Laserfiche WebLink
Morgenstern-Price's method was used as the search technique to determine the factor of <br /> safety of the open excavation cut in the stability analysis.This method is considered the most <br /> adequate because it satisfies all conditions of static equilibrium and provides a factor of <br /> safety based on both force and moment equilibrium. <br /> The existing conditions were modeled to obtain an estimated factor of safety for the Long- <br /> Term conditions. Shallow and deep circular failures were determined without groundwater. <br /> The cross section and material properties as described above were input into the software. <br /> A Morgenstern-Price analysis was completed for the existing site condition at Section A and <br /> proposed slopes for sections B through F. We understand that the proposed slopes will be <br /> constructed during mining and no steeper slopes will materialize during mining. Analysis <br /> results are presented in Table 2 below and figures for each analysis are attached. <br /> Table 2—Safety Factors <br /> Factor of Factor of <br /> Analysis SafetyAnalysis Safety <br /> Y <br /> Section A- Deep Failure 2.82 Section D - Deep Failure 4.56 <br /> Section A-Shallow Failure 2.42 Section D -Shallow Failure 1.80 <br /> Section B - Deep Failure 3.05 Section E - Deep Failure 3.50 <br /> Section B - Shallow Failure 1.54 Section E - Shallow Failure 2.27 <br /> Section C- Deep Failure 3.47 Section F - Deep Failure 3.06 <br /> Section C - Shallow Failure 1.71 Section F -Shallow Failure 2.35 <br /> 4. Conclusions <br /> The slope stability analysis shows factor of safety of over 1.5, which is a typical minimum <br /> factor of safety for this application. Surface water should be directed away from and around <br /> the excavation during and after construction. Surface water should not be introduced within <br /> the ground surface within 25-feet of the top of the slope. <br /> The highwall stability analysis (Section A) shows an adequate factor of safety. Backfill of the <br /> highwall is not necessary. <br /> Neighboring structures, utilities, parking lots, and roadways are unlikely to be impacted by <br /> slope failures when slopes are kept as proposed and groundwater is not introduced into the <br /> slopes. <br /> Water infiltration into the pit slope soils from surrounding development is not likely <br /> considering the topography and current state of development. <br /> Attachments: Stability Analysis Cross Sections C1.1—C1.4 <br /> Failure Surfaces and Safety Factors <br /> 20-8315-Native / Pierre Mine 12/10/2020 4:28 AM <br />