Effect of Cold Temperature on Shear Strength and Consolidation Properties of Deep Water Soft Marine Clays

在挪威海和许多其他极北方或南方纬度的近海地区，深水位置的海床温度持续在0 °C左右，孔隙流体的含盐量使土壤保持不冻结。在这些地区，海上设施的设计通常受波浪或浮冰产生的大横向载荷的情况控制，在这些情况下，软弱的表层土壤成为关键部件。精确估算土壤强度和固结特性，避免不必要的保守性，可以节省大量的施工和安装费用。以往的研究表明，随着温度的降低，前期固结压力的增加和不排水抗剪强度的增加对粘性土有显著的影响。然而，以前的工作还没有对来自低温环境的样品进行，这些样品在取样、储存和测试期间保持在冷的原位温度。以往的工作表明，允许样品升温到室温，然后再冷却到冷原位温度可能会导致高估的不排水抗剪强度和预固结压力。本项目将比较温度对从低温环境中采集的样品的实验室强度和固结性能的影响，这些样品在取样、储存和测试期间保持在冷的原位温度下，而这些样品则储存在室温下，然后在冷的原位温度和室温下进行测试。将对两种不同塑性指数的粘土进行评估。这项工作将与挪威奥斯陆的挪威岩土工程研究所合作完成，通过认识低温对强度和固结性能的影响，有可能通过降低建筑和安装成本来影响工业。此外，该项目的结果有可能通过取样、处理、储存和测试实践来影响工程实践，这些实践可以解释低温对软粘土性质的影响。

In the Norwegian Sea and in many other extreme northern or southern latitude offshore areas, the temperature at the seabed in deep-water locations is continuously around 0 °C with the salt content of the pore fluid allowing the soil to remain unfrozen. The design of offshore facilities in these regions is generally governed by cases involving large lateral loads from waves or floating ice where the weak surficial soils become critical components. A precise estimate of soil strength and consolidation properties that avoids unnecessary conservatism can result in substantial construction and installation savings. Previous work has shown a significant effect of increasing preconsolidation pressure and increasing undrained shear strength with decreasing temperature for clay soils. Previous work has not, however, been performed on samples from cold temperature environments that have been maintained at cold in situ temperatures during sampling, storage and testing. Previous work indicates that allowing samples to warm to room temperature and then recooling to cold in situ temperatures may result in an overestimation of undrained shear strength and preconsolidation pressure. This project will compare the effect of temperature on laboratory strength and consolidation properties for samples taken from cold temperature environments that have been maintained at cold in situ temperature during sampling, storage and testing to those that have been stored at room temperature and then tested at both cold in situ temperature and room temperature. Two clays of different plasticity indices will be evaluated.This work will be done in collaboration with the Norwegian Geotechnical Institute, Oslo Norway, and has the potential to impact industry through reduced construction and installation costs by recognizing the effects of cold temperature on strength and consolidation properties. In addition, results from this project have the potential to impact engineering practice through sampling, handling, storage and testing practices that can account for the effect of cold temperature on soft clay properties.