Infinite Slope Stability with Seepage
Why a slope that stood dry all summer slides in the spring: with steady seepage parallel to the slope and the water table at the surface, FS = (c' + (gamma_sat - 62.4) H cos^2 beta tan phi') / (gamma_sat H sin beta cos beta). The pore pressure cuts the friction term to the buoyant weight while the driving weight stays saturated, so a cohesionless factor of safety drops to (gamma_sat - 62.4)/gamma_sat -- about half. A phi = 32 sand at 18 degrees is a safe 1.92 dry but a failing 0.96 wet; the tile shows both so a subdrain's value is obvious. Translational, drained, no seismic. A screening aid, not a stability analysis.
Formula and source
driving = gamma_sat H sin(beta) cos(beta); resisting = c' + (gamma_sat - 62.4) H cos^2(beta) tan(phi'); FS = resisting / driving. (c' = 0 gives FS = ((gamma_sat - 62.4)/gamma_sat) tan(phi')/tan(beta))
The infinite-slope stability model with steady slope-parallel seepage on an effective-stress basis, as compiled in Das (Principles of Geotechnical Engineering) and the NAVFAC DM-7 slope-stability references, by name.
Audience
This tile is built for trades and the adjacent professions in the Carpentry and Construction group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.