81_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

81_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - q to...

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ps4 Notes on Schmertmann Method: o Interpolate idealized I z distribution for footings with 1< UB < 10: o initial Iz 0.1 ~ 0.2 o depth of Izp 0.5B ~ B o maximum depth of Iz influence 2B ~ 4B o Interpolate modulus, E, for footings with 1 < UB < 10: E ~ 2.5qc ~ 3.5 qc a Developed for NC sands - generally conservative if sand is preloaded, compacted, etc. o Applies to static loading only, dynamic loads can create large pore pressures and 'Significantly decrease effective stresses leading to large deflections o Can use NSPT to estimate qc if no CPT data available. This is a common and generally conservative procedure, but there is significant uncertainty due to the variability of the
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Unformatted text preview: q, to estimate N). The ratio (qc / Ns PT ) increases as the mean grain size increases. Chart from Robertson et al. (1986) expands earlier work by Schmertmann: N 60 blowslft or blows/0.3m (60% energy) rJ(,# fr~", l~(~k, 1,/.,. ........ [< $PT qc in bars (1 bar = 1.044 tsl = 100 kPa) Note that cemented sands (common in FL) can have (qc / N 60 ) > 10. Soil Type qc/ N 60 Sensitive Clays 2 Organic Soils 1 Clay 1 Clay to Silty Clay 1.5 Silty Clay to Clayey Silt 2 and Clay-Silt-Sand mix Clayey Silt to Sandy Silt 2.5 Sandy Silt to Silty Sand 3 Silty Sand to Sand 4 Sand 5 Sand to Gravelly Sand 6...
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