Analysis of Large Diameter Pipe Pile Drivability in Tokyo Bay Using Piezocone Data

Abstract

The piezocone penetration test (CPTU) provides near continuous measurements of three independent parameters: tip resistance (q t ), sleeve friction (f s ), and penetration pore pressure (u 2 ). The tip resistance and sleeve friction are roughly analogous to pile end bearing resistance (q b ) and the shaft resistance (τ f ) near the pile tip during installation, respectively, while the penetration pore pressure provides an indication of the drainage conditions during cone penetration. However, due to the differences in diameter between a pile and a CPT, as well as the differences in installation method, CPTU parameters (q t and f s ) must be modified to assess the values of unit base and shaft resistance (q b and τ f ) applicable to the static capacity of the pile and the soil resistance to driving (SRD). In this paper, back-analyses of installation records from eight large diameter (1.2 to 1.8m) open ended pipe piles driven through soft clays, silts, and sands at the Tokyo Port Bay Bridge site are conducted using the results of adjacent CPTUs. These analyses provide guidance on evolving methods for interpreting CPTU data to provide predictions of short term SRD, in addition to long term static capacity.