HR: 11:40h
AN: OS32A-06    [Abstracts]
TI: Bubbles in Sediments: Visualization, Measurements and Modelling
AU: * Boudreau, B P
EM: bernie.boudreau@dal.ca
AF: Dept. Oceanography, Dalhousie University, Halifax, NS B3H4J1 Canada
AU: Johnson, B S
EM: bruce.johnson@dal.ca
AF: Dept. Oceanography, Dalhousie University, Halifax, NS B3H4J1 Canada
AU: Barry, M
EM: barrym@dal.ca
AF: Dept. Oceanography, Dalhousie University, Halifax, NS B3H4J1 Canada
AU: Algar, C
EM: calgar@dal.ca
AF: Dept. Oceanography, Dalhousie University, Halifax, NS B3H4J1 Canada
AU: Reed, A
EM: allen.reed@nrlssc.navy.mil
AF: Naval Research Laboratory, Code 7431, Stennis Space Center, Stennis, MS 39529 United States
AU: Furukawa, Y
EM: yoko.furukawa@nrlssc.navy.mil
AF: Naval Research Laboratory, Code 7431, Stennis Space Center, Stennis, MS 39529 United States
AB: Free gas bubbles constitute a common fluid phase in nearshore and continental margin sediments. X-Ray computed tomographic images show that injected bubbles in muddy, cohesive sediments are eccentric oblate spheroids (disks) that grow either by fracturing the sediment or by re-opening pre-existing fractures. In contrast, bubbles in sandy, non-cohesive sediments tend to be spherical, suggesting that sand acts plastically or fluid-like in response to growth stresses. The shape and eccentricities of such bubbles are entirely consistent with the predictions from linear elastic fracture mechanics (LEFM). Given that muddy sediments are elastic and fracture, it becomes much easier to explain physically related phenomena such as seafloor "pockmark" formation and animal burrowing. Correct modelling of bubbles in muds requires in situ measurement of appropriate geo-mechanical properties, i.e., Young's modulus and the critical stress intensity factor, as well as the in situ gas saturation. We are developing instruments to acquire such data.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 1051 Sedimentary geochemistry
DE: 3094 Instruments and techniques
DE: 4804 Benthic processes, benthos (0408)
DE: 4820 Gases
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005