Geotechnical properties of shelf sdiments from the Prydz Bay@en

This paper presents a geotechnical characterization of the glacigenic sediments in Prydz Bay, East Antarctica, based on the shipboard physical properties data obtained during Leg 119, combined with results of land-based analyses of 24 whole-round core samples. Main emphasis is placed on the land-based studies, which included oedometer consolidation tests, triaxial and simple shear tests for undrained shear strength, permeability tests in oedometer and triaxial cell, Atterberg limits, and grain-size analyses. The bulk of the tested sediments comprise overconsolidated diamictites of a relatively uniform lithology. The overconsolidation results from a combination of glacial loading and sediment overburden subsequently removed by extensive glacial erosion of the shelf. This leads to downhole profiles of physical properties that have been observed not to change as a function of the thickness of present overburden. A number of fluctuations in the parameters shows a relatively systematic trend and most likely results from changes in the proximity to the ice sheet grounding line in response to variations in the glacial regime. Very low permeabilities mainly result from high preconsolidation stresses (Pc'). Pc' values up to 10,000 kPa were estimated from the oedometer tests, and empirical estimates based on undrained shear strengths (up to 2500 kPa) indicate that the oedometer results are conservative. The diamictites generally classify as inactive, of low to medium plasticity, and they consolidate with little deformation, even when subjected to great stresses. […]本文针对南极东部普里兹湾的冰成沉积物（glacigenic sediments）开展岩土特性表征研究，所用数据源自Leg 119航次获取的船载物理性质测试结果，并结合24块整芯样品的陆上分析结果。本研究重点聚焦陆上分析工作，涵盖固结仪（oedometer）固结试验、用于测定不排水抗剪强度的三轴（triaxial）及单剪试验、固结仪与三轴腔体内渗透性测试、阿特伯格界限（Atterberg limits）测试以及粒度分析（grain-size analyses）。本次测试的沉积物主体为岩性相对均一的超固结混杂岩（overconsolidated diamictites）。该超固结作用由冰川加载，以及后续经陆架广泛冰川侵蚀剥除的沉积物上覆荷载共同导致。这使得物理性质的井下剖面未随当前上覆荷载厚度发生变化。各项参数的多处波动呈现出相对系统的变化趋势，其极有可能源于冰川状态变化引发的与冰盖接地线（ice sheet grounding line）的距离变化。极低的渗透性主要源于高前期固结压力（preconsolidation stresses, Pc'）。固结仪测试估算得到的Pc'值可达10000 kPa，而基于不排水抗剪强度（最高可达2500 kPa）的经验估算结果表明，固结仪测试结果偏保守。该类混杂岩总体可归类为低-中等塑性的非活性沉积物，即便承受极高应力，其固结变形量也极小。……