Thermal influence zone of energy tunnels in sandy soils under the hydrostatic condition

IF 3.7 2区工程技术 Q3 ENERGY & FUELS

Geomechanics for Energy and the Environment Pub Date : 2025-09-01 Epub Date: 2025-07-13 DOI:10.1016/j.gete.2025.100716

Alaaeldin Magdy , Alice Di Donna , Hussein Mroueh

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Abstract

Energy geostructures are more and more considered as a possible solution to cover heating and cooling needs. They function according to the principle of shallow geothermal energy, exchanging heat with the ground. This results in a zone underground where the temperature of the ground is affected by the presence of the geothermal system, which is called thermal influence zone. As the number of energy geostructures increases, determining their thermal influence zone becomes crucial, especially in environments where adjacent energy geostructures or other geothermal systems coexist. Indeed, avoid or minimize the overlap between the thermal influence zones of different geothermal installations is important to ensure their efficiency. This study investigates the effects of groundwater level, thermal operation period, and ground permeability, in both heating and cooling modes, on the thermal influence zone generated around an energy tunnel. The results indicate that the thermal induced change in groundwater density and viscosity due to geothermal operations generates groundwater circular flows. These flows play a major role in shaping the thermal influence zone. In the heating mode (winter), when the groundwater is within the vicinity of the tunnel, i.e., above, at or just below the tunnel, the thermal influence zone takes an oval shape elongated below the tunnel invert. In the cooling mode (summer), the thermal influence zone does not follow a specific shape, and it is remarkably changed by the groundwater level. For instance, when the groundwater level is shallow, the thermal influence zone extends significantly upward, potentially overlapping with the surface layer affected by atmospheric air temperature. However, when the groundwater level at the tunnel centreline, the thermal influence zone takes a horizontal oval shape, which might interfere with adjacent similar installations. The expansion of the thermal influence zone is highly dependent on the operation duration. In winter, the downward elongation after 6 months operation reaches around 1.5 times that after 3 months.

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静水条件下砂土能量隧道热影响区

能源土工结构越来越被认为是满足供暖和制冷需求的可能解决方案。它们根据浅层地热能原理工作，与地面交换热量。这就产生了地下的一个区域，在这个区域里，地面的温度受到地热系统的影响，这个区域被称为热影响区。随着能源土工结构数量的增加，确定其热影响区变得至关重要，特别是在邻近能源土工结构或其他地热系统共存的环境中。事实上，避免或尽量减少不同地热装置的热影响区之间的重叠对于确保其效率非常重要。研究了地下水位、热力运行周期和地下渗透率对能量隧道周边热影响区的影响。结果表明，地热开采引起的地下水密度和粘度的热致变化产生了地下水循环流动。这些气流在形成热影响区方面起主要作用。在采暖模式下（冬季），当地下水处于隧道附近，即隧道上方、下方或下方时，热影响区在隧道仰拱下方呈椭圆形拉长。在降温模式下（夏季），热影响区不遵循特定的形状，受地下水位的影响变化显著。例如，当地下水位较浅时，热影响区明显向上延伸，可能与受大气温度影响的表层重叠。然而，当地下水位在隧道中心线时，热影响区呈水平椭圆形，可能会干扰邻近的类似设施。热影响区的扩展高度依赖于运行时间。冬季手术6个月后的下伸率达到3个月后的1.5倍左右。

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来源期刊

Geomechanics for Energy and the Environment Earth and Planetary Sciences-Geotechnical Engineering and Engineering Geology

CiteScore

5.90

自引率

11.80%

发文量

期刊介绍： The aim of the Journal is to publish research results of the highest quality and of lasting importance on the subject of geomechanics, with the focus on applications to geological energy production and storage, and the interaction of soils and rocks with the natural and engineered environment. Special attention is given to concepts and developments of new energy geotechnologies that comprise intrinsic mechanisms protecting the environment against a potential engineering induced damage, hence warranting sustainable usage of energy resources. The scope of the journal is broad, including fundamental concepts in geomechanics and mechanics of porous media, the experiments and analysis of novel phenomena and applications. Of special interest are issues resulting from coupling of particular physics, chemistry and biology of external forcings, as well as of pore fluid/gas and minerals to the solid mechanics of the medium skeleton and pore fluid mechanics. The multi-scale and inter-scale interactions between the phenomena and the behavior representations are also of particular interest. Contributions to general theoretical approach to these issues, but of potential reference to geomechanics in its context of energy and the environment are also most welcome.