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

As a result of the siphon phenomenon in soft soil siphon drainage, groundwater is discharged from the soft soil without any 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 the model test presented in this study, the decrease in the groundwater level is more pronounced when the spacing of the siphon holes is smaller. In comparison to the single-hole test, the spacing of 0.4 m is 107.6% larger. Based on subsequent numerical simulations, it has been found that when the hole spacing is reduced to 1.0 m, the decrease in the groundwater level on the 60th day can reach the limit value of 10 m for soft soil with a permeability coefficient of 10−9 m/s. In addition, the field test indicates that the average decrease in the water level of the 0.9 m hole spacing is 75.9% greater than that of 1.8 m, while the time required to reach the same decrease in the water level is 63.6% shorter.