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• WHEXSIopeEvaluation AdrianBrown <br />The granitic value is the average of two sets of triaxial tests, with the results being 2.0 (foliated rock) and <br />17.0 (microgranite), which have been averaged. The expected value is 4-8 (Hoek, 2001). Due to the rock <br />foliation, considerable variation is expected in this pazameter. <br />3.2.4 Summary of strength testing <br />Based on these above results, the following is concluded about the unconfined compressive strength of <br />the principle mine materials (excluding latite dike material.): <br />1. The average unconfined compressive strength of the intact rock materials is approximately <br />13,000 psi (91 MPa) for both of the principal materials in the WHEX Mine azea (volcanics <br />and granites). <br />2. The average Hoek-Brown m; value for the site rocks is about 9; while this shows wide <br />variation, both rock types aze similaz. <br />• <br />The UCS can be used to classify the rock strength. Hoek (2001) presents a rock strength classification <br />based on the UCS, which is summarized in Table 4. Based on this classification, the unconfined <br />compressive strength of the WHEX rock samples are on average "Moderately Strong Rock (R3)". <br />Table 4. Approximate Classification of Rock <br />UCS RANGE CLASS STRENGTH DESCRIPTION <br />150-3,500 psi Rl Very weak rock Crumbles under sharp blows with geological <br /> ick oint, can be cut with ocket knife. <br />3,500 - 7,500 psi R2 Moderately weak rock Shallow cuts or scraping with pocket knife <br /> with difficulty, pick point indents deeply with <br /> firm blow. <br />7,500-15,000 psi R3 Moderately strong rock Knife cannot be used to scrape or peel surface, <br /> shallow indentations under firm blow from <br /> ick oint. <br />15,000-30,000 psi R4 Strong rock Hand-held sample breaks with one firm blow <br /> from hammer end of eolo 'cal ick. <br />> 30,000 psi RS Very strong rock Requires many blows from geological sample <br /> to break intact sam le. <br />Source: Hoek and Bray, 1980, Table II, p. 99 <br />• <br />3.3 Frictional Properties <br />3.3.1 Laboratory tests <br />The frictional chazacteristics of discontinuities (joints and faults) in the volcanic WHEX rocks has been <br />established by adopting testing results from volcanic materials in previous studies. <br />Report 1385L.200309017 6 <br />