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).
1 2 |
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) |
The assumptions of infinite slope analyses include (Coduto et al., 2011):
The slope face is planar and of infinite extent.
The failure surface is parallel to the slope face.
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.
See a geotechnical engineering textbook such as Coduto et al. (2011) for more background on slope stability theory.
James Kaklamanos <kaklamanosj@merrimack.edu> and Kyle Elmy <ElmyK@merrimack.edu>
Coduto, D.P., Yeung, M.R., and Kitch, W.A. (2011). Geotechnical Engineering: Principles and Practices, Second Edition. Pearson: Upper Saddle River, N.J.
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