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<br />strikes N40°E with variations of up to 90 degrees in both directions and dips 20 to 60 <br />degrees south. Overall, this orientation strikes approximately parallel with the slope <br />and dips into the slope, but with significant variations to the west and east. Joint <br />spacings typically range from several inches to approximately five ft. Joint surfaces <br />vary greatly from fresh to highly-weathered. Weathered schist interbeds having a <br />slick and weak character are frequent throughout the rock mass. <br />At least two secondary joint sets are present, generally orthogonal to the primary joint <br />set although, in some cases, they cut through and are independent of the primary <br />jointing. These secondary joints typically occur at intervals of one to five ft. In <br />general, secondary joint surfaces are fresher and less-weathered than the primary <br />joints along foliation and do not typically exhibit the stnoo[h schist or mica surfaces. <br />Based on the conditions observed with the present exposures, the rock mass at the south <br />end of the Central Quarry is tentatively classified as "poor" in terms of the previously- <br />established baseline conditions. The term rock mass incorporates the parent rock material <br />plus jointing and other characteristics which influence behavior of the mass. This classifi- <br />cation is based primarily on the low strength of the parent rock material, but also on the <br />three joint sets and the low shear strength of some of the joints due to the smooth surfaces <br />and weathering. This classification may change as additional rock is exposed in this area. <br />In general, [he joint orientations are neither advantageous nor detrimental to slope stabil- <br />ity. Although the primary jointing is often advantageous, significant variations exist and <br />secondary jointing is often disadvantageous. Localized areas of instability were observed <br />and will continued to be a concern during further development in this area. <br />Based on these observed conditions and on comparisons with baseline conditions for <br />previous analyses, slopes at the south end of the Centra! Quarry are presently being <br />excavated at an overall inclination of approximately ]H:1V or flatter. <br />East Highwall of the Central Quarry. Results of the geologic mapping at [Ire East <br />Highwall of the Central Quarry revealed the following general conditions: <br />The highwafls and benches are aligned a[ approximately N30°W to N40°W. <br />2. The parent rock material within the weathered zone is weak and is estimated to have <br />an unconfined strength less than 15,000 psi. The weathered zone exists at the ground <br />surface and extends to a depth of 10 to 50 ft, depending on location and also in some <br />zones below that depth. <br />3. The parent rock material below the weathered zone is typically strong and is <br />estimated to have an unconfined strength of at leas[ 15,000 psi although zones of <br />weaker rock are present. <br />4. The primary joint set is along foliation of the gneiss and schist rock and strikes <br />approximately N60°W to N10°E which is sub-parallel with the slope, and dips 40 to <br />60 degrees west which is approximately perpendicular to the slope. Approximately <br />70 percent of the joint set measurements fall within the stated range. Folding and <br />shearing has created a series of small synclines and anticlines from approximately 50 <br />4 c:~ozao~ROwao.zao <br />