高温冻土区新型复合护坡降温机制研究

Cooling effects and mechanisms of crushed rock protective slopes combined with shading board on embankment in warm permafrost regions

遮阳板碎石复合护坡是一种集碎石护坡和遮阳板护坡双重效用于一体的新型复合护坡结构,是一种很好的治理高温冻土区块碎石护坡路基病害的补强措施。基于遮阳板和块碎石单个工程措施降温机制的研究,通过对这种新型复合护坡路基的温度场和速度场特征以及降温过程的研究,提出新型复合护坡路基的降温机制。研究发现,封闭新型复合护坡的主要降温机制是:复合护坡中遮阳板有遮阳和挡风雪作用,碎石层有"热半导体"效应和"热屏蔽效应"(屏蔽遮阳板的二次辐射);开放新型复合护坡的主要降温机制是:遮阳板有遮阳、挡风雪作用,碎石护坡有"热屏蔽效应"(屏蔽热风和二次辐射)和"烟囱效应",遮阳板和碎石护坡组合的通道有"虹吸效应"、"狭管效应"和"烟囱效应"。研究成果完善和深化了新型复合护坡路基研究基础,而且对遮阳板和块碎石结构在青藏铁路或青藏公路中的应用提供科学依据和技术支撑。

On the basis of in situ measurements, it is necessary that the embankment only with crushed rock protective slopes in the warm permafrost regions along the Qinghai-Tibet Railway needs proactive mitigative measures to maintain the long-term stability. Thus, an ad hoc technique of the crushed-rock protective slopes and the awning combination （CPS-AC） was proposed. The cooling effect and mechanisms of the CPS-AC were explored on the basis of previous studies on the individual mitigative measures of the awning and the crushed-rock protective slopes, and of the current studies on the temperatures and velocities of the CPS-AC embankment configurations. The CPS-AC is further divided into two types, the closed and open systems. In the closed system, the airs between in the ambient environment and under the awning can not exchange freely. In reverse, the airs can do freely in the open system. The awning in the closed CPS-AC can shade the direct solar radiation on the protective slopes and protect the embankments from blowing sands and snow, as well as winds; and the crushed rock layer in the closed CPS-AC has the ＂thermal semi-conductor＂ effect and can shade the secondary radiation from warm awning. In the open CPS-AC system, the shading board shades sunlight and obstructs snow, and the crushed rock layer can shield the secondary radiation of the warmer awning, and protect warmer winds from entering the embankment, and also has a chimney effect for cooling the embankment. The cooling effect of the open channel between the awning and the crushed rock slope can be explained using the siphon, channeling and chimney cooling effects. The measurements and research on the effects and mechanisms have provided important evidences and application techniques for the CPS-AC practices in the Qinghai-Tibet Railway.