ARCHIVED REPORTS_2004 - Laserfiche WebLink

Home Browse Search

STATIC AND SEISMIC STABILITY ANALYSIS Is WMU FU-04,FORWARD LANDFILL PROBLEM: Assess the static and seismic stability of the refuse over the base and side slope lining system for WMU FU-04 at the Forward,Inc. Landfill. GIVEN: These calculations have been previously performed for the prior WMUs at the site and they have been found to have a satisfactory factor of safety and seismic deformation. The analysis for WMU FU-04 is similar to WMU FU-03,WMU ART-03, and various other WMUs at the site. SUMMARY: 1. According to the site development and final grading plans for the site,the maximum planned elevation of refuse for the landfill is 170 ft MSL with 3:1 slopes and 20 ft wide benches every 50 vertical feet. The 170 ft elevation may only be achieved if waste placement occurs in adjacent waste management units. 2. The maximum elevation of refuse in WMU FU-04,prior to the development of adjacent waste management units, is 150 ft MSL.This elevation is based on 3:1 slopes on the south, east and west. The north slope is filled against an existing refuse slope. 3. Development is planned to the east of WMU FU-04. The east-facing slope of WMU FU-03 is therefore temporary. Waste placement in the adjacent cell to be constructed to the east of WMU FU- 04 will buttress the east facing WMU FU-04 slope. STABILITY ANALYSIS SECTIONS AND CRITERIA: 1. The critical cross section for the stability analysis is under the maximum filling configuration(refuse fill elevation 170 ft)in the N-S direction. 2. The acceptable static factor of safety is 1.5 for permanent slopes. For interim slopes, a static factor of safety of 1.2 to 1.3 is acceptable. 3. For seismic analyses, acceptable deformations are less than 1-foot. SUMMARY OF STABILITY ANALYSIS RESULTS I. The minimum factor of safety under the Forward Landfill maximum fill configuration(refuse elev. 170 ft)is 1.8. The critical failure surface extends from approximately the crest of refuse, through the refuse mass,and then along the base and slope liner. Both the base liner interfaces(clay/HDPE and cushion geotextile/HDPE)were analyzed but the clay/HDPE condition was found to be more critical. Failure surfaces extending along the base liner and through the interface liner slope were also searched but found to be less critical. From the seismic analysis, the anticipated amount of deformation is less than I-inch. 2. The minimum factor of safety under the central WMU FU-04 maximum fill configuration(refuse elev. 150 ft)is 1.7. The critical failure surface extends from approximately the crest of refuse,through the refuse mass, and then along the base liner. Both the base liner interfaces(clay/HDPE and cushion geotextile/HDPE)were analyzed but the clay/HDPE condition was found to be more critical.