Fly ash consolidation piles. The use of fly ash consolidation piles in soft soil foundations offers advantages such as reliable formation, freely selectable shapes, low cost, good foundation improvement effects, strong deformation resistance, and high pile density. Fly ash consolidation piles are made from fly ash, gypsum, and cement mixed with water, then pressure-injected into nylon bags to compact the surrounding soil. If necessary, the grouting pipe can be used for repeated secondary grouting from top to bottom. The nylon bag serves as formwork, filtration and dewatering, pressurization, and reinforcement. Owing to the pressure grouting and drainage measures, during the outward seepage of the grout, water can only seep outward through the micropores of the nylon bag and is isolated outside the bag, forming a uniformly consolidated and hardened pile body.