Considering Thermal Conductivity of Injection Solutions in Combination with Cooling Systems Within the Railway Formation Foundation

Under specific conditions, the degradation of the permafrost soils in railway formation foundations is not only characterized by thermal subsidence, but also by the development of weak soils that consolidate over time, potentially leading to slope instability and embankment creep. In such scenarios, a combined thermal stabilization approach can be applied, which includes the injection of soil-cement solutions alongside the installation of vapour-liquid cooling systems (SCD). This research establishes the correlation between the thermal conductivity coefficients of hardened injection solutions and the binder content. It also conducts a numerical model of the thermal stabilization of a soil mass to assess the effectiveness of the combined method, measured by the heat transfer coefficient, in comparison with the application of vapour-liquid systems alone. Methods: A laboratory experiment was set up and carried out to determine the thermal conductivity coefficient of solutions using the steady-state thermal regime method. Heat engineering calculations were performed using a specialized software package. Results: The dependences of the thermal conductivity coefficients of hardened soil-cement injection mortars on the binder content have been determined under various conditions, such as air-dry state, full water saturation, and frozen-thawed states. It has been established that the thermal conductivity of the hardened mortar is significantly greater than that of the original soil in equivalent conditions, with a notable relative impact observed even at minimal binder content. Practical significance: The established relationships are recommended for addressing practical challenges associated with injecting soil-cement mortars into the foundations of transportation structures in areas where permafrost soils are prevalent. Numerical modelling has demonstrated that the combined method proposed for thermal stabilization of the soil mass is more effective in terms of heat exchange coefficient than relying solely on vapour-liquid soil-cement mixtures, highlighting the importance of this consideration in design and calculations.