Abstract: In order to solve problems of low compressibility, poor toughness, and easy fracturing and destruction of high-water filling materials in gob-side entry retaining, performance improvement tests for such materials were carried out. Effects of different amounts of foaming agents, different fiber lengths and amounts on expansion rate and strength of materials were studied, and orthogonal tests were designed. At the same time, mechanical properties and microstructure of the materials before and after improvement were compared and analyzed. The results show that 1.5∶1 of water-cement ratio, 0.03% of foaming agent, 0.6% of polypropylene fiber, and 1% of compound early strength additive make the optimal proportion for high water filling materials featured with good uniformity, expansibility as well as greatly improved compressibility and integrity. Inside the improved samples, bubbles and interspersed fibers are densely distributed. And admixtures have no adverse effects on bearing structures, such as ettringite, main hydration product of high-water filling materials.

Key words: high water material, expansion, orthogonal test, toughness, microstructure