Predictive modelling of thermo-active tunnels in London Clay

Abstract

Thermo-active structures are underground facilities which enable the exchange of thermal energy between the ground and the overlying buildings, thus providing renewable means of space heating and cooling. Although this technology is becoming increasingly popular, the behaviour of geotechnical structures under additional thermal loading is still not fully understood. This paper focuses on the use of underground tunnels as thermo-active structures and explains their behaviour through a series of finite element analyses based on an existing case study of isothermal tunnels in London Clay. The bespoke finite element code ICFEP is adopted which is capable of simulating the fully coupled thermohydro-mechanical behaviour of porous materials. The complex coupled interactions between the tunnel and the surrounding soil are explored by comparing results from selected types of coupled and uncoupled simulations. It is demonstrated that: (1) the thermally-induced deformation of the tunnel and the ground are more critical design aspects than the thermally-induced forces in the tunnel lining, and(2) the modelling approach in terms of the type of analysis, as well as the assumed permeability of the tunnel lining, have a significant effect on the computed tunnel response and, hence, must be chosen carefully.

Multiphysics coupling in exploitation and utilization of geo-energy: State-of-the-art and future perspectives

“…Energy piles have received the most attention during the past two decades, and laboratory testing, field monitoring and numerical modelling have been carried out (Song et al, 2022;Cui et al, 2023). Some other types of energy geostructure (e.g., energy tunnels and walls) have only garnered significant interest recently (Peltier et al, 2019;McCartney et al, 2020;Gawecka et al, 2021;Liu and Zhou, 2022).…”

An unconstrained stress updating algorithm with the line search method for elastoplastic soil models

“…Tunnel excavation simulation is a typical application for the MCC model in the numerical analysis of geotechnical engineering (Gawecka et al 2021). This subsection considers a numerical example of tunnel excavation with lining support.…”

Thermo-mechanical analysis of energy tunnels accounting for thermo-plasticity

“…This innovative technology offers renewable methods of space heating, cooling and hot water production. While still relatively uncommon, it is becoming increasingly popular due to the growing interest in sustainability and innovation, particularly in large infrastructure projects [8,7,10]. Additionally, the increasing need for clean and renewable sources of energy has made energy tunnels an attractive solution for addressing the global climate challenge [7,11,1].…”

“…The proposed model is validated following several steps. First, the mechanical model is calibrated against field data from tunnels constructed in soft soils [10]. Then, thermo-mechanical effects are validated using existing monitoring data from real-scale tunnels available in literature [3,4,10,14].…”

“…First, the mechanical model is calibrated against field data from tunnels constructed in soft soils [10]. Then, thermo-mechanical effects are validated using existing monitoring data from real-scale tunnels available in literature [3,4,10,14]. For further validation, model estimations are compared with results from small-scale thermalmechanical tests, such as thermal-triaxial tests.…”