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- 37 - <br />(3) Development Rock Material: Determination of strength properties <br />of the development rock pile in a laboratory is not warranted for <br />a project of this size. Based on observation, the waste rock <br />appears to be a fairly well graded, angular to subangular <br />material ranging in size from approximately 12 inches to the U.S. <br />No. 200 sieve. Approximately 70% of the material is estimated to <br />be minus 1 1/2 inch. The angle of internal friction for several <br />types of rockfill materials have been previously studied by <br />Marsal. Marsal's results indicate that similar well graded <br />rockfill materials at low confining pressures had angles of <br />internal friction of between 42° and 48 °. A design strength <br />of 40° has been assumed for the stability analysis of the <br />development rock pile. <br />(4) Ground Water: No free ground water was measured to the maximum <br />depth excavated in the test pits at the time of exploration. <br />Leached Rock Drainability: Gradation analyses of the low -grade <br />uranium ore before and after the leaching process are shown in the <br />bottom graph of Fig. 15. The gradation analyses indicate that very <br />little change occurs in the particle size distribution during the <br />leaching process. The test results presented indicate that the final <br />3radation contained less material passing the U.S. No. 200 sieve than <br />the original ore. This is attributed to a loss in fines which <br />,curred in our laboratory during the handling of the material. A <br />nilar loss of fines will not occur during the actual process. <br />The results of the drainability tests conducted in our laboratory <br />assess the moisture content below which rapid gravity flow will not <br />occur are presented in the following table: <br />