REV13688 - Laserfiche WebLink

Home Browse Search

Memo to Steve Renner Fruits Highwall Stability page 5 Mr. Lewicki used Yang Huang's REAME computer program, which uses Bishop's method of slices for cylindrical .failure. Direct Shear Parameters: Fill Material: Angle of (Measured) Cohesion Density Fill Material: Angle of (Adjusted) Cohesion Density Internal Friction (B) = 36.8° (C) = 0 psf 116 pcf Internal Friction (B) = 41.0° (C) = 0 psf 116 pcf Results of Analysis: Portal Bench Fill Facial Slope Angle = 2h:ly (26.6°) Static Factor of Safety = 1.77 Sensitivity Analysis At 8 = 37' and C =.0 psf, FS = 1.54 At B = 34' and C = 50 psf, FS = 1.48 1992 Analysis (Highwall) During the fall of 1992 the Office of Surface Mining, Reclamation & Enforcement-(OSMRS) expressed a concern regarding the stability of the highwall at the Fruits mine. In response to the OSMREs concern, American Shield Coal Company was directed by the Division to analyze the stability highwall. Mr. Lewicki completed an analysis of the highwall which relied upon empirical evidence of the highwalls performance as evidenced in photography dating back to 1978. Mr. Lewicki demonstrated to the Division's satisfaction that the highwall had remained stable and intact from 1978 through 1992. The evidence demonstrated that only minor debris fall had occurred, as evidenced by limited blocks of rock on the reclaimed surface. Limited debris calving is characteristic of the surrounding natural terrain. The stability of rock faces is difficult to analyze. The intrinsic strength of the actual bedrock matrix, as tested in the shear apparatus, will normally withstand vertical slope angles. The stability of most highwalls, however, is controlled by the rock mass macro discontinuities, including faults, joints. and sedimentary bedding. Few models reflect these inhomogeneities with sufficient detail to accurately model the highwall mechanically.