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<br />EM lllO-2-l9l3 <br />31 Mar 78 <br /> <br />Table 2-5. <br /> <br />Preliminary Appraisal of Foundation Strengths <br /> <br />Method <br /> <br />1. Split-spoon penetration <br />resistance <br /> <br />2. Natural water content of <br />disturbed or general <br />type samples <br /> <br />3. Hand examination of dis- <br />turbed samples <br /> <br />4. Position of natural water <br />contents'relative to <br />liquid and plastic <br />limits <br /> <br />5. Torvane or pocket <br />penetrometer tests on <br />intact portions of <br />general samples or on <br />walls of test trenches <br /> <br />Remarks <br /> <br />l-a. Unconfined compressive strength, <br />tsf, of clay is about 1/8 of number of <br />blows per foot, or N/8, but consid- <br />erable scatter must be expected. <br />Generally not helpfUl where N is low <br /> <br />l-b. In sands, N values less than <br />about 15 indicate low relative densi- <br />ties. N values should not be used to <br />estimate relative densities for earth- <br />quake design <br /> <br />2. Useful when considered with soil <br />classification, and previous experi- <br />ence is available <br /> <br />3. Useful where experienced personnel <br />are available who are skilled in <br />estimating soil shear strengths <br /> <br />4-a. Useful where previous experience <br />is available' <br /> <br />4-b. If natural water content is close <br />to plastic limit foundation shear <br />strength should be high <br /> <br />4-c. Natural water contents near liquid <br />limit indicate sensitive soils usually <br />with low shear strengths <br /> <br />5. Easily performed and inexpensive but <br />results may be low; useful for pre- <br />liminary strength classifications <br /> <br />~. <br /> <br />2-l0 <br /> <br />e <br /> <br />. <br /> <br />~ <br /> <br />. <br /> <br />. <br /> <br />... <br /> <br />e <br />