Unsaturated Hydraulic Characterization of Expansive Clays

膨胀粘土的不饱和水力表征

• 批准号: 1335456
• 负责人: Jorge Zornberg
• 金额: $ 34.13万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1335456&HistoricalAwards=false
• 关键词: Unsaturated; Hydraulic; Characterization; Expansive; Clays

The overall objective of this research is to experimentally determine the unsaturated hydraulic properties of expansive clays while, at the same time, gain insight into the relationships between these hydraulic characteristics and the magnitude of swelling. Accounting for the soil volumetric strains as an additional variable within the framework of unsaturated hydraulic characteristics adds complexity to the already intricate, non-linear relationships representing the response of volumetric water content and hydraulic conductivity as a function of the soil matric suction. This investigation will use centrifuge technology to allow measurement of the unsaturated hydraulic characteristics and associated volumetric changes in expansive clays. Specifically, centrifuge testing will be used for the continuous and expeditious measurement of the changing soil moisture content, suction, hydraulic conductivity and void ratio that occur during unsaturated flow. This study will allow: (i) gaining insight into the relationships between unsaturated hydraulic properties and volume changes in highly plastic clays, (ii) expeditiously determining the hydraulic properties of highly plastic clays, (iii) understanding the boundary conditions and stresses in clay specimens subjected to open flow centrifugation, (iv) quantifying the effect of normal stress, initial moisture content, initial void ratio, soil fabric and imposed inflow rate on the magnitude and rate of swelling, and (v) developing models that are suitable to represent the soil water retention curve, the hydraulic conductivity function, and the swell-stress relationship of expansive clays.Because of conceptual and experimental complexities, the characterization of unsaturated hydraulic properties of expansive clays has remained largely unexplored. Yet, significant benefits will result from gaining insight into the variables governing the unsaturated flow in expansive clays, as the annual cost of damages in the US induced by moisture fluctuations in expansive soils has been reported to exceed that caused by floods, hurricanes, earthquakes and tornadoes combined. The broader impacts resulting from the proposed activity include: (i) using centrifuge testing not only for geotechnical modeling but also for hydraulic characterization of expansive clays, (ii) increasing community awareness of the problems associated with the presence of expansive clays, (iii) transferring of fundamental findings from this research into practical recommendations, and (iv) developing educational modules that are useful to integrate research into geotechnical instruction as well as to introduce geo-hazards concepts into outreach minority programs.

本研究的总体目标是通过实验确定膨胀粘土的不饱和水力特性，同时深入了解这些水力特性与膨胀程度之间的关系。 将土壤体积应变作为不饱和水力特性框架内的附加变量，增加了已经复杂的非线性关系的复杂性，该非线性关系表示体积含水量和导水率作为土壤基质吸力的函数的响应。 这项研究将使用离心机技术来测量膨胀粘土的不饱和水力特性和相关的体积变化。 具体来说，离心机测试将用于连续、快速测量非饱和流动过程中发生的土壤含水量、吸力、导水率和空隙率的变化。 这项研究将允许：(i) 深入了解高塑性粘土的不饱和水力特性和体积变化之间的关系，(ii) 迅速确定高塑性粘土的水力特性，(iii) 了解粘土样本中的边界条件和应力进行开流离心，(iv) 量化法向应力、初始含水量、初始空隙率、土壤结构和施加的流入速率对膨胀幅度和速率的影响，以及 (v) 开发适合代表土壤保水曲线、导水率函数以及膨胀粘土的膨胀-应力关系。由于概念和实验的复杂性，膨胀粘土的不饱和水力特性的表征在很大程度上仍未得到探索。 然而，深入了解控制膨胀粘土不饱和流动的变量将带来显着的好处，因为据报道，在美国，膨胀土湿度波动造成的每年损失成本超过了洪水、飓风、地震和自然灾害造成的损失。龙卷风合并。 拟议活动产生的更广泛影响包括：（i）使用离心机测试不仅用于岩土工程建模，还用于膨胀粘土的水力表征，（ii）提高社区对与膨胀粘土的存在相关的问题的认识，（iii）将这项研究的基本发现转化为实际建议，以及（iv）开发有助于将研究融入岩土工程教学以及将地质灾害概念引入到少数群体外展计划中的教育模块。