PowerPoint Presentation

FACTOR OF SAFETYDetermining slope stability in Holtwood, PA in the aftermath of Hurricane Sandy

Kristina LofmanNovember 27, 2012EPS 109

S = Shear resistance (strength)T = Shear stress

Ca = apparent cohesion (kPa)f = unit weight of soil and field moisture (kN/m3)z = vertical soil depth (soil mantle thickness*cos) = slope angle (degrees) = internal angle of friction (degrees)u = pore water pressure at the failure surface (kPa)

At failure, S = T

Sidle, R. C., & Swanston, D. N. (May 01, 1982). Analysis of a small debris slide in coastal Alaska. Canadian Geotechnical Journal, 19, 2, 167-174. MECHANICS OF FAILURE FACTOR OF SAFETYPore water pressure is the only value that changes:

Increasing precipitation

Increasing pore water pressure

Decreasing shear resistance

To calculate FS for spatial data of slopes, run projectcode.Lofman.m using slope data (clip_output.txt)Black: minimal slope

Yellow: stable

Red (maroon):unstable