Analysis of the influence of siphon hole spacing on soft-soil drainage effect

Abstract

In soft-soil siphon drainage, due to the siphon phenomenon, groundwater is discharged from the soil without the need for power and this increases the effective stress in the soil. A significant part of the drainage effect is determined by the spacing of the siphon holes. According to model tests carried out in this work, the decrease in the groundwater level was more pronounced for a smaller siphon hole spacing. Compared with a single-hole test, a spacing of 0.4 m resulted in an improvement of 107.6% in the minimum groundwater level. Based on subsequent numerical simulations it was found that when the hole spacing was 1.0 m, the decrease in the groundwater level on day 60 reached the limit value of 10 m for soft soil with a permeability coefficient of 10−9 m/s. In addition, field tests indicated that the average decrease in the water level for a 0.9 m hole spacing was 75.9% greater than that for 1.8 m, while the time required to reach the same decrease in the water level was 63.6% less.