Advanced thermo-hydro-mechanical interactions in underground structures

该项目旨在表征地下结构的不同组成部分与周围土壤之间的热-水-力相互作用的影响，以及随后对其设计的影响。结合二维和三维有限元模拟，探讨了温度变化的两个来源：利用热交换器管道激活结构和混凝土的水化。关于前者，本项目将在研究人员对挡土墙和桩基等热敏结构简化建模工作的基础上，通过显式模拟换热管来分析建模热负荷对桩截面温度场的影响。这也将使首次能够对这些结构中的热通量进行分析，显示在不同时间范围内热量储存的位置，以及表征这种储存的效率，进一步表明这些系统作为建筑物低碳供暖和冷却的供应者的能力。最后，预计将产生一种简化而准确的建模方法，从而在不需要计算昂贵的3D有限元分析的情况下估计由于温度变化而产生的桩力，以便使其设计更容易被行业从业者所接受。第二个要考虑的热源是混凝土的水化。这些结构的特点是将大量混凝土浇注到地下挖掘的洞穴中。随后的化学反应是非常放热的，产生大量从结构流入地下的热量，触发了一个复杂的相互作用机制，本项目将对此进行分析。在岩土有限元分析中建立了一种新的模拟这一过程的实用模型，并将其应用到定制的程序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.