摘要
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 crushed rock embankment can provide cool energy for the permafrost beneath it and guarantee the stability of permafrost without thawing. The cooling effects of the crushed rock embankment are already seen to be verified by in-situ data. However, the mechanism is still to be explored and the design parameters also need to be optimized. The heat transfer in crushed rock railway embankment could be treated as the air convection problem in porous media. Here, the local thermal equilibrium is assumed to exist between the air and the grains; and the air is expressed by the Boussinesque approximation. The heat transfer equations, the motion equation, and the conservation equation are achieved with finite element formulas of Galerkin's method; and then, a program 3G2003 to simulate the heat transfer in crushed rock embankment is developed. Simulations are performed on the crushed rock roadbeds composed of crushed rock with diameters of 3, 6, 9 and 15 cm, respectively. The results shows that the 9 cm-crushed rock embankment has the best cooling effect, which will cause a decrease of 1.18°C in the temperature at the base of embankment; and air convection occurs in entire interior embankment. The temperature field shows prominent nonlinear characteristics, and the average air speed at the bottom of embankment is 0.73 m/h. The embankment composed of crushed rock of 6 cm in diameter will induce a decrease of 0.78°C in temperature, accompanied by weak air convection with air speed of 0.21 m/h at the base of embankment. The embankments consisting of 3 cm and 15 cm diameter crushed rock have poor cooling effect, which will have 0.21°C and 0.28°C decrease in temperature, respectively, where air speed at the bottom approximate zero. Therefore, the 9 cm diameter crushed rock is recommended for the construction of Qinghai-Tibet railway so that permafrost embankment can be protected.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2005年第11期1947-1953,共7页
Chinese Journal of Rock Mechanics and Engineering
基金
中国科学院知识创新工程重大项目资助项目(KZCX1–SW–04)
关键词
道路工程
碎石路基
多年冻土
多孔介质
青藏铁路
降温效果
Cooling
Equations of motion
Finite element method
Galerkin methods
Grain size and shape
Heat transfer
Optimization
Permafrost
Porous materials
Railroads
Rocks
