Transient water transport in expansive soils under coupled hydraulic, mechanical and thermal boundary conditions: Experimental and numerical study

热湿耦合流动及其对土壤性质的影响涉及到各种岩土工程问题，如埋地高压电缆技术、浅井或深井地热能生产或石油和天然气生产。此外，热力和水力方面在乏核燃料和中级核废料储存库的概念设计中非常重要。另一方面，由于气候变化，预计世界范围内甚至在中欧和北欧地区都会出现自然土壤的热干化。上述情况涉及的典型土壤往往是膨胀性的。然而，膨胀材料的热-水-力(THM)耦合特性的实验研究存在着严重的困难，而且在岩土实验室中并不是习惯性的做法。由于这个原因，膨胀土特性的THM表征缺乏常规的实验室技术，如果有任何实验程序可用，它们通常只在饱和条件下进行土壤调查。关于不饱和THM材料特性的实验数据是有限的，特别是在膨胀粘土的情况下。因此，这项研究的主要目的是通过设计一种实验程序，在温度和水力梯度下产生膨胀土内的温度、吸力和水分分布，从而为填补这一空白做出贡献。虽然实验工作在研究土壤中的THM过程中起着重要的作用，但它可能不是自给自足的，因为实验室测试，特别是对膨胀材料的测试，通常非常耗时和昂贵。因此，在这个项目中，我们建议开发和实施理论和数值模拟概念，用于在特定的THM实验期间以及在显著延长实验室测试持续时间的时期内预测土壤行为。为了完成这项研究，本文的进一步目标是通过反分析对数值模型和所采用的材料定律进行校正，并通过模型灵敏度分析对结果进行验证。

Coupled thermal and moisture flows and their consequences on soil behavior are involved in a variety of geotechnical problems such as buried high voltage power cable technology, geothermal energy production from shallow or deep boreholes or oil and gas production. Moreover, thermal and hydraulic aspects are of great importance in the conceptual design of repositories for spent nuclear fuel and medium level nuclear waste. On the other hand, as a consequence of climate change, thermal desiccation of natural soils is expected worldwide and even in areas of central and northern Europe. The typical soils involved in the above mentioned situations often are of expansive nature. However, the experimental study of the coupled thermo-hydro-mechanical (THM) behavior of expansive materials possesses serious difficulties, and it is not a habitual practice in geotechnical laboratories. For this reason, there is a lack of conventional laboratory techniques for THM characterization of expansive soil behavior, and if any experimental procedures are available they usually address soil investigation only under saturated conditions. Experimental data regarding unsaturated THM-material characterization are limited, especially in case of expansive clays. Hence the major aim of the proposed here investigation is to contribute in filling the gap by means of designing an experimental procedure to generate temperature, suction and water content profiles within the expansive soil under thermal and hydraulic gradients. Although experimental work plays an important role in studying the THM processes in soils it may not be self-sufficient because the laboratory tests especially for expansive materials are usually highly time consuming and costly. Therefore, in this project we propose to develop and implement theoretical and numerical modeling concepts for prediction of soil behavior during a particular THM-experiment as well as continuously in a period significantly extending the laboratory test duration. In order to make this study complete the further objectives addressed here are the calibration of the numerical model and the employed material laws via back analysis and the validation of the results by means of model sensitivity analysis.