Experimental study on optimizing the ratio of EICP solution to reinforce Red-mudstone based on response surface method

In order to explore the effect and mechanism of urease-induced calcium carbonate precipitation ( EICP ) technology on the solidification of red mudstone fillers,urease was extracted from soybean, and the ratio of EICP solution was optimized by response surface method.The curing effect of EICP solution under the optimized ratio was tested by unconfined compressive strength test, expansion test, permeability test and crack development test under dry-wet cycle.The curing mechanism was explained by XRD and NMR experiments.The results showed that the optimized process parameters were as follows: the ratio of gum to enzyme was 1.5:1, the concentration of urease was 100g/L and the concentration of cementing solution was 1.4mol /L.The unconfined compressive strength of the sample under the optimized ratio is 55.21% higher than that of the plain soil.The free expansion rate and the loadless expansion rate is decreased by 25.10% and 45.65%, respectively.The saturated permeability coefficient is reduced by 90.54%.The cracks of red mudstone filler samples are greatly reduced after dry-wet cycle.The content of calcium carbonate in the red mudstone filler increased significantly after curing,and the generated calcium carbonate played a role in pore filling, reducing the number of large and medium pores in the samples.The research results provide a reference for the engineering application of EICP technology in red mudstone filler.