The conservation of subterranean cultural heritage sites, particularly those located in karst environments, presents significant challenges due to the complexity of coupled thermal and geological processes. This study addresses the thermal behavior of Lascaux Cave (France), a UNESCO World Heritage site, by developing a 3D heterogeneous thermal model of the surrounding rock mass. The cave is approximately 235 m long, with up to 30 m of overlying rock mass. A geological partitioning was performed using electrical resistivity tomography (ERT) data and machine learning, allowing the rock mass volume to be divided into distinct clusters with homogeneous physical property. An inverse modeling framework, based on the Nelder–Mead simplex algorithm, was employed to estimate the optimal thermal diffusivity of each cluster. An objective function incorporating both phase shift and amplitude damping of periodic thermal signals was introduced to reduce sensitivity to uncertainties in initial temperature conditions. The results demonstrate that heterogeneity in thermal properties significantly influences the spatial distribution of temperatures and improves the accuracy of model predictions compared to conventional homogeneous approaches. This modeling approach provides valuable insight into the cave's thermal regime and establishes a foundation for predicting key conservation-related processes, such as natural convection, condensation, and localized degradation. Future work will focus on integrating the influence of water content and hydrological variations on heat transfer in the rock mass.
The thermal response of lithium-ion batteries subjected to mechanical abuse during active discharge remains insufficiently characterized. In this work, nail penetration experiments were conducted on 25 Ah prismatic LiFePO4 cells while the cells were under 1C discharge at 100%, 90%, 50%, and 20% SOC, with simultaneous localized internal and multi-surface temperature measurements. The embedded thermocouple recorded a localized peak temperature of 909 °C at the specified junction near the penetration region, whereas the maximum surface temperature at the same SOC was 226.0 °C, highlighting a pronounced internal-to-surface thermal gradient. Across the investigated SOC conditions, the maximum surface temperature decreased from 226.0 °C at 100% SOC to 181.7 °C, 95.5 °C, and 91.8 °C at 90%, 50%, and 20% SOC, respectively. The characteristic interval from the onset of rapid surface-temperature rise to the surface-temperature peak was 267.9 s, 312.1 s, 115.9 s, and 152.8 s, respectively, showing a non-monotonic variation among the tested conditions. Although the 50% and 20% SOC cases exhibited comparable peak surface temperatures (95.5 °C and 91.8 °C), obvious vent activation was observed only at 50% SOC, indicating that surface temperature alone is insufficient to explain the observed venting behavior. The results characterize the internal and surface thermal responses of LFP cells subjected to nail penetration during active discharge. Because each SOC condition was represented by a single test, the SOC-dependent differences are interpreted as observations under the present test conditions rather than statistically established trends.
