HR: 1340h
AN: OS33B-0593    [Abstracts]
TI: Design of a Dual-Pressure Port Penetration Probe for Pore Pressure Measurements in Ocean Drilling
AU: * Long, H
EM: hlong@geosc.psu.edu
AF: The Penn State University, Department of Energy & Geo-Environmental Engineering, University Park, PA 16802
AU: Flemings, P B
EM: flemings@geosc.psu.edu
AF: The Penn State University, Department of Geosciences, University Park, PA 16802
AU: Germaine, J T
EM: jgermain@MIT.EDU
AF: Massachusetts Institute of Technology, Department of Civil & Environmental Engineering, Cambridge, MA 02319
AU: Chartier, M
EM: m_charti@MIT.EDU
AF: Massachusetts Institute of Technology, Department of Civil & Environmental Engineering, Cambridge, MA 02319
AB: We are building a tapered probe to measure pore pressure and hydraulic properties in low permeability sediments within boreholes. To minimize the time required for measurement we are using two pressure ports: one close to the narrow diameter tip and one on the large-diameter shaft. In-situ pore pressure is estimated within a short time by a two-point intersection method using the pressure dissipation recorded at the two pressure ports. A parametric study is presented to evaluate how possible changes in the probe geometry affects pore pressure dissipation at the pressure ports. The Strain Path Method (SPM) and a total stress soil model (MIT-T1) are used to predict the initial undrained pore pressure response upon insertion of series of hypothetical geometries. Uncoupled-isotropic consolidation is applied to simulate the subsequent excess pore pressure dissipation. The modeled response to insertion in normally consolidated Boston Blue Clay includes the following. Decreasing the length of the thin probe or increasing the diameter of the large shaft results in more rapid two-point intersection and a higher pressure at the two-point intersection. If the second pressure port is placed on the face of the tapered section, instead of the larger-diameter shaft, the intersection time is reduced. We are striving for a tool geometry that generates a consistent two-point intersection time that occurs as rapidly as possible in a range of soil properties.
DE: 5139 Transport properties
DE: 5194 Instruments and techniques
DE: 3094 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting