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329 <br />SLOPE STABILITY <br />• The slopes analyzed at the mine site were at Station 49+25 and 51+00, shown on Fgures <br />3.1.4 and 3.1.7. Cross sections of these areas are shown on Fgure 3.1-9. The soil in the area <br />of the mine site is the same as the colluvial soil found along the upper portions of the mine road. <br />This soil is a highly cohesive clay, 1,300 PSF; with a relatively low angle of internal friction, 15° ; <br />and a density of 130 Ib/ft3. <br />The first line analyzed is along the top of the ridge that will be created when the slope is <br />reclaimed, Station 49+25. The analysis of the first line indicated that the existing configuration <br />has a stability factor of 1.346. Analysis indicates that the stability will be improved to 1.439 <br />upon reclamation. <br />The second area analyzed is located approximately half way between the first line and the <br />existing roadway portal near the sediment trap. This area was chosen for analysis since it is the <br />area where a slide developed when water draining from the road which existed prior to mining <br />above the slope saturated the slope and caused a slide in the area. The slope has been stable <br />since the water running down the road was directed back into the natural drainage with a water <br />• bar. This will also be the tallest reclaimed slope after the area has been recontoured. Coal from <br />the Loma Loadout will also be used to backfil{ near the existing portals as is shown on Fgures <br />3.1.4 and 3.1.7. In consultation with the Division, the coal strength parameters were defined as <br />a cohesion of 0, an angle of friction of 15° and a density of 100 Ib/ft3. GVC will submit a <br />textural analysis of the coal to be backfilled to the Division by January 31, 1997 to show that <br />the coal does not contain excessive fines that would require revision of the strength parameters. <br />Stabilityy analysis indicates the curcent factor of safety is 1.20; which is marginally stable, and <br />definitely susceptible to slope failure with the increased water content that was experienced <br />prior to putting the water bar on the road above the slope. Stability of the reclaimed slope was <br />considered for two cases. The first does not include the use of coal to backfill the slope while <br />the second does. Analysis indicated that the failure circles of the two cases have origins in two <br />different locations; therefore, both centers are analyzed in each case. The first case yields a <br />safety factor 1.503 and the second yields a safety factor of 1.358. h will be important to <br />ensure that the watert>ar not effected by the reclamation of the area to ensure that the slope <br />. does not get saturated again. fF the waterbar is effected during reclamation, it will be repaired <br />or replaced as necessary. <br />A4U Volume I 12 - 18 - 96 <br />