空气溶入与扩散对高扬程虹吸管内空气积累影响(英文)

Air accumulation in high-lift siphon hoses under the influence of air dissolution and diffusion

目的:探索长时间停流情况下高扬程虹吸管中空气累积现象的发生发展及其对虹吸持续工作的危害,并给出应对该现象的工程预防措施。创新点:利用物理模型实验,结合理论解析推导,得到高扬程虹吸管内空气累积的原因及关键影响因素,突破高扬程虹吸排水在少雨地区的使用局限,给出其长期适用的工程设计条件,对其在实际边坡工程中的推广应用提供理论技术指导。方法:通过物理模型试验,揭示长期停流虹吸管内出现空气累积的必然性;利用理论公式推导,对不同因素的影响结果进行对比分析,得出影响空气累积的主要因素。结论:1.溶于水的空气因压力降低而析出、管端空气溶入扩散到虹吸管顶部及温度变化引起空气析出等现象是无法避免的;其中,原有空气的析出及温度变化引起的空气累积是主要因素;2.边坡虹吸排水设计时进水端口距控制水位至少应预留2.05 m的地下水位上升余量,或者保持出水口的高程比进水口高程低4.1 m来保证析出空气段处于下水管中。

In this study, air accumulation at the top of a long-term-high-lift motionless siphon hose due to air dissolution and diffusion is studied. Many factors can induce air accumulation in siphon hoses during dry seasons. In this study, effects of the unavoidable factors, such as air diffusion and dissolved-air release, are investigated. Based on experimental observations and theoretical analysis, the following results are obtained： （1） pressure decrease in high-lift siphon hoses will cause release of su- persaturated air and induce a maximum 1.5 m long air column at the top of the siphon hose; （2） temperature increase will cause a maximum 0.55 m long air column; （3） air diffusion from water will lead to a less than 0.01 mm increment of the air column per day, which is considered to be negligible compared with that induced by air release due to pressure and temperature variations. Results indicate that high-lift siphon drainage can also be effectively used in arid districts. During siphon drainage design, at least 2.05 m long space to the safety level should be left for underground water rise, or the outlet should be kept 4.1 m lower than the inlet to guarantee that the released air will be gathered in the descending hoses.