Major Parameters that Affect Outcome Landfill Slope Stability Modeling, ISWA, September 2105, J. Law

landfill slope stability
James Law of SCS Engineers presented this paper at the 2015 ISWA conference in September.

This paper presents the sensitivity evaluation of two major parameters used in a landfill waste slope stability during landfill operations and final slope configurations. These key factors are:

  • Weakest interface shear strength of the bottom liner system.
  • Presence of leachate head above the bottom liner system.

The results of this evaluation illustrate the importance of knowing how much leachate head is allowed on the bottom liner system. It is possible to determine how much textured geomembrane is needed (for those landfills that used exclusively smooth geomembrane) to maintain a targeted factor of safety against slope instability and the maximum amount of leachate head on liner allowed without triggering instability of the landfill.
The methodology presented herein can be used for evaluating if the landfill operating or final slopes are likely to maintain a slope stability’s factor of safety above 1.5, under certain leachate levels that are either measured in the field or by observation of sideslope seep locations. Site-specific slope stability modeling, taking into account actual slopes, material properties, liquid levels and other factors should always be performed for any landfill sites during the design phase.

by H. James Law, P.E., BCEE, LEED AP BD+C