Laserfiche WebLink
~1 <br />' C. PROPERTIES OF WASTE DUMP MATERIALS <br />' As mentioned previously, no samples of the waste dump material are avail- <br />' able for testing in our laboratory. It is anticipated, however,. that <br />blasted and excavated shales and sandstones from the Red Wing Mine will <br />produce fairly well-graded, angular to subangular particles in the gravel <br />r to cobble size ranges. Previous testing of the intact rocks indicate that <br />~ ' they have very high compressive and tensile strengths, thus indicating that <br />the broken particles will be sound, hard and durable, and should have a <br />' high value of internal friction due to interlocking. <br /> The angle of internal friction for several tyges of rockfill materials <br />" has been studied previously by Marsal.l The results of Marsal's tests <br /> on a similar, well-graded, angular shale rockfill are plotted on Figure III-4 <br />~ as angle of internal friction ($') versus confining pressure. Extrapolating <br /> the curves back to very low confining pressures, such as are applicable to <br /> infinite slope-type of stability analysis, shows that the angle of internal <br /> friction (¢') is between 42 and 48 degrees, whereas at higher confining <br /> pressures appropriate in the sliding wedge type of analysis, ¢' decreases <br />i to about 38 degrees at 150 psi. If a sliding wedge mechanism of failure <br /> were actually to develop in the waste dumps the soil would mobilize a ¢' of <br /> 3 to 4 degrees higher due to the influence of plane strain effects; thus <br /> 'might actually be 41 to 42 degrees. <br /> For the purposes of analysis and design, therefore, we have adopted a <br /> value of internal friction of ~' = 40°. <br /> <br /> <br /> <br />1Marsal, P.J., "Large Scale Testing of Rockfill Materials," JSM6FD, ASCE, <br />' Vol. 93, No. SM2, Proc. Paper 5128, March, 1967, Pg. 27-43. <br />W A WpRLER project 0823 III-3 <br />& RSSRCU(f6 <br /> <br /> <br />