Experimental study on cooling effect of open crushed-rock layer under the rainfall in summer

The increased rainfall in summer induces warming and humidification of the Qinghai–Tibet Plateau, significantly affecting the temperature boundaries and cooling effects of the crushed-rock embankment (CRE). The crucial issue of quantitatively characterizing the hydrothermal changes and the cooling effects of CRE has not been considered in previous research. Therefore, an experimental study on the open crushed-rock layer (CRL) under rainfall infiltration was conducted. Based on the freezing and thawing indices and heat budget of the underground layer, the influence of summer rainfall on the cooling effect of open CRL was evaluated. The results showed that the periodic average temperature of the underground layer first decreased to negative values and then increased to positive values affected by summer rainfall. The freezing and thawing indices and their ratio gradually decreased. The cooling effect of open CRL was weakened, with a maximum decrease of 15.20%. After summer rainfall, the volumetric water content and heat flux of the underground layer increased sharply and then decreased rapidly, and the maximum increases for the peak values were 28.8% and 88.81 W/m 2 , respectively. The average volumetric water content for each cycle gradually increased and reached saturation. Meanwhile, heat absorption gradually increased, and the heat release of the underground layer first increased and then decreased with the cumulative rainfall. The large amount of latent heat released by the water–ice phase change was a key factor for the degradation of the cooling effect of open CRL.