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I <br />~' TABIF 2 <br />APPROXIMATE CLASSIFICATION OF COHESIVE SOIL AND ROCK (ROBERTSON, 1987) <br />1 <br /> <br />i1 <br />I' <br />~1 <br />~' <br />1 <br />1 <br />~~ <br /> <br />1 <br /> <br />c.' <br />1 <br />1 <br />No. Description Uniaxial compressive strength Examples ~ <br /> Ib/in2 kg/cmZ MPa <br />S7 VERY SOFT SOIL -easily moulded <5 <0.4 0.04 <br />with fingers, shows distinct <br />heel marks <br />S2 SOFT SOIL -moulds with strong 5-10 0.4-0.8 0.04-0.08 <br />S3 FIRM SOIL -very difficult to 10-20 0.8-1.5 0.08-0.15 <br />mould with fingers, indented <br />with finger nail, difficult to <br />cut with hand spade <br />S4 STIFF SOIL -cannot be moulded 20-80 1.5-0.0 0.15-0.60 <br />with fingers, cannot be cu[ <br />with hand spade, requires hand <br />picking for excavation <br />SS VERY STIFF SOIL -very tough, 80-150 6-10 0.6-1.0 <br />difficult to move with hand <br />pick, pneumatic spade required <br />for excavation <br />R1 VERY WEAK ROCK -crumbles 1503500 10-250 1-25 ChalFr, rocksalt <br />under sharp blows wfth geological <br />pick point, can be cut with <br />pocket knife <br />R2 MODERATELY WEAK ROCK - 3500-7500 250-500 25-50 Coal, schist <br />shallow cuts or scraping with pocket siltstane <br />kn'rfe with difficulty, pick <br />point indents deeply with firm <br />blow <br />R3 MODERATELY STRONG ROCK - 7500-15000 500-1000 50-100 Sandstone, slate, <br />knife cannot be used to scrape or <br />peel surface, shallow indentations <br />under firm blow from pick point <br />R4 STRONG ROCK -hand-held sample 1500030000 1000-2000 100-200 Marble, granite, <br />breaks with one firm blow from gneiss <br />hammer end of geological pick <br />RS VERY STRONG ROCK-requires >30000 >2000 >200 Ouartxite, <br />many blows from geological pick dolerite, gabbro, <br />to break intact sample basalt <br /> <br />