Liquefaction evaluation discrepancies in tropical lagoonal soils |
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Authors: | Peter G Nicholson |
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Institution: | (1) Associate Professor, and Graduate Chair, Department of Civil and Environmental Engineering, University of Hawaii at Manoa, 2540 Dole Street, Honolulu, Hawaii |
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Abstract: | Field penetration tests and shear wave velocity measurements are both established and accepted methods for evaluating liquefaction
potential in soils. The results produced by the two methods are generally well correlated. However, recent studies have shown
that when investigating tropical lagoonal deposits, the same accepted methods for evaluating liquefaction potential often
produce significant discrepancies in results. This discrepancy is most apparent in saturated lagoonal deposits of calcareous
gravelly sand (or sandy gravel), which tend to exhibit low penetration resistance values but relatively high shear wave velocities.
These disparate test results can suggest different soil classifications under current building codes. Ambiguity in the code
may allow for a potentially unconservative classification, which may in turn allow for the use and construction of less costly,
lighter weight foundation systems than warranted. Equally as important, the potential for unconservative design as related
to liquefaction appears to be high when shear wave velocity measurements are used as a basis for evaluation in these types
of lagoonal deposits. Because of this, it is strongly recommended that caution should be excercised when determining seismic
design parameters in these types of geologic environments. A hypothesis to explain the discrepancies in the results of evaluation
methods and a suggested design protocol is proposed. |
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Keywords: | building codes calcareous soils liquefaction penetration tests shear wave velocity |
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