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Ralston Quarry Slope Stability <br /> Remedial Measures In GROUND's opinion, in order to increase the factor of safety <br /> against failure in Zone 3, two stability embankments should be constructed along the <br /> slope across the full north to south width of the zone. The excavations to construct the <br /> embankments should be extended through the colluvium an into in-place shale (into firm <br /> weathered shale is sufficient) to interrupt the low-strength layer of colluvium underlying <br /> the tailings. This geometry is shown on the SlopeV P output below. The stability <br /> embankments are shown in green. Stability analyses of this geometry indicated a <br /> calculated Morgenstern-Price factor of safety against failure of about 1.3. <br /> Ralston Quarry <br /> Slope Stability Analysis <br /> 2a Section B-B Rernediated 1 30 <br /> 260 <br /> 2w <br /> 210 <br /> 200 <br /> y 180 <br /> 41 <br /> C, '60 Tailings <br /> Unt Weight=125 Pet <br /> 140 F-boe Angle=35' <br /> Cohesion=100 pst <br /> O 120 colluvium <br /> m Unit Weigtt=125 Pcf <br /> ¢ too Fnclion Angle=22' <br /> Cohesion=135 psf <br /> W <br /> claystone <br /> Unt Weight=130 pef <br /> F-1—Angle=20' <br /> X cohesion=1.000 psf <br /> 0 50 100 150 2W 260 300 350 400 450 Wo 550 600 <br /> Distance(feet) <br /> The stability embankments should be constructed of properly compacted granular <br /> material, similar to the tailings, exhibiting an angle of internal friction (4�) of at least 35 <br /> degrees and an effective cohesion (c) of at least 100 psf. <br /> Geotechnical parameters for embankment construction are provided in the Project <br /> Earthwork section of this report. <br /> Job No. 18-3046 GROUND Engineering Consultants, Inc. Page 17 <br />