Hydraulic gradient analysis on embankment dam foundation associated with internal erosion

Internal erosion is susceptible to occur in conditions where there are cracks or pre-formed cavities at the interface between the dam foundation and embankment. The initiation of internal erosion is related to the critical gradient (I_c ) and hydraulic gradient (I_xy ) at a certain position. The addition of repair materials in foundation improvement will change the total head, especially on the dam foundation, so the value of the hydraulic gradient will also change simultaneously from upstream to downstream. This study examines the value of the hydraulic gradient (I_xy ) at certain points on the dam foundation under the condition of foundation with and without improvement. Several scenarios were simulated using Geostudio Seep/W software to get an estimated value of the hydraulic gradient. The upstream blanket foundation improvement method increases the hydraulic gradient in the upstream zone when compared to the curtain grouting method, thereby increasing the potential for internal erosion in a related area. Increasing the depth of curtain grouting from 25 m to 35 m does not significantly reduce the value of the hydraulic gradient in the dam foundation. Research results can be used for analysis to improve design and construction, and as a reference for similar dams.