1997-03-11_GENERAL DOCUMENTS - M1974004 (3)

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' intersecting discontinuities where sliding along the lines of intersection of the discontinuities can possibly occur. Sliding can occur because the plunge of these lines of intersection is less than the dip of the slope face. The stability of slope comes into question when the plunge of the lines of intersection exceed the angle of friction. This ' condition is represented by the intersection of great circles within the hatched region. If this condition exists and if the dip direction of either of the surfaces forming the intersection falls between the dip direction of the slope face, and the trend of the line of intersection, then sliding will occur on that plane rather than along the line of intersection. The following sections detail the findings of all field visits, and the results of stereonet analysis relative to each wall of the quarry. ' EAST WALL ' During the mapping phase of this project, the East Wall was mapped first, with progress ' then continuing counter-clockwise around the quarry. For simplicity, this convention will also be followed in this report. Photo 1 shows the entire East Wall. The foliations of the metamorphic gneissic bands can be readily seen in both Photo 1 and ' Photo 2. The largest structural feature in the quarry outcrops on the East Wall and can be clearly seen in Photo 3. A near east-west trending fault zone is 75-80 feet wide at the ' base and narrows to approximately 15 feet at the top of the wall. While the entire (75-80 feet) rock mass within the fault appears more fractured than the surrounding rock, most movement in this area has occurred along each edge of the fault zone, thereby bounding the fault with two clearly delineated shear zones. The steepness of the feature and its orientation, nearly perpendicular to the wall, eliminates this feature as a potential source of major instability for this wall. At no time throughout this investigation was there any indication of the presence of ' 12