Comparison of Becker Penetration Test Interpretation Methods in Characterization of Gravelly Soil Deposits

The instrumented Becker Penetration Test (iBPT) system and interpretation method were utilized in January 2016 during the site investigation phase of a large infrastructure project in Vancouver, British Columbia, Canada. One iBPT sounding was conducted at 1.2 - 4.2 m spacing from previously conducted Standard Penetration Test (SPT), Cone Penetration Test (CPT) and Sonic soundings. The iBPT equivalent N60 values were found to agree well with those measured in the adjacent SPT soundings which provided a site-specific verification of the previously developed iBPT-SPT correlation. Additionally, the Becker Penetration Test (BPT) interpretation methods of Harder & Seed (1986) and Sy & Campanella (1994) were utilized and compared to the iBPT and SPT data. Harder & Seed (1986) estimated N60 values were consistently lower than both the iBPT estimated and SPT measured N60 values. The N60 values estimated via the Sy & Campanella (1994) method either agreed with or were higher than the iBPT estimated and SPT measured N60 values. The overly- and non-conservative driving resistances estimated by the two BPT interpretation methods, respectively, are consistent with the indirect techniques each method uses to separate the tip resistance from the total driving resistance. Overall, the iBPT data gathered at the Vancouver project site demonstrates the potential for the iBPT to be employed as an accurate means of characterizing gravelly soil deposits.