PERMFILE67948

• Permit No: C1980001
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: PROCEDURE FOR CALCULATING FACTOR OF SAFETY FOR ROADWAY CUTFILL SLOPES
• Section_Exhibit Name: 3.5 APPENDIX 3.5-B
• Media Type: D
• Archive: No

ROAD FILL EMBANKMENT SLOPES
Road fills at the Edna Mine are constructed of The best available material that
can be easily and economically obtained. Spoil material consisting of broken sandstone,
shale and clay is commonly used. Because of the angular shapes and varying groin
sizes, this material interlocks together to form a tightly packed and stable fill. A
representative "worst case" slope was selected for a slope stability analysis. The road
fill slope was found to have a slope angle of 32°. Other properties of the moteriat
relevant to slope stability is unit weight, cohesion and friction angle. :The unit weight
of the compacted fill material was estimated to be ISO Ib/ft3 with a cohesion of 7500
Ib/ft2. The friction angle was defined.os the angle of repose of the material of 37°.
Since the angle of the slope is less than the angle of repose, the slope would fail only
if outside forces acted on it. These forces could include woter pressure or additional
weight on the fill. Since road fills at the Edna Mine are well drained at both the top
and .bottom of the embankment, water pressure was assumed to be negligible.
However, the weight of a loaded haul truck applying a vertical force to the fill was
considered.
• Factor of Safety Calculation fora Representative Road Fill Slope
Slope Angle - ~ = 32.2°
Friction Angle - ~ 37° (Angle of Repose)
Unit Weight - Y = 150 Ib/ft3 (Compacted Material)
Cohesion - c = 7500 Ib/ft2 (Compacted Material)
Water Uplift Pressure - Q = 0
Truck Weight - T =41625 Ib/ft2 (Slice /f5 Only)

Slice
(ll) Unit
Weight
(Y) Height
of Slice
(H) Vertical
Stress
(YH) Width
of Slice
(fix) Angle
of Slice
(a)
I ISO 7 1050 IS 0.2°
2 150 14 2100 IS 11.3°
3 150 20 3000 15 19.7°
4 150 22 3300 15 33.7°
5 150 10 1500 15 46.4°
•
Revised 3/82 3.58-14