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冻土地区铁路碎石路基内的换热问题可以看成是多孔介质中的对流传导问题。本文假设碎石与路基内部的空气处于热平衡状态,且Boussinesque假定成立。依据多孔介质的质量守恒方程、能量方程及动量方程,并用有限元法离散,建立了碎石路基的数值模型。利用该模型对目前碎石路基设计所关心的几种主要粒径的降温效果进行了数值模拟。结果表明:9cm粒径的碎石路基降温效果最好,空气对流在整个碎石层内发生,碎石层上部温度场呈现非线性特征,路基底部的降温幅度可达1.18℃,空气流速为0.73m/h;而6cm粒径的降温效果次之,路基底部降温0.78℃,空气流速为0.21m/h;3cm与15cm粒径的降温效果较差,对流基本上在路基上部发生,路基底部的对流很弱,降温幅度分别为0.21℃和0.28℃,空气流速接近于0。初步的研究表明,9cm粒径的碎石在碎石路基设计中可优先采用。
The heat transfer problem in the rubble subgrade of the permafrost region can be regarded as the convective conduction problem in porous media. This paper assumes that the gravel and air inside the embankment are in thermal equilibrium and the Boussinesque assumption holds. According to the mass conservation equation, energy equation and momentum equation of porous media, the numerical model of rock subgrade is established by finite element method. The model was used to numerically simulate the cooling effect of several major particle sizes that are currently of interest in gravel subgrade design. The results show that the 9cm diameter crushed stone embankment has the best cooling effect and the air convection occurs in the whole crushed stone layer. The temperature field above the crushed stone layer presents a nonlinear characteristic. The temperature drop at the base of the embankment reaches 1.18 ℃ and the air velocity is 0.73 m / h; and 6cm particle size cooling effect, followed by subgrade cooling 0.78 ℃, the air flow rate of 0.21m / h; 3cm and 15cm particle size cooling effect is poor, convection basically occurred in the upper part of the roadbed, Convection is very weak, the cooling rate of 0.21 ℃ and 0.28 ℃, the air velocity close to zero. Preliminary studies have shown that 9cm particle size gravel can be used preferentially in gravel embankment design.