Accumulative effect of cooling capability in air-tight crushed rock layer with horizontally embedded perforated ventilation pipes

A crushed rock layer of highway embankment with a horizontally embedded perforated ventilation pipe is employed in warm permafrost regions of the Qinghai-Tibet Plateau. Laboratory experiments on the cooling capability in the air-tight crushed rock sample with a horizontally embedded perforated ventilation pipe are performed. The accumulative effect of cooling capability is analyzed. The analysis shows that the air-tight crushed rock embankment with a perforated ventilation pipe can enhance the forced convective cooling capability of the embankment base due to pore air motion in the crushed rock region near the ventilation pipe forming a pore air circulation in conjunction with the ambient cold air through the small holes in pipe wall, and improve the natural convection cooling capability due to pore air circulation occurring in the upper crushed rock region during the negative air temperature ventilating period. The temperatures in the lower crushed rock region quickly tend to negative values with the increase of air temperature fluctuating cycles. This accumulative effect of cooling capability may ensure the thermal stability of highway embankment in warm permafrost regions.