A siphon drainage system with variable diameters for landslides: Concept, calculation, and validation

Abstract Drainage is a very effective form of remedial treatment for many landslides. In recent years, siphon drainage technologies have made great progress for landslides, and siphon pipes with a diameter of 4 mm are recommended to ensure that the siphon drainage runs continuously. Based on theoretical analysis for the flow velocity of a siphon, this study proposes a new siphon drainage system with variable diameters for landslides to improve the drainage capacity of the existing siphon drainage systems. In addition to the basic concept of the new siphon system, the estimation method of the drainage capacity of the new system is also developed. A series of experimental tests are conducted to verify the new siphon drainage system and the estimation method of the drainage capacity. The experimental results show that: (a) for all siphons with variable diameters, the calculated values are very close to the experimental measurements, and all of the error rates are less than 4%; (b) therefore, the developed calculation method of the velocity of a siphon with variable diameters is validated; (c) for all schemes with variable diameters, the increase rate of velocity ranges 15% and 116% comparing with those with constant diameters; and (d) the promotion effect brought by variable diameters for higher lift siphons is obviously better than that of lower lift siphons. Finally, an ancient landslide located in Zhejiang province, China, is used as a sample to illustrate how to design a siphon with variable diameters.