Numerical Study On Cooling Effect And Mechanism Of New Type Ripraped-Rock Slope

As an effective cooling measure for railway embankment in permafrost soils, cooling effect and mechanism are different in porous media for different particle size of the ripped-stone, embankment height and thickness of ripped-stone layer of the new type ripraped-rock slope. Based on the equations of heat transfer in large porous media and the program 3G2001 developed by Doctor Chen Feixiong and author's advisor, we concentrate our attention on the cooling effect influenced by factors such as embankment height, particle size of the ripped-stone, thickness of ripped-stone layer, air density and soil property of active layer. The following achievements were made:(1) Compared to traditional ripraped-rock slope ,the transfer depth of -2°C temperature wave has increased about 10～20% for newly new type ripraped-rock slope, which is more effective than forced convection caused by strong wind. The transfer depth of -2°C temperature wave in the tenth annual has increased as twice as the first year, Compared to other embankments height, it has showed a better cooling effect. The thawing depth of 4m height in the center section of embankment was the lowest in the last six years while the thawing depth of traditional ripraped-rock slope rised with the increasing of embankment height.(2) The numerical studies has showed that benefiting from awning board, the optimum particle size of the ripped-stone for new type ripraped-rock slope was obtained by resolving the contradiction of traditional ripraped-rock slope 's cooling character. It is most effective when particle size of the ripped-stone is 15cm. And analysis results also showed that air density has little influence on the cooling effect for new type ripraped-rock slope.(3) It was generally considered that the thicker the better. for traditional ripraped-rock slope The numerical simulations conducted in this paper showed that it exists an optimal thickness as a result of the natural convection (different from the forced convection induced by strong wind.)for new type ripraped-rock slope.(4) Soil characters of active layer has a distinct influence on the cooling effect. It has played a role as thermal insulation materials while thermal conductivity is small. So it is difficult to balance the thermal income and expense. The cooling effect was excellent while thermal conductivity is large, but the depth of active layer may be increased at the same time because of its large amplitude of temperature wave.