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-12- <br />~J <br />LABORATORY TESTING <br />The laboratory analysis included very careful detail logging of all <br />core obtained from the borings. Core was examined to determine locations <br />of fractures, orientation of bedding and relative competency of the rock. <br />Logs presenting the results of this detailed check are presented in Appendix <br />I. <br />The core was obtained using an NX wireline barrel. The sampling process <br />tends to wash and destroy the softer portions of the sedimentary rock. The <br />remaining intact core is indicative of the stronger portions of the forma- <br />tions. After most of the core had been examined and logged in detail, a <br />few samples were tested to confirm our visual estimates of relative strength <br />of the rock. In Boring No. 15 unconfined compressive strength tests were <br />performed at depths ranging from 42 to 422 feet. At 42 feet the unconfined <br />• compressive strength was 70,000+ psf for an undisturbed claystone sample. <br />The maximum observed unconfined compressive strength occurred in a sandy shale <br />sample from Boring 15C at 370 feet. The maximum strength tested was 685,000 <br />psf (4760 psi). The laboratory shear strengths tended to increase sharply <br />below 126 feet. These tests tend to support our opinions, based on examina- <br />tion of the core and correlations with the RQD. After examining the core <br />from the borings and reviewing the unconfined compressive strength tests <br />from Boring No. 15 it became apparent that the stability of the pit wall <br />would be controlled by the weaker, weathered claystones and sandstones which <br />occur to depths on the order of 100 feet. Sampling of these materials with <br />an NX barrel does not yield samples suitable for accurate shear tests. A <br />• <br />