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105_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

105_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - =...

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where a' = overburden pressure in bars and N fie1d = N ss BC21 Be Soil Parameters: Need c, C u (= SU), cjl', cjlu, "(to use in BC formulae o Evaluate from field samples in lab: triaxial tests, direct shear tests, unconfined compression o Educated guess for clays: correlations between plasticity or liquidity index vs. C u Educated guess for sands: correlations between relative density I unit weight vs. cjl as f(a') o Guess based on local experience, water content, previous tests (nice, warm fuzzy feeling) o Evaluate from SPT: Bowles tables (1996) for C u and cjl vs. N (see insitu notes, very approximate) Wolff (1989), see Das: $0 = 27.1 0 + 0.3N 1 - 0.00054N~ where N 1 = CN Nfield and Nfield = Nss Schmertmann (1975), Kulhway & Mayne (1990), see Das: [ N ]0.34 tancjl= field 12.2 +20.3a' o Evaluate from Cone Penetrometer (CPT): based on cone tip bearing pressure, qc Schmertmann (1975)'c = s = qc -Po U U N k where Po = "(Z = total stress at depth of test N k = CPT Bearing Factor = 10-20, typically use 15 Nk lower with higher sensitivity = SI = (su )UndiSIUlbed (su )remo!ded see Bowles chart (insitu
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Unformatted text preview: = SI = (su )UndiSIUlbed (su )remo!ded see Bowles chart (insitu notes, after Lunne & Eide, 1976) for N k from the plasticity index, I p = (LL- PL) • Schmertmann (1975), Kulhway & Mayne (1990), see Das and chart in insitu notes: tan$ = 0.1 +0.3810 9 ( ~~ ) where a' = effective overburden pressure o Vane Shear Test (VST) for direct measurement of C u o Iowa Borehole Shear Test (IBST) direct measurement of Co and cjl o Marchetti Dilatometer (DMT) for estimate of C u based on initial, lateral lift-off pressure, and cjl based on thrust and initial lateral lift-off pressure o Pressuremeter Test (PMT) for C u based on limit pressure PL and shear modulus G p-a c =s = L ho U U N p where aha = total horizontal stress at depth of test N p = 1 +lnQ. (:.iterative solution for cu) C u...
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