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~tambcrt ai1D R,s,sociatc,.~ <br />_ CONSULTING GEOTECRNICAL ENGINEERS AND MATERIAL TESTING <br />• August 5, 1993 <br />Mr. Don May, P.E. <br />735 East 7th Ave. <br />Durango, CO 81301 <br />Subject: National King Coal Direct Shear Test results <br />Mr. May, <br />APPEND. 7 (3 <br />Thie letter presents the results of our direct shear test of <br />the formational material sampled from cur test borings lec~ted <br />northeast of the National King Coal mine maintenance and shuttle <br />storage building. The test boring was advanced on July 21, 1993 <br />at the south end of the upper surface of the coal gab pile. We <br />advanced the boring through the gob and obtained drive type <br />sleeve samples of the formational material at the elevations you <br />requested. <br />We analyzed the direct shear test data at an elongation of <br />. 0.050 inch (approximately 2.5% strain) and obtained an angle of <br />internal friction of 45 degrees and a cohesion of about 0.5 pound <br />per square inch (approximately 72 pounds per square foot). <br />Due to the variable and laminated nature of the observed <br />formational outcrop near the test boring we anticipate that the <br />physical strength characteristics vary within the unit. We <br />anticipate that the claystone portions of the material generally <br />will have a lower angle of internal friction and higher cohesion, <br />while the sandstone portions will have higher angle of internal <br />friction and a lower cohesion. The sample we tested consisted of <br />a very fine grained well sorted lithic sandstone. <br />If you have any questions, please contact us. <br />Respectfully sub , <br />LAMB ANI~ CIATES <br />~~ <br />e~ ~Tr ner P E. <br />r go Of ice Manager <br />cc: Tom Bird <br />P O BO%3986 <br />GRF':D JUN;TiON. CO 81502 <br />(3T i 245~65Jf <br />PO BO%OOaS <br />MONTROSE. CO 6teC2 <br />(303; 2a9~2 t 5: <br />aE3 TURNER, t0a 4 <br />DUFF.'.G ~. CO 61301 <br />(3 i3~ 259~57y5 <br />r>a>> issa <br />