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-T1- <br />• <br />The fire clay found below the coal in TP -6 was relatively soft and very <br />moist to wet. An intact sample suitable for direct shear testing was not <br />obtained. Direct shear tests were performed on a remolded sample of the clay <br />to evaluate the strength properties. Samples of the clay were prepared for <br />testing by placing the material into a 2.0 -inch diameter ring at the field <br />moisture content, compacted to about 100 pcf dry density. The results pre- <br />sented on Fig. A -6 indicate a peak angle of internal friction of 26.5 degrees <br />and a cohesion of about 400 psf. Residual values were lower with an angle of <br />internal friction of 24 degrees and a cohesion of 350 psf. It is our opinion, <br />that the values suggested by laboratory testing are riot representative of <br />the clay. Based upon previous testing we have conducted for the Eckman Park <br />Mines areas, we believe that the fire clay has cohesion less than 1,000 psf <br />• and an angle of internal friction less than 10 degrees. These values are <br />within the range suggested by the Canada Centre for Mineral and Energy Tech- <br />nology for materials similar to the fire clay. <br />EVALUATION OF HIGHWALL STABILITY <br />Portals for the underground mine will enter through the toe of a highwall <br />which parallels the existing pit wall. Present plans are to move the highwall <br />to the northwest. It is expected that the highwall would be moved no more than <br />150 feet and would have a maximum overall height of 80 feet. The direction or <br />strike of the cut will be the same as that which currently exists. <br />In our opinion, there are three basic rock types exposed in the highwall. <br />Bedding planes dip down into the cut which is beneficial for stability of the <br />cut. Major and minor joint orientations are relatively consistent. Most of <br />• <br />