透壁式通风管–块石复合路基降温效果模型试验及数值模拟

Model test and numerical simulation of cooling effect of ventilated duct-crashed rock composite embankment

为研究透壁式通风管–块石复合气冷路基的降温效果,针对年均气温-3.5℃,平均风速2.5 m/s,主导风向为西北方向的高原环境条件开展了室内模型试验,对比分析了单一块石路基和透壁式通风管–块石复合路基的孔隙空气对流速度、特征点地温及模型整体温度场变化过程。试验结果表明:在透壁式通风管的疏导作用下,通风管与块石层复合结构能够起到强化路基体对流的效果,复合路基块石孔隙中的空气流速比单一块石路基提高约20%,使得复合路基模型底部的降温幅度是单一块石路基模型的2.2倍。建立了透壁式通风管–块石复合路基数值计算模型,对通风管内空气流速分布、路基温度场变化进行了预测分析。结果表明:空气流速在通风管中心达到最大值4.06 m/s,在管壁处流速出现跃变陡降,在块石介质区域里速度的数量级为10-1,与室内试验的结果较为一致。模型试验和数值计算结果均表明复合路基能够起到储存冷量、降低下伏多年冻土地温的作用。

In order to study the cooling effect of ventilated duct-crashed rock composite embankment, a series of model tests are carried out under plateau environment conditions. The average annual temperature is-3.5℃, the average wind speed is 2.5 m/s, and the dominant wind direction is northwest. The air convection velocity in crashed rock, the change process of temperature at feature points and the temperature field of model are analyzed. The results indicate that an enhanced convection effect in embankment can be generated by the ventilated duct-crashed rock composite embankment. Under the effect of grooming by the ventilated duct, the air convection velocity in the composite embankment is 20% higher than that in a single crashed rock embankment, and the cooling rate at the bottom of the model of the composite embankment is 2.2 times that of the single crashed rock embankment. A numerical model for the ventilated duct-crashed rock composite embankment is established. The velocity distribution in the ventilated duct-embankment temperature field is analyzed. Numerical calculations show that the air flow rate which reaches a maximum at the center vent pipe is 4.06 m/s. A rapid decline in velocity occurs at the wall of the ventilated duct. The magnitude of the air flow in the crashed rock is 10-1. The calculated results are consistent with those of laboratory tests. The model test and numerical simulaton show that the composite embankments can deposit cold quantity and cool down the permafrost.