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doi:10.2204/iodp.proc.308.213.2009

Introduction

Integrated Ocean Drilling Program (IODP) Expedition 308 focused on how geology, pressure, and stress couple to control overpressure and fluid flow on the Gulf of Mexico continental slope (see the “Expedition 308 summary” chapter). To achieve this study, four sites were drilled and cored in two distinct areas in the Gulf of Mexico (Fig. F1). Two sites (U1319 and U1320) were drilled in a normally pressured area, Brazos-Trinity Basin IV (Fig. F2). The other two sites (U1322 and U1324) were drilled in an overpressured area, Ursa Basin (Fig. F3).

Whole-core geotechnical samples were taken at each of the four sites (U1319, U1320, U1322, and U1324) for the purpose of performing shore-based consolidation tests. To determine which soil samples to use for the experiments, noninvasive imaging was needed to evaluate the structure of the sample. This imaging was done using radiographs and X-ray computed tomography (CT) scans.

Most of the Pennsylvania State University (PSU) and Massachusetts Institute of Technology (MIT) samples were X-rayed at MIT’s radiography facility. The Rice University samples were X-rayed by Fugro. The goal of imaging the soil was to qualitatively assess the presence of inclusions and variation in fabric, identify layering or inhomogeneities, and select undisturbed portions for experiments (Long et al.). Once the radiographs were completed they were shipped to PFS Photo in Christiansburg, Virginia, for digital conversion. X-ray CT scans were performed by the Center for Quantitative Imaging (CQI) at PSU.

Tables T1 and T2 contain information on the 151 radiographs (Table T1) and 12 X-ray CT scans (Table T2) that were performed on the whole-core samples. These tables include sample identifiers such as, site, hole, core, and section. They also include the sample depth in meters below seafloor (mbsf) and the length of the sample in centimeters, including the top and bottom measurements. These data are used to pinpoint the exact location of the sample in the image with respect to the whole core. Samples were recovered by advanced piston corer (APC) or extended core barrel (XCB) technology. During APC, two different cutting shoes were used: the “Fugro” and “IODP-APC” cutting shoes. The Fugro cutting shoe has a thinner kerf than the IODP-APC cutting shoe and was used to try and reduce deformation during coring. Also listed in Tables T1 and T2 are the samples that were used for constant rate of strain consolidation (CRS) experiments (Long et al.). The individual digital images (.pdf format) can be found in “Supplementary material.”