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' V. GEOTECHNICAL ANALYSIS <br /> ' 5.1 General <br /> Specific slope stability analyses were not conducted nor required for mining activities <br /> ' performed during 1997. Rather, observed conditions were compared with assumed <br /> conditions used as the basis for design and consistent with the Observational Method <br /> discussed previously herein. <br /> ' Two rock mass conditions were previously analyzed during design, and used as the <br /> baseline for further evaluations: "Competent rock", representing the majority of expected <br /> ' conditions, and "poor rock" representing localized areas of shearing, weathering or <br /> adverse jointing, were the two baseline conditions. Typical in-situ rock mass <br /> characteristics for each of these baseline conditions and the corresponding strength <br /> ' envelopes and calculated safety factors were presented in Permit Amendment No. 3, <br /> Section 4-04. <br /> ' Following are descriptions of general ground conditions observed relative to the baseline conditions for each of the areas worked during 1997. <br /> ' 5.2 East Highwall of the Central Quarry <br /> A. General <br /> ■ The highwalls and benches are aligned at approximately N25°W to <br /> N30°W, except at the south end of the highwall where they are being <br /> developed at approximately N 10°W. <br /> ■ All rock excavated was at deeper levels below the shallow weathered <br /> zone and is estimated to have an unconfined compressive strength of at <br /> ' least 15,000 psi although localized zones of weaker rock are present. <br /> ■ The primary joint set along foliation of the gneiss rock has been <br /> observed to date to generally strike sub-parallel with the slope and dip <br /> 20 to 60 degrees in a westerly direction, sub-perpendicular to the slope. <br /> Observations in the 5th and 6th highwalls made for 1997 show.a change <br /> ' in trend. The historic pattern persists at the north end of 5th highwall, <br /> but varies to striking more sub-perpendicular to the slope along the <br /> southern parts of the 5th and 6th highwalls which is a more favorable <br /> orientation for slope and highwall stability. Foliation dip there varies <br /> from approximately 15 to 50 degrees, generally to the south, but locally <br /> to the north due to folding. Dip components both into and out of the <br /> ' slope are common. <br /> ■ Spacing of joints in the primary joint set typically ranges from several <br /> inches to approximately three ft. Joint surfaces vary greatly from fresh <br /> ' to highly-weathered, clay-filled, and/or slickensided. Weathered schist <br /> ' 8 G:\PROJEC-rS\-10200\002\97ANNRfr.WPF <br />