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~o <br />• Main CressonSlopeEvaluation AdrianBrown <br />Table 6. Shear Test Results <br />Hole Depth Material Cohesion Friction Comments <br /> feet psi deg <br />CC93-63 109 Tphd 0.0 45.0 <br />CC93-64 2S3 Tphd S.2 3S.S High peak <br />CC93-64 2S4 Tphk 0.8 38.7 <br />CC93-64 263 Tphk 2.S 39.0 <br />CC93-64 321 Tphk 0.2 37.5 <br />CC93-63 491 Tbx1L 6.3 42.3 <br />CC93-64 S61 Tbx1L 3.9 37.0 <br />CC93-64 628 Tbx1L 6.6 42.0 <br />Averages 3.2 39.6 <br />*'Tphd -Phonolite Dike; Tbx1L -Phonolite porphyry; TphK - Breccia <br />Source of data: Call and Nicholas; 1994, Appendix A, Table A3 <br />3.3.2 Field tests <br />• The observed performance of blocks and wedges of rock in the mine walls provides a means of <br />evaluating the actual frictional characteristics of mated rock surfaces at full scale. To evaluate this <br />performance, a survey of wedges and blocks located on, and missing from, the mine slopes was <br />conducted in 1995 by T.R. Brown of CC&V (Attachment 1). The survey identified approximately 200 <br />structures which formed wedges or planar blocks, and recorded whether the block or wedge remained in <br />position, or had been removed by sliding. The results of this survey are illustrated on Figure 1. <br />This study indicates that the effective angle of friction of blocks and wedges in the slope is <br />approximately 40°; below this angle of dip of potential sliding plane or intersection plunge most wedges <br />and blocks are stable; above it most are unstable. A few blocks and wedges remain on the wall on sliding <br />planes which aze steeper than 40°; these are probably indicative of some cementation, or unseen intact <br />rock on the apparent potential sliding plane. Conversely, some wedges and blocks are missing from the <br />wall with sliding planes which are flatter than 40°; these likely were removed from the face during <br />blasting, or during mechanical cleanup of the face which is a normal part of mining. <br />Figure 1 also indicates that the stability of blocks and wedges is not a strong function of direction of the <br />potential failure movement. The figure shows a relatively uniform distribution of failed and intact blocks <br />and wedges in all azimuth directions of the sliding plane. The data indicates that there may be a <br />preferential direction of lower friction angle (around 35°} for sliding planes with dip directions from 0° <br />to I80°, and a higher friction angle (around 4S°) for planes with dip directions from 180° to 360°. <br />However there is little difference in block or wedge stability as a function of orientation of the sliding <br />plane (nor by location). <br /> <br />1385D.980612 9 <br />