Numerical simulation of the anti-freezing performance of a phase change clay core-wall with loose covering

Abstract

Clay core-wall of rockfill dam may endure short-term freezing or freeze–thaw cycles owing to negative temperature conditions during winter construction in cold regions, resulting in the degradation of the clay compaction, frost swelling, and cracking performance. The most commonly used insulation cover measures interfere with the continuous construction of clay core-walls, which may shorten the effective time available for construction and delay the dam construction progress. To address this problem, we proposed using the upper layer of the loose-covering clay and the latent heat of phase change materials (PCMs) to control the core-wall temperature. We implemented a numerical model for simulating the anti-freezing performance of the PCM mixed clay (PCM-clay) with loose covering. First, a heat transfer model was established using the finite element software COMSOL, and the effectiveness of the model was verified by comparing it with indoor temperature control test results. Subsequently, numerical models including different construction conditions were established, and the temperature control effect was analyzed under different loose-covering thicknesses, initial soil temperatures, and PCM contents. The results showed that at the design ambient temperature and a 2% PCM content, an effective construction time availability of two consecutive days was maintained under a 20-cm-thick loose covering. In contrast, under the same temperature conditions, but for a 4% PCM content, the effective construction time available under a 5-cm-thick loose covering was 43.1 h. Thus, the use of PCM-clay combined with the upper layer loose covering for temperature control proved feasible and effective. Additionally, by increasing the thickness of the loose covering and the initial temperature of the PCM-clay, the PCM content can be reduced. This provides a theoretical basis and a potential technical solution to maximize the time available for construction and accelerate the construction progress of core-wall rockfill dams.