Investigation of Physical and Chemical Clogging Phenomena in Underdrain Stormwater Systems Utilizing Geotextiles

在美国和世界各地，拆除材料和建筑废物的产量一直在逐步增加，尽管用于处置的土地越来越有限，而且越来越昂贵。因此，回收的未结合材料的使用已经变得普遍。近年来，在土木工程应用中，从回收破碎混凝土生产的骨料（称为再生混凝土骨料- RCA）的使用大幅增加，以降低生产成本，施工时间，并参与可持续实践。随着使用量的增加，RCA的物理、机械和环境特性已被广泛研究，以支持其在各种岩土工程应用中用作回填或结构填料的适用性。尽管以前的研究，沉淀钙质材料（特别是方解石的沉积）从RCA沥滤液的潜力还没有得到很好的理解。不了解这种行为可能会导致意外后果的基础上不正确的使用，不适当的设计，或不必要的限制，特别是在暗渠雨水系统。例如，当雨水系统采用天然土壤/骨料设计时，主要针对土工织物过滤器的物理堵塞进行评估。然而，对于RCA，单独评估物理堵塞是不够的，因为这种现象是基于细颗粒的迁移，并没有描述从RCA沉淀方解石的可能性。本研究的主要目的是调查和了解的化学现象，导致方解石沉淀和晶体生长的土工织物介质从RCA在类似的条件下暗渠雨水系统。这是一个为期一年的探索性实验研究计划，以检查现有的方解石沉淀速率模型的适用性，理论方解石晶体生长动力学模型在自然沃茨。目的是量化和预测RCA中方解石沉淀的发生。本文将试图回答以下问题：（1）方解石晶体在土工织物上的沉淀;（2）使用PWP机理模型对RCA中方解石沉淀动力学的近似;（3）量化物理和化学堵塞现象之间的差异;（4）基于化学和物理堵塞现象的耦合效应来确定土工织物使用性能的降低程度。这项探索性研究的结果还将确定可能需要进一步，更长时间和更深入调查的复杂性，以便进行后续研究计划。这项研究的结果将产生变革性的知识，（1）理解化学现象，（2）区分与RCA一起建造的土工布的暗渠雨水系统的物理和化学堵塞。

The production of demolition material and construction waste has been increasing at a gradual pace in the United States and around the world, although the land for disposal is becoming limited and more expensive. Consequently, the use of recycled unbound material has become widespread. In recent years, there has been substantial increase in the use of aggregate produced from recycling crushed concrete (referred as recycled concrete aggregate - RCA) in civil engineering applications to reduce production costs, construction time, and engage in sustainable practices. With increased usage, the physical, mechanical, and environmental properties of RCA have been widely investigated to support its suitability for using it as backfill or structural fill in variety of geotechnical applications. Despite previous research, the potential of precipitating calcareous material (in particular, deposition of calcite) from RCA leachate is not well understood. Not understanding this behavior may lead to unintended consequences based on incorrect use, inappropriate design, or unnecessary limitations especially in underdrain stormwater systems. For example, when stormwater systems are designed with natural soils/aggregates, they are primarily evaluated against the physical clogging of the geotextile filter. However with RCA, evaluating the physical clogging alone is not sufficient as this phenomenon is based on migration of fine particles and does not describe the potential of precipitating calcite from RCA. The main objective of this research is to investigate and understand the chemical phenomena leading to calcite precipitation and crystal growth within geotextile media from RCA under conditions similar to underdrain stormwater systems. This is a one-year exploratory experimental research program to examine the suitability of existing calcite precipitation rate models, and theoretical calcite crystal growth kinetics models in natural waters. The objective is to quantify and predict the calcite precipitation occurrence in RCA. An attempt will be made to answer questions regarding (1) precipitation of calcite crystals over geotextile; (2) approximation of the kinetics of calcite precipitation from RCA using the mechanistic PWP model; (3) quantifying the difference between physical and chemical clogging phenomena; and (4) defining the degree in reduction in serviceability of geotextile based on coupling the effects of both chemical and physical clogging phenomena. The findings from this exploratory research will also identify the complexities that may require further, longer, and more in-depth investigation for a follow-up research program. The outcome of this research will yield transformative knowledge in terms of (1) understanding the chemical phenomenon and (2) differentiating between physical and chemical clogging of underdrain stormwater systems with geotextiles constructed alongside RCA.