REP33070

• Permit No: C1980007
• IBM Index Class Name: Report
• Doc Date: 10/29/1981
• Doc Name: Upper Waste Rock Pile - Prelim. Stability Evaluation
• From: Geo-Hydro Consulting
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

- 19 -
only.
Several important evaluations can, however, be made
from the stability analyses:
1. The upper bench and the slope below it appear to
to be stable when no ground water is present in
the area, even if we assume an unrealistically
low shearing resistance of the rocks and soils at
the site. It is therefore very probable that ground
water was a significant factor contributing to the
instability of the area and to the development of
the landslides.
2. The analyses show that factors of safety of the
slope could be close to unity when ground water is
present in one of the coal seams or in some other
permeable layer of the barren member.

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3. The analyses of the natural slope with no waste
pile above it show that the probability of shallow
failures, parallel with the surf ac e, is higher than
the probability of deep-seated failures. This con-
firms our interpretation of the mechanism of the
slides. Relatively shallow failures of the crests
of the benches are more probable in the area than
deep-seated, large landslides.
4. The analyses show a significant increase of factors
of safety if the slope is dewatered. If, for instance,
we assume a failure plane following the bottom of
the F seam and ground water existing within this
seam, dewatering of the area increases factors
e[aNroao coNw~m+c, wc.