Experimental investigation on influence of grain-diameter on cooling effect of crushed rock revetment with permeable boundary

A series of experiments were constructed for the cooling effect of crushed rock revetments with different grain diameters under permeable boundary condition.The grain-diameters of crushed rock included four kinds: 6～8,14～16,21～ 23,28～30 cm.The experimental results indicated that,under the windward and leeward conditions,the cooling effect of crushed rock revetments with all these four grain-diameters was good and could effectively reduce the temperatures of the underlying soil layers;furthermore,the mean periodic temperatures of soil slope surfaces under crushed rock revetments could be lowered down below 0 ℃ after two experimental cycles.Under windward condition,with the increase of grain diameter,the cooling effect of crushed rock revetment became better when its grain diameter ranged between 6 and 30 cm;under leeward condition,the cooling effect of crushed rock revetment with a grain diameter range of 21～23 cm was best.Besides,It was found that,under the experimental condition,the periodic temperature at the bottom of crushed rock revetment was mainly dominated by windward/leeward condition,and not by grain-diameter of crushed rock.Namely,the periodic temperature at the bottom of windward crushed rock revetment was far larger than that at leeward one,and the positive temperature range at the bottom of crushed rock revetment under windward condition in every cycle was far higher than that under leeward condition.Furthermore,the duration of the positive temperature was longer under windward condition.Therefore,it would be disadvantageous to the stability of permafrost embankment.