An Investigation Of High-lift Siphon Flow Velocity In A 4-mm Siphon Hose

Most landslides are trigged by the rise of groundwater level by rainfall infiltration.Groundwater can increase the weight of the soil,soften the soil and decrease the shear strength of the soil,affecting the stability of slopes.Therefore,groundwater drainage has been a frequently-used method for landslides.The present measures for long-term drainage,however,are not good enough owing to low performance ratio.By contrast,high-lift siphon drainage is a free-power,long-term and economical approach which has the irreplaceable advantage for slope drainage.An intense cavitation occurs in the siphon hose for high-lift siphon drainage,forming the gas-liquid two-phase flow.With the investigation of gas in the siphon hose and the theoretical analysis of long-term stationary siphon flow,the released gas in siphon hose can be calculated and the effect for siphon drainage can be evaluated.At present,High-lift siphon drainage by 4-mm internal diameter siphon hoses is a real-time,free-power and long-term approach for slope drainage.The conventional hydraulics formula for pressurized pipe flow is generally used to calculate the single-phase velocity of siphon flow.However,an intensive cavitation phenomenon occurs in the high-lift siphon hose and then a two-phase flow is formed.Research on the velocity of high-lift siphon flow is a prerequisite for the application of siphon drainage with a 4-mm siphon hose.Few investigations of this subject have been carried out.And the water discharge capacity of a single siphon hose is low,but there is a need to ensure the number of siphon hoses to satisfy the requirements of slope drainage.Hence,experiments on the high-lift(8m?H0?10.3 m)siphon drainage in a 4-mm siphon hose were performed.The characteristics of siphon flow under different conditions were observed and test data were obtained.Comparisons between test results and calculated results showed that significant errors were given by the hydraulics formula.It is demonstrated that the effect of gas in a siphon hose should be included in the calculation of flow velocity.With the combination of the low-lift siphon flow velocity formula and test data,high-lift siphon flow velocity in a 4-mm siphon hose can be derived by the method of theoretical analysis and numerical fitting.The findings can be used to determine the number of siphon hoses and layout of siphon drainage holes,and provide valuable information for geotechnical companies.