PERMFILE133221 - Laserfiche WebLink

Home Browse Search

P, 03 Harding I.awsonlWest Elk Gob Pile Rock Testing Yage 4 of 4 • Shale bedding planes can be much weaker, however. The parted shale bedding at 78' appeazs to have little or no cohesion and a friction angle of about 17° in the range of 0 to 100 psi normal load, gradually changing to a whesion of 15-20 psi and a friction angle of 5-6° above 100 psi normal load. Tltis result would be highly dependent upon water content and drainage of the shal seam. Higher strengths in later portions of the higher normal stress runs reflect the wearing through to sandier layers at points of bedding irregularity. Mother silty shale seam at 64' disintegrated during the 100 psi normal load run, so its results are arguable. The silty shale does appear to be heading towazd a frictional strength in the neighborhood of 11° or so, however. e The most likely potential failure surfaces would therefore be formed by linear segments along discontinuitiesrather than circulaz or logspiral curves through intact rock (although the overall failure shape may be approximately circular or logspiral on a gross scale, depending upon the abundance and orientations of available structures). The steep backscarp section of a failure would probably have to be formed by an extensive joint or series ofjoints or fault in sandstone, while the underlying failure surface would Gkely be along bedding in a clayey shale seam or weathered shale seam. Such a failure surface could extend deeper than the hole that has been drilled if a weaker bedding plane exists below it. If worst case analyses using direct sheaz data show that failure is possible, additional strength data • plus field data on the actual orientations and locations of rock structures could be very important. Thanks for the opportunity to help you with this project. Sincerely, ROCKTECH William Klauber Principal • RGCKTECH 7494 Platinum Circk, War Jordan, UT 84GIS4 i.Yul )2ii-5222