Influence of cracking conditions on seepage performance of alkali-activated geopolymer linings in earthen canals

Abstract

Water seepage from earthen canals severely reduces irrigation efficiency. This study evaluates an alkali-activated fine-ash geopolymer as a canal lining material and investigates how lining cracks affect seepage. Laboratory tests assessed soil hydraulic conductivity across varying fine-ash contents and curing periods, while SEEP/W finite element modeling simulated seepage performance under different configurations, water levels, and crack conditions. Results show that higher fine-ash content and longer curing periods significantly decrease hydraulic conductivity. The optimal mixture (30% fine ash, 28-day curing) reduced hydraulic conductivity from 1.0×10-6 m/s to 2.91×10-8 m/s, yielding a 97% reduction in seepage losses. Full geopolymer lining decreased seepage discharge from 1.2 m3/day/m (an 89.9% reduction), whereas bed-only lining reduced it by 62.5%, indicating the bed accounts for roughly 70% of losses. Numerical analysis further demonstrated that seepage increases with higher water heads and greater crack dimensions, with bed cracks causing the most severe losses. Ultimately, alkali-activated fine-ash geopolymer emerges as a highly effective material for controlling canal seepage.