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1 <br />1 <br />1 ~ ROCKY MOUNTAIN GEOTECHNICAL, INC. <br />' Achieving Harmony with Earth AUCJUSt 31, 1981 <br />Ute Engineering & Surveying Co. <br />' Box 674 <br />Delta, CO 81416 <br />' Re: T,ddendum to Slope Stability Analysis <br />Refuse Disposal Area <br />Red Canyon Mire <br />' Attn: LeRoy Black <br />Dear P7r. Black: <br />^ As we indicated at the time our original reF•ort was submitted, the <br />graphical presentation of shear strength data for the Red Canyon <br />' Mine coarse coal refuse material was not available. This letter <br />will provide detailed information pertaining to the coarse coal <br />refuse and other soil materials, as well as the sample data and <br />' graphical representation of shear strength for the refuse. General <br />information on soil index properties and classification will be <br />found on the Soil Summary Sheets accompanying this letter. Pertinent <br />' data with respect to the: triaxial shear strength tests is as follows: <br />The material was found to have an effective st ss friction <br />angle of 28.5 degrees, and a cohesion inters= of 1.4 psi, <br />' or 200 psf. The sample was placed at an initiui wet density <br />of 94,9 pcf. The initial water content was determined to be <br />20.7$. The initial dry density was 78.7 pcf. Due to the corn- <br />' pcsition of the material, however, some volatile hydrocarbons <br />may have evolved in drying. Therefore, the true water content <br />may be slightly less ~han that value. Strain rate use~3 during <br />' testing was 2.9 x 10 cm/min. The type of test was a multi- <br />phase staged, triaxial shear strength test performed as consoli- <br />dated, undrained with pore pressure measurements. Average fail- <br />' ure strains were i.2$. Overall volume consolidation was 4.5$ <br />Shear strength parameters were determined from a stress path <br />plot showing values of of= 25.5 degrees, and a = 1.25 psi. <br />Stress path plots plus plots of A factor, excess pore pressure, <br />and deviator stress vs. strain will be found accompanying this <br />letter. <br />' Should you have any additional question;, please do not hesitate to <br />contact ROCKY MOUNTAIN GEOTECHNICAL. <br />' Sincerely, <br />ROCKY F7 UNTAIN G TECHNICAL <br />' K nne h L. P.E. <br />KLM/bm <br />encl. <br />t The Railroad Station • 555 E. Pikes Peak Avenue, Suite 107 • Colorado Springs, Colorado 80903 • (303) 634-1999 <br />