Experimental study of natural convection and cooling capacity of closed crushed-rock layers affected by summer rainfall in cold regions

Abstract

Climate-induced rises in air temperature and humidity on the Qinghai-Tibet Plateau modify the hydrothermal conditions of closed crushed-rock embankments (CRE). This alternation arises from the infiltration of summer rainfall, which is closely correlated with the cooling performance of the crushed-rock layers (CRL). Nevertheless, the cooling performance of the closed CRL during the summer rainfall season remains unexplored. In these present, physical models were employed to examine the convective properties and hydrothermal response processes. The results reveal that summer rainfall greatly diminishes the natural convection intensity within the closed CRL. Conversely, cycle-average temperatures showed an upward trend under these conditions. Moreover, based on fluctuations in the thawing/freezing index, the cooling capacity of the CRL weakens post-summer rainfall, with a maximum decline of 27.3% compared with the initial cycle. Additionally, the humidity in the subsoil layer experiences a stepwise growth followed by a gradual decrease owing to concentrated rainwater percolation. After enduring four rainfall events, the volumetric water content in the subsoil layer presents an upward trajectory. Overall, infiltrated water introduces additional heat, modifying the hydrothermal and convective properties of closed CRE, consequently impairing the cooling efficacy of the CRL.