寒区埋地石油管道泄漏引起的冻土退化和管基土劣化机理研究

Oil spilled from the buried pipeline can cause both serious environmental and engineering problems in cold regions. So far, there is less research on processes and mechanisms of permafrost degradation and foundation soil deterioration induced by spilled oil. Aiming at the above two problems, this research project will conduct some seepage tests to study oil’s flow properties in porous media at some low temperatures and establish its equation of motion according to theories of permafrost science and engineering, dynamics of fluids in porous media and environmental geotechnology. The monitored data of thermal regime of degrading permafrost and oil contamination in field and the measured data of thermal parameters of oil-contaminated soils in laboratory are combined to study the process and mechanism of permafrost degradation induced by oil contamination. Relationships between macroscopic and microscopic properties of oil-contaminated soils with different oil contents are used to study the process and mechanism of deterioration of foundation soils induced by oil contamination. There are a certain breakthroughs and innovations about the research contents, method, and theory in this research project. The expected results will have some scientific and practical merits, which will provide solid basis for evaluating the spilled oil contamination, for analyzing the stability of the China-Russia Crude Oil Pipeline, for selecting some mitigative measures, and for developing the new discipline of environmental geotechnology in cold regions.

寒区埋地管道原油泄漏会造成严重的环境污染和工程失稳问题。目前，对于石油泄漏引起的冻土环境演化过程和机理及管基土劣化机理研究很少。本项目拟以中俄原油管道面临的这两个实际问题为背景，结合冻土学、渗流力学和寒区环境岩土工程理论，通过不同温度条件下的低温石油渗透试验，研究低温石油渗透规律和特点，建立低温石油渗流运动方程；利用现场石油污染与冻土退化监测资料和室内石油污染影响土体热参数试验来研究石油泄漏引起的冻土退化过程和机理，利用不同石油含量污染土体工程特性变化和细微观结构变化从宏观和细微观角度全面揭示石油泄漏引起的管基土强度劣化过程和机理。项目在研究内容、试验方法、基础理论等研究方面都有一定的突破和创新，具有重要的科学意义和实用价值。研究成果为中俄原油管道石油泄漏污染评价、管道稳定性分析以及防治和治理技术选择等提供重要的理论基础和技术支撑，为发展寒区环境岩土工程奠定重要基础。

中俄石油管道投产运营后，多年冻土区石油泄漏引起的环境问题和管道稳定问题已经成为亟待研究的关键问题。本研究开展非等温石油渗流试验和渗透试验并研究多年冻土区温度梯度对石油迁移的影响。结果显示温度的降低引起石油粘度增加以及土颗粒吸附有机质能力增强是削弱石油在土体中的渗透能力的主要因素。石油污染土导热系数和冻结温度试验研究表明石油污染土体导热系数变化机制主要由油、水在土骨架结构中所赋存的位置、相对含量、相状态和自身导热性能共同决定；石油对冻结温度的影响程度取决于含水量的高低。研究结果揭示了多年冻土区石油污染冻土退化机理。低温三轴压缩试验和三轴蠕变试验研究表明石油污染可以显著降低冻土的强度，石油的存在改变了颗粒间（土颗粒与土颗粒以及土颗粒与冰颗粒）的胶结作用是冻土强度变化的重要原因；在蠕变试验条件下石油污染对冻土蠕变特征的影响主要表现在初始衰减蠕变阶段，应变随应力水平的增加快速增大；随着试验时间的推移并未出现明显的加速蠕变阶段。研究结果揭示了管基土劣化规律和影响因素，为石油污染管基土的防治提供基本参数和科学指导。