1997-07-28_GENERAL DOCUMENTS - M1973021 (9)

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' Highwall of the Central Quarry. The ma shows foliation jointing and other g Q rl' P J g ' joint set strike and dip data, dike and shear zone nature and location information, and other relevant geotechnical data on rock type and joint characteristics. ' B. Rock Core Borings Five rock core borings designated B 101 through B 105 were drilled as part of the slope stability evaluation and repair at the East Highwall of the Central Quarry. All of the borings were drilled by Golden Drilling, Inc. using a Dresser Industries skid-mounted, wireline, rock core drill rig. Double tube, ' split inner barrel, NX size diamond bit core barrels were utilized. The drilling was continuously monitored by a Haley &Aldrich field geologist who observed drilling conditions, photographed and stored the core, and prepared the field boring logs. Four of five core borings (B 101 - B 104) were drilled in locations to ' investigate subsurface conditions around and within the failure area to investigate the failure mechanism and design a repair. Boring B104 was an angle boring drilled at 40 degrees from vertical from above the slide head scarp intended to intercept the postulated failure surface high in the slide mass. A fifth boring (11105) was drilled well below the failure area from the quarry floor to investigate deeper subsurface conditions that may affect future ' slope development lower on the East Highwall. A location plan for the borings, and field logs and related summary information for data from the borings are attached as Appendix B. A figure showing the locations of the borings is included at the front of Appendix B. Another figure showing the locations of the four borings in the immediate ' slide area at a more detailed scale is also included at the front of Appendix D. The fifth boring falls outside the area shown on the more detailed boring location figure in Appendix D and was drilled in the southeast corner of the Central Quarry at approximately El 6490 (1996 floor elevation). A discussion of conditions revealed by the borings is provided below under "Geotechnical Data Analysis". C. Laboratory Testing Ten samples of rock core were selected and tested for unconfined ' compressive strength (ASTM D 2938). Results include wet density, failure load and unconfined compressive strength. One sample of a weathered clay gouge-filled joint was selected for a direct shear test(modified COE method). ' The resulting shear stress versus normal stress plot provided estimates of internal friction angle (0) and cohesion("C") for use in the slide repair design. In addition, five Atterberg Limits tests (ASTM D 4318) were ' performed on different clay shear/gouge samples encountered within the rock mass in the core borings. All laboratory testing was performed by Advanced ' 6 G:\PROIECCS\20200\002\96ANNRPT.WPD