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首页> 外文会议>ASME international conference on ocean, offshore and arctic engineering >GEOTECHNICAL INVESTIGATION OF PORE PRESSURE BEHAVIOR OF MUDDY SEAFLOOR SEDIMENTS IN AN ARCTIC PERMAFROST ENVIRONMENT
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GEOTECHNICAL INVESTIGATION OF PORE PRESSURE BEHAVIOR OF MUDDY SEAFLOOR SEDIMENTS IN AN ARCTIC PERMAFROST ENVIRONMENT

机译：北极多年冻土环境中泥质海底沉积物孔隙压力行为的岩土工程研究

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Herschel Island, Yukon, Canada, is made of ice-rich permafrost and is affected by high rates of coastal erosion, likely to increase with decreasing summer sea ice extent. During an interdisciplinary expedition to Herschel Island in July 2014, geotech-nical investigations were carried out in shallow water environments of up to 20 m water depth and at different beaches. The free-fall penetrometer BlueDrop was deployed at 299 positions. Apart from obtaining vertical profiles of sediment strength and the pore pressure response upon impact, the pore pressure evolution over a period of one hour after deployment was investigated. The focus area for these tests was Pauline Cove, located at the south-eastern side of the island, being sheltered by a spit from the open Beaufort Sea and affected by a number of old and young retrogressive thaw slumps, delivering large amounts of mud. The sediment resistance profiles revealed up to three distinct layers of sediment strength, expressing different consolidation states, or possibly changes in sediment composition. This stratification was supported by the pore pressure results, including pore pressure evolution "on-the-flight" during penetrometer penetration as well as pore pressure evolution at maximum penetration depth with the penetrometer being at rest. The sediment surface layer 1 was characterized by a thickness of 5-20 cm depending on the respective location, low sediment resistance and predominantly hydrostatic pressure. It most likely has frequently been reworked by wave action, and exhibited sim- ilar geotechnical signatures as fluid mud. Layer 2 reached sediment depths of 30-60 cm, showed an increase in sediment resistance and distinct subhydrostatic pore pressures during penetration, while pore pressures increased in an asymptotic manner to suprahydrostatic (160-180% of hydrostatic pressure) over an observation period of 30-50 minutes. Based on comparison to other examples from the literature, it was hypothesized that layer 2 was composed of overconsolidated mud. Layer 3 featured a significant increase in sediment resistance as well as pore pressure during penetration. As soon as the probe came to rest, the pressure decreased significantly to subhydrostatic conditions, before swinging back to being suprahydrostatic and then slowly dissipating. A similar behavior has been associated to silty sands and high bulk densities. Here, it may suggest a change in sediment composition, likely influenced by coarser nearshore and beach sediments, representing also a denser sediment matrix. The pore pressure results will complement the geological and geotechnical characterization of the coastal zone of Hershel Island, and contribute to the investigation of erosion and deposition processes.
机译：加拿大育空地区的赫歇尔岛（Herschel Island）是由富含冰层的多年冻土制成，并受到沿海侵蚀的高比率的影响，并可能随着夏季海冰面积的减少而增加。在2014年7月的一次对Herschel岛的跨学科考察中，对水深不超过20 m的浅水环境以及不同的海滩进行了地质技术调查。自由落体渗透仪BlueDrop部署在299个位置。除了获得沉积物强度和冲击后孔隙压力响应的垂直剖面图，还研究了展开后一小时内的孔隙压力演变。这些测试的重点区域是位于岛东南侧的波琳·科夫（Pauline Cove），周围是开阔的波弗特海（Beaufort Sea）吐出的水，并受到许多老少皆宜的退缩解冻物的影响，输送大量泥浆。泥沙抵抗特征揭示了最多三个不同的泥沙强度层，表现出不同的固结状态，或者可能是泥沙成分的变化。孔隙压力结果支持了这种分层，包括渗透计渗透过程中“飞行中”的孔隙压力演化以及渗透计处于静止状态时在最大渗透深度的孔隙压力演化。沉积物表面层1的特征在于5-20cm的厚度，这取决于相应的位置，低的沉积物阻力和主要的静水压力。它很可能经常受到波浪作用的影响而重新加工，并表现出类似岩土的流体泥浆特征。第2层达到30-60 cm的沉积物深度，在渗透过程中显示出沉积物抗性的增加和明显的亚静水孔隙压力，而在30观察期内，孔隙压力以渐近方式增加至超静水压力（静水压力的160-180％）。 -50分钟。根据与文献中其他示例的比较，假设第二层由超固结泥浆组成。第3层的特点是渗透过程中的抗泥沙性和孔隙压力显着增加。探针静止后，压力会显着下降至亚静水压状态，然后再回到超静水压状态，然后逐渐消散。类似的行为与粉砂和高堆积密度有关。在这里，这可能表明沉积物成分发生了变化，这可能受到较粗糙的近岸和海滩沉积物的影响，这也代表了较密集的沉积物基质。孔隙压力的结果将补充Hershel岛沿海地区的地质和岩土特征，并有助于研究侵蚀和沉积过程。

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