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The Becker Penetration Test (BPT) is a widely used tool for the characterization of gravelly soils, especially liquefaction assessment. An instrumented Becker Penetration Test (iBPT) was developed and integrated into the standard, closed-ended Becker drill string. The iBPT produces a continuous profile of energy normalized blow count values, N B30 , which are computed using the acceleration and strain measurements recorded directly behind the driving shoe. The N B30 profile is repeatable and unaffected by hammer driving energy or accumulated shaft resistance. This paper presents the correlation between iBPT N B30 and SPT N 60 values which is necessary for performing liquefaction assessment in gravelly soils. In developing this correlation, field variability was addressed by comparing median iBPT N B30 and SPT N 60 values from adjacent soundings over geologically consistent depth intervals. A framework was also developed to assess, and, when appropriate, correct for gravel influence on measured SPT blow count (N) values. This framework utilizes SPT blows-per-inch as well as physical evidence from SPT and adjacent Sonic samples. The correlation between iBPT N B30 and SPT N 60 is shown to be a constant value of 1.8 and independent of soil type or penetration resistance magnitude. * Physical Evidence refers to soil gradations, sample photos and field logs from SPT split spoon samples and/or Sonic cores in the vicinity of the SPT sample.

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