Advanced thermo-hydro-mechanical interactions in underground structures

该项目旨在描述地下结构的不同组成部分与周围土壤之间的热-水-机械相互作用的影响，以及对其设计的后续影响。使用二维和三维有限元模型的组合探索了温度变化的两个来源：使用热交换器管道的结构的激活和混凝土的水化。对于前者，本项目将在前人对挡土墙、桩基等热活结构简化建模工作的基础上，通过显式模拟换热器管道，分析热负荷建模对跨桩段温度场的影响。这也将使我们能够首次对这些结构中的热通量进行分析，展示在不同的时间框架内热量被储存在哪里，并描述这种储存的效率，进一步表明这些系统作为建筑低碳供暖和制冷供应商的能力。最后，预计将有一种简化而准确的建模方法，可以在不需要昂贵的计算3D有限元分析的情况下产生由于温度变化引起的桩力估计，从而使其设计更易于行业从业者使用。第二个要考虑的热源是混凝土的水化作用。这些结构的特点是在地面上挖出的洞中倒入大量的混凝土。随后的化学反应是极度放热的，产生大量的热量，从结构流到地下，触发一个复杂的相互作用机制，该项目将分析。本文将建立一个新的实用模型，用于模拟岩土有限元分析中的这一过程，并将其实现到定制代码ICFEP中。将对地下结构周围的温度场进行表征，并在可能的情况下，将结果与现场数据进行比较以进行验证（例如，热完整性测试的温度场）。最后，将研究水化过程中产生的温度场对热活性结构安全运行的影响。

This project aims at characterising the effect of thermo-hydro-mechanical interactions between different components of underground structures and the surrounding soil, and the subsequent impact on their design. Two sources of temperature changes are explored using a combination of 2D and 3D finite element modelling: the activation of structures using heat exchanger pipes and the hydration of concrete. Concerning the former, building upon work carried out by researchers on simplified modelling of thermo-active structures, such as retaining walls and pile foundations, this project will analyse the impact on the temperature fields across the pile section of modelling the thermal loading by explicitly simulating heat exchanger pipes. This will also enable a first-of-its-kind analysis of thermal fluxes in these structures, demonstrating where heat is being stored in different time-frames, as well as characterising the efficiency of such storage, providing further indication of these systems' capabilities as a providers of low-carbon heating and cooling to buildings. Lastly, it is expected that a simplified, yet accurate, modelling approach that yields estimates of pile forces due to temperature changes without the need for computational expensive 3D finite element analysis is produced in order to render their design more approachable by industry practitioners. The second heat source to be considered is the hydration of concrete. These structures are characterised by very large quantities of concrete poured into excavated cavities within the ground. Subsequent chemical reactions are extremely exothermic, producing large quantities of heat that flows from the structure into the ground, triggering a complex interaction mechanism which this project will analyse. A new practical model for simulating this process in geotechnical finite element analyses will be formulated and implemented into the bespoke code ICFEP. Temperature fields around underground structures will be characterised and, where possible, results will be compared to field data for validation purposes (e.g. temperature fields from thermal integrity testing). Lastly, implications from temperature fields generated during hydration to the safe operation of thermo-active structures will be investigated.