Mechanical properties of soil reinforced by fiber and alkaline-activated rice husk ash, and rainfall erosion model tests.

Rice husk ash is an industrial waste produced by biomass power plant to generate electricity, which contains a lot of silica. The accumulation of rice husk ash not only consumes land resources, but also causes environmental pollution. It is an urgent problem to explore the resource utilization of rice husk ash. In order to reuse rice husk ash, this study focuses on the application of polypropylene fiber and alkaline activated rice husk ash to slope reinforcement. Polypropylene fiber has the advantages of good toughness and corrosion resistance. Reinforced soil can effectively improve soil toughness and mechanical properties of soil engineering. NaOH solution was selected as the alkaline activator, and rice husk ash and polypropylene fiber were used to stabilize and strengthen the clay, which was consistent with the principles of sustainable development and circular economy. Through unconfined compressive strength test, the effects of ash content, polypropylene fiber content, NaOH concentration and curing age of rice husk on soil strength characteristics were studied. In addition, the mechanical properties and curing reinforcement mechanism of alkali-activated rice husk ash fiber-reinforced soil were studied by using dry-wet cycle test, rainfall erosion model test and microstructure analysis. The results show that the curing effect is best when 5 % rice husk ash is used, and the unconfined compressive strength of rice husk ash reinforced soil is the highest when the fiber content is 0.7 %. NaOH solution improve soil strength, with maximum strength observed at a concentration of 0.6 mol/L. The resistance to dry-wet damage of rice husk ash fiber reinforced soil is better than that of unreinforced soil, but the strength loss after dry-wet cycle by alkali activation is greater. In addition, the surface erosion of fibrous soil slope is the smallest, and the erosion amount is much lower than that of unreinforced soil. Fiber can effectively improve the erosion resistance and slip resistance of slope. The microscopic test analysis confirms the strength test results, and the addition of 5 % rice husk ash will produce more hydration products, reduce soil porosity and improve soil strength. NaOH can effectively stimulate the active ingredients in soil particles, and the hydration products produced by the reaction can effectively fill the soil pores and significantly enhance the soil strength. The staggered network structure of polypropylene fibers improves the integrity of the soil, providing significant reinforcement.