裂隙非水相液体迁移细观机制与基岩含水层污染场地评价

Non-aqueous phase liquids released into bedrock aquifers present an important scientific problem in groundwater contamination and remediation. The overall goal of the proposed project is to obtain a fundamental understanding of NAPL migration in fractured media through a combination of laboratory experiments, numerical simulation, and theoretic analysis. The project first explores the micro-scale mechanisms of water−NAPL immiscible displacement in rough-walled fractures, aiming to elucidate the combined effect of various factors, including fracture roughness, wettability, fluid properties and hydrodynamic conditions, on NAPL invasion patterns and displacement regimes. Then the transitions between different NAPL migration regimes will be explored and a phase diagram of two-phase flow regimes in fractures will be proposed in light of experimental data and numerical simulations. Macro-scale constitutive relations of water−NAPL two-phase flow that take into account the aperture statistics and the interfacial patterns will also be proposed. The results and theory obtained from the micro-scale studies will be applied to the problem of evaluating NAPL contamination in bedrock aquifers through field scale numerical simulations based on discrete fracture network model. An improved understanding of two-phase flow in fractures is of general interest to the geosciences community, and critical to the development in the field of coupled processes in fractured rocks. In addition, the proposed study will provide a theoretical framework and a practical guidance for control of two-phase flow in fractured media with a number of important engineering applications.

裂隙含水层非水相液体（NAPL）污染是地下水环境管理与修复领域的前沿和难点问题。本项目围绕基岩裂隙含水层NAPL-水两相流特性与NAPL迁移机制关键科学问题，采用实验、理论分析和数值模拟相结合的方法，开展岩石裂隙NAPL−水两相流细观机理研究，揭示裂隙几何形貌、湿润性、流体性质等因素对NAPL−水两相流界面形态及其演化规律的影响，提出多因素联合作用下NAPL−水两相驱替模式转变的临界条件，建立反映裂隙开度分布和湿润性影响的驱替模式相图；研究粗糙裂隙两相流的均匀化方法，建立反映裂隙粗糙度和湿润性的NAPL−水两相渗流宏观本构关系，研发基岩裂隙含水层NAPL迁移数值分析方法和模拟平台，阐明裂隙网络特征、污染源位置及强度、地下水径流条件等因素对含水层NAPL迁移过程的影响，进而依托典型裂隙含水层开展场地评价和污染防控策略研究，为我国地下水有机物污染风险评估、污染控制及修复治理提供理论与技术支撑。

裂隙含水层非水相液体（NAPL）污染是地下水环境管理与修复领域的前沿和难点问题。本项目围绕裂隙介质NAPL-水两相流细观机理与宏观迁移特性关键科学问题，采用室内实验、理论分析和数值模拟相结合的方法，取得了如下研究结果：（1）开展了岩石孔隙与裂隙两相流的可视化实验和细观尺度数值模拟研究，揭示了裂隙几何形貌、湿润性、流体性质、流速、悬浮颗粒等因素对两相流界面形态及其演化规律的影响，提出了粗糙裂隙两相流驱替模式转变的临界条件和反映裂隙开度分布和湿润性影响的驱替模式相图；2. 开展了基于两相流界面时空演化规律的流体压力和流速均匀化方法研究，建立了考虑粗糙度、各向异性等因素影响下的裂隙两相相对渗透系数与饱和度−毛细压力曲线模型；3. 开展了细观尺度NAPL增溶、原位氧化等修复技术的实验研究，揭示了修复过程中孔隙尺度溶质运移、相间物质转移、化学反应的机理；4. 开展了裂隙网络两相渗流可视化实验研究，揭示了裂隙发育特征、连通性等因素对污染液体宏观迁移动态特性的影响机理，提出并验证了污染液体穿透时间理论模型；5. 研发了含水层两相渗流与污染物运移数值模拟分析平台并开展了模拟研究，揭示了介质结构特征、污染源位置与强度等因素对污染迁移规律的影响规律。研究成果可为我国地下水有机物污染风险评估、污染控制及修复治理提供理论与技术支撑。在项目资助下，项目组成员在Environmental Science & Technology、Geophysical Research Letters、Water Research、Water Resources Research等国际著名期刊发表SCI收录论文13篇、EI收录和核心期刊论文4篇，授权国家发明专利2件，培养博士毕业生7人和硕士毕业生2名。