COLLABORATIVE RESEARCH: Evaluating Long-Term Impacts on Final Covers -- Exhumation of the ACAP Test Sections

摘要本研究的目的是评估成壤作用对垃圾填埋场最终覆盖层土壤和土工合成材料性质的影响，以及控制成壤变化的机制。这一目标将通过进行物理实验来实现，同时挖掘1999-2000年为替代覆盖评估方案(ACAP)建造的模拟最终覆盖的大规模测试部分。将在每个试验路段进行实地渗透系数测试，以确定饱和渗透系数的大小和变异性，并将进行染料和盐示踪剂试验，以评估优先流。这些试验的数据将使用考虑基质和优先流动路径之间耦合的可变饱和流动和传输模型进行分析，并使用收集的关于状态变量(基质吸力、含水率、温度等)的数据。将从不同位置和深度的每个试验段中取出大块样本，并进行试验，以评估水力特性在空间和尺度上的变化。将进行地貌制图，以提供有关土壤结构的定量信息，这些信息可用于解释水力特性变化的大小和尺度相关性。将进行植被调查，以评估物种分布、生根深度和密度以及其他影响蒸腾作用的特征的转变，并评估转变是否与土壤发生有关。研究结果将被用来确定影响覆盖物性能的物理、水文和生物机制，并提供对覆盖物随时间变化的洞察。吸取的经验教训将用于改进封面的设计和建造，并用于评估长期业绩。这些发现也将适用于其他水文问题(例如，自然补给、城市流域水文、工程景观中的渗透和径流)。通过跨学科和机构间合作加强学生学习，为中学环境科学课程开发水文学模块，以及通过招募多样化学生参加该项目，将产生更广泛的影响。

Abstract The objective of this study is to evaluate the effects of pedogenesis on the properties of soils and geosynthetics in landfill final covers and the mechanisms that control pedogenic changes. This objective will be met by conducting physical experiments while exhuming large-scale test sections simulating final covers that were constructed in 1999-2000 for the Alternative Cover Assessment Program (ACAP). Field hydraulic conductivity tests will be conducted on each test section to identify the magnitude and variability in saturated hydraulic conductivity, and dye and salt tracer tests will be conducted to assess preferential flow. Data from these tests will be analyzed with a variably saturated flow and transport model that accounts for coupling between the matrix and preferential flow paths, and using data collected regarding state variables (matric suction, water content, temperature, etc.). Large block samples will be removed from each test section at various locations and depths and tested to evaluate how the hydraulic properties vary spatially and with scale. Geomorphic mapping will be conducted to provide quantitative information on soil structure that can be used to interpret the magnitude and scale-dependence of changes in hydraulic properties. Vegetation surveys will be conducted to evaluate transitions in species distribution, rooting depth and density, and other characteristics affecting transpiration, and to assess whether transitions are coupled to pedogenesis. The results will be used to identify physical, hydrological, and biological mechanisms that affect cover performance and to provide insight into how covers change over time. The lessons learned will be used to improve cover design and construction and for assessments of long-term performance. The findings will also apply to other hydrologic problems (e.g., natural recharge, urban watershed hydrology, infiltration and runoff in engineered landscapes). Additional broader impacts will be obtained by enhanced student learning via inter-disciplinary and inter-institutional collaboration, development of a hydrology module for a middle school environmental science curriculum, and by recruiting diversity students to the project.