Case History of Installing Instrumented Jacked Open-Ended Piles

Abstract

Construction effects on pile-soil systems arise from the process of installing displacement piles. This study conducted a comprehensive field test program complemented with laboratory tests to observe the performance of jacking open-ended concrete pipe piles into silt deposits. The jacked piles were examined in a plugged mode during installation. Direct observation on the soil plugs reveal that their formation generally accords with the stratigraphic nature of the layered soils. Soil-arching behavior during pile penetration causes the soil in the shear zone along the inner pipe wall to mainly come from the uppermost layer of the deposit. Laboratory tests on the soil plug shows evident compaction and the tendency increased strength over time. The buildup of the excess pore pressure and radial total stress in the soil is sensitive to the jacking installation procedure. By taking into account the soil displacement related to the plugging degree, the captured peak excess pore pressure at a given horizon can be modeled by the cavity expansion theory that normally adapts to closed-ended pile. The jacking annulus resistance normalized by the cone tip resistance is independent of the penetration depth and the degree of plugging. A considerable portion of the annulus resistance is locked in the pile after installation, decreases a little during adjacent pile installation, and remains stable over a long period.