Optimum layout of weep holes in concrete irrigation canals to control uplift pressure and hydraulic gradient

In this study, the effect of weep holes on controlling uplift pressure and hydraulic gradient under concrete canals was investigated in different groundwater levels. For this purpose, three weep holes were embedded in different locations and combinations on the bottom and the sidewall of a laboratory canal. The amounts of seepage discharge were measured from these weep holes in single and combined modes. The corresponding values of seepage discharge, uplift pressure, and exit hydraulic gradient were calculated through simulation with the Seep/W model. The comparison of the observed and the simulated seepage values was indicative of the model's high accuracy with a mean error of 6.23%. The results showed that uplift pressure values in the single modes of weep holes in three different groundwater levels are similar. Uplift pressure in the binary combinations had a significant reduction compared to the single modes (an average of 73%). The maximum exit hydraulic gradient occurred at the weep hole located at the corner of the canal bottom. In general, the binary combinations of the weep holes were the best choice in terms of the minimum uplift pressure and the suitable exit hydraulic gradient.