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<br /> <br /> <br />1 <br />1 <br /> <br /> <br />i <br /> <br /> <br />1 <br /> <br />1 <br /> <br /> <br /> <br />1 <br /> <br />1 <br />Table 1. Dominant Joint Sets Along the East Side of the Central Quarry <br />Joint Se[ Strike Dip and Dip Direction Significance <br />Primary N70W N22W 25SW 52SW High <br />(w/foliation) N25E N49E 27NW 48NW Low <br /> N80W N66W 34SW 70SW High <br /> N30E N41E 30NW 35NW tow <br /> N90W N48W 36SW SOSW Low <br />Secondary N69W N15W 74SW 78NE Low <br /> NODE NISE 74SE 90 Low <br />Two dominant secondary joint sets are present. These joint sets are orthogonal to each other, <br />with strike orientation of one in a northwest direction, the other in a northern direction. <br />These joints dip steeply to near vertical into and out of the mining face. The secondary joint <br />sets are shown in Table ] . Spacing of joints in the secondary joint set typically range from 1 <br />to 5 feet. Joint surfaces are typically tight and appear fresh to slightly weathered. Joints are <br />both continuous and discontinuous. These joints cause the final highwalls to be relatively <br />smooth and vertical. <br />Slope failures are limited to infrequent and relatively small block and wedge failures, <br />generally less than 10 feet in length. These types of failures are as expected for the highwall <br />and only cause localized opera[ionalinconveniences. <br />Three major fractures were identified in the southern end of the east side (Plate 1, Locations <br />K, R, and U), These fractures are very continuous and are orientated sub-perpendicular [o <br />the slope and dipping out of the slope. These fractures do not occur along foliation planes <br />and are visible from 30 to 100 ft in length along the highwall. <br />The condition of the overall slope in the vicinity of Benches A and B is between "competent" <br />and "poor." This is an improvement over the rock mass high in the slope which is "poor." <br />There are localized areas of instability on individual benches. These typically occur where <br />the primary joint set (foliation) strikes parallel with the slope, and where anticline syncline <br />axes daylight in bench highwalls. These localized instabilities are typically slabs and wedges <br />sliding on the primary joint set (foliation) that is freed with a secondary joint. Mapping of <br />the highwalls revealed that the primary joints (foliation) is not continuous and changes from <br />one bench to the next, and every 20 to 100 ft along each bench. Additionally the weathering <br />of [he primary joints is described as fresh to moderate. This is in contrast to the larger <br />instability near ttte top of the east highwall in which the slide surface was a highly weathered <br />and clay filled, and extended over several benches. <br />In general the competency of the rock mass at the lower benches is better than at the upper <br />benches. This is the result of a lesser degree of weathering, especially along the primary <br />joints, and the presence of the iron-rich rock. The iron-rich rock has a jointing pattern <br />different from the gneiss, and tends to break up the unfavorable jointing in the gneiss. Based <br />on the rock mass conditions observed, the condition of the rock mass of the new tlnal <br />highwalls developed during 1999 has significantly improved compared with the conditions <br />used as the baseline tier analyses of the east side. <br />G.~FNO1 H"r5¢0?W Alnrrison Iluarp~V%16\1~Y19\rrewppmarWp.tloc <br />