边坡虹吸排水管内空气积累原因及应对措施

坡体地下水位上升是诱发滑坡的重要因素，实时排出地下水是防治边坡地质灾害的有效手段。虹吸排水具有免动力和流动过程由液位变化自动控制的物理特性，可满足实时排出坡体地下水的需要,但虹吸管中空气积累会导致虹吸过程中断，制约了边坡虹吸排水技术的推广应用。溶解于水的空气因虹吸管内压力降低而释出是形成气泡的物理基础。实验结果表明，虹吸进水口水面以上垂直高度3.5 m以上就会出现大量气泡，经过虹吸顶点后，气泡发生强烈的兼并形成大气泡。当虹吸管的进出水口的水头差较大时，气泡间的水弹容易推动气泡从出水口排出。当虹吸管直径大于5 mm时，缓慢的虹吸流动，会发生管内气泡的积累，最终破坏虹吸过程；虹吸管的直径小于4 mm时，可以形成基本稳定的弹状流。因此，为保持边坡虹吸过程长期有效，经常性降雨并且坡体地下水丰富的地区可选用直径为5 mm的虹吸管，非经常性降雨的地区应选择小于等于4 mm的虹吸管。

Pipe Air Accumulation Causes and Its Control Metod in Slope Siphon Drainage

Rising slope underground water level is an important factor inducing landslide, real-time discharge groundwater is an effective means to prevent the slope geological disaster. The siphon drainage with no power and flowing process by the change of the liquid level automatic control of the physical properties, which can meet the real time need of slope groundwater discharge. But the straw air accumulation leads to siphon destruction, and restricts slope of siphon drainage technology popularization and application. The air dissolved in the water due to the reduced pressure within the siphon overflow is the physical basis of the bubble forming. The experimental results show that, the siphon water inlet above the water surface of the vertical height of 3.5 m above will appear a large number of bubbles, through siphon vertex, bubble generation strongly merger into large bubbles. When the rainbow straw inlet head difference is bigger, bubble water bomb easily push the air bubbles are discharged from the water outlet. When the rainbow straw diameter is greater than 5 mm, slow siphon flow, occurs within the tube bubble accumulation, eventually destroying the siphon process, rainbow straw with diameter less than 4 mm, can form stable slug flow. Therefore, in order to keep the slope siphon process effective long-term, the rainbow straw can be chosen 5 mm in diameter in regular rainfall and slope ungroundwater rich area and less than or equal to 4 mm in diameter in non recurring rainfall area.