In-Situ Pile Segment Model Experiments at Harvey, Louisiana

Abstract

Abstract Three field experiments have been conducted in normally consolidated soft clay at Harvey, La. using instrumented 3inch diameter probes to simulate pile behavior under a variety of static and cyclic axial loadings. Lateral total pressure and pore pressure were observed and shear transfer versus pile displacement were recorded. The results represent the first phase of a comprehensive program to develop an improved basis for pile design. Introduction As a part of a comprehensive program of research into the behavior of friction piles in clay, in situ pile segment models, or probes, have been developed to measure total radial pressure, pore pressure, shear transfer, and relative pile-soil displacement during installation, consolidation, and static and cyclic axial loading. The experiments reported herein were the first of 47 experiments performed with the probes, which have included tests at the onshore sites of two large-diameter instrumented pile load tests, the offshore site of load tests on instrumented large-diameter driven and drilled-and-grouted piles, and three onshore sites where parallel large-diameter pile load tests are not available. Four of the six sites contain soft-to-stiff normally consolidated clays. At the four sites, a total of 42 experiments were performed, with load testing at times ranging from minutes to three months after installation. The data are believed to represent a sound basis for developing a fundamental understanding of pile-soil interaction and for developing reliable design procedures for the design of pile foundations subjected to static and cyclic axial loading. Methods The pile segment models were developed at The Earth Technology Corporation (Refs 1 and 2). Two sizes, 3.00 and 1.72 inches in diameter, have been built and utilized in field tests at various locations. The 3-inch size permits investigation of various cutting shoes or end conditions and is the type employed for the tests reported in this paper. The features of the 3-inch probe and the three stages of installation are shown in Fig 1. The tool is impact-driven or jacked into the soil beyond the end of a drilled hole. The leading section is a tube which is long enough to simulate the effects of an open-end pile in the zone where the instrumented section comes to rest. Various wall thicknesses or a fully plugged condition can be utilized. At the slip joint shown at the left, the leading section is free to move one inch with respect to the instrumented section and the relative movement is indicated with an internal displacement transducer. After installation, the leading section serves as an anchor for accurate measurement of pile-sail displacement. Soil shear transfer is measured as the differential reaction between the two load cells. The pressure measurements aid in interpreting soil consolidation and set-up processes, plus pore water and structural changes during shear.