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行为的影响涉及到各种岩土工程问题，如埋地高压电缆技术、浅孔或深孔地热能源生产或石油和天然气生产。此外，热和水力方面在乏燃料和中水平核废料贮存库的概念设计中也非常重要。另一方面，由于气候变化，预计世界范围内，甚至中欧和北欧地区的自然土壤将出现热干燥。上述情况所涉及的典型土壤通常具有膨胀性。然而，膨胀材料热-水-力耦合特性的实验研究存在着严重的困难，并且在岩土工程实验室中还不是一种惯常的做法。由于这个原因，缺乏常规的实验室技术来表征膨胀土的THM行为，如果有任何实验程序可用，他们通常只处理饱和条件下的土壤调查。非饱和thm材料表征的实验数据有限，特别是膨胀粘土的实验数据。因此，本文提出的主要目的是通过设计一个实验程序来产生热和水力梯度下膨胀土的温度、吸力和含水量剖面，从而填补这一空白。虽然实验工作在研究土壤中THM过程中起着重要作用，但由于实验室测试特别是膨胀材料的实验室测试通常非常耗时和昂贵，因此可能无法自给自足。因此，在本项目中，我们建议开发和实施理论和数值模拟概念，用于预测特定thm实验期间的土壤行为，以及在显著延长实验室测试持续时间的一段时间内持续进行预测。为了使本研究完成，进一步的目标是通过反分析校准数值模型和所采用的物质定律，并通过模型敏感性分析验证结果。

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.