) or planar failure analyses (FSplanar).

Usage

1
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FSinf(c, phi, gamma, gammaW = NA, alpha, D, zw, metric)
FSplanar(c, phi, alpha, L, W, u)

Arguments

c

soil cohesion

phi

soil friction angle (degrees)

gamma

soil unit weight

gammaW

unit weight of water (default = 62.4 pcf for English units; 9.81 kN/m^3 for metric units)

alpha

slope angle (angle of failure plane) for infinite slope analysis; angle of failure plane for planar failure analysis (deg)

D

depth to failure plane

zw

distance of groundwater table above failure plane (use 0 for a dry slope and D for a submerged slope with parallel seepage)

metric

logical variable: TRUE (for metric units: kN/m^3) or FALSE (for English units: pcf) [this is needed if gammaW is unspecified]

L

length of failure plane (planar failure analysis)

W

weight of slope per unit width (planar failure analysis)

u

average pressure head on the failure plane (planar failure analysis)

Details

  • The assumptions of infinite slope analyses include (Coduto et al., 2011):

    1. The slope face is planar and of infinite extent.

    2. The failure surface is parallel to the slope face.

    3. Vertical columns of equal dimensions through the slope are identical.

  • For planar failure analysis, the angle of the failure plane is generally not equal to the failure angle. The geometry of the failure wedge is specified using its weight, W.

  • Either English or metric units can be used, but must be consistent.

Note

See a geotechnical engineering textbook such as Coduto et al. (2011) for more background on slope stability theory.

Author(s)

James Kaklamanos <kaklamanosj@merrimack.edu> and Kyle Elmy <ElmyK@merrimack.edu>

References

Coduto, D.P., Yeung, M.R., and Kitch, W.A. (2011). Geotechnical Engineering: Principles and Practices, Second Edition. Pearson: Upper Saddle River, N.J.