KIYOFUMI, SUZUKI
Japan National Oil Corporation, Chiba, Japan

Abstract: Deformation Processes of Unconsolidated Sediments: An Experimental Study

An experimental study was carried out in order to understand deformation processes of unconsolideted sediments. It was found that kaolin clays were compacted and/or unloaded under KO conditions close to natural conditions. Shear tests were made using an tri-axial apparatus after compaction with or without unloading. Data such as stress, strain, confining pressure and pore pressure were collected from the undraind shear test until the axial strain reached 20-25%. After shearing, deformational structures were described. Photographs of the outer shapes of specimens were taken before cutting perpendicular to s2. The etched section of a specimen was profiled and photographed. In some cases, SEM images were used for examining the internal structures on freeze-dry samples. From the results of experiments, the following results were obtained. The sediments that have solid framework were strained laterally synchronized with reacted vertical strain, while less lithified sediments only compacted vertically. The consolidated sediments showed microcracks at the first stage of shear; however, the latter did not generate fractures at first, although, they generated faults with preferred orientation of clay minerals at last. Results of the experiments can be explained on the account of stress anisotropy, pore pressure and the strain rate. Based on these results, the deformation diagram for unconsolidated sediments has been defined experimentally.

AAPG Search and Discovery Article #90920©1999 AAPG Pacific Section Meeting, Monterey, California