Abstract: In order to realize the utilization of the two solid waste resources of oyster shell and residual soil, it was proposed that the pretreated oyster shell was activated by phosphoric acid or diammonium hydrogen phosphate (DAP) to obtain the oyster shell solidified soil. The mechanical properties of oyster shell solidified soil with different ratios were measured and the scouring resistance of slope was studied. The scanning electron microscope and X-ray diffraction were used to observe the microstructure of solidified soil and analyze its solidification mechanism. The results show that the addition of phosphoric acid or DAP improves the compressive strength of oyster shell solidified soil, and the effect of adding DAP is better. The best ratio (mass fraction) of materials is: 73.6% soil, 18.4% oyster shell (particle size ≤1 mm), 8% DAP. Under the optimum ratio condition, the drying compressive strength reaches 2.14 MPa, which is 2.43 times of the compressive strength of oyster shell stabilized residual soil, and the softening coefficient reaches 0.5, which changes the disintegration characteristics of the original soil when exposes to water.In indoor slope scour test, the oyster shell solidified soil mixed with DAP effectively reduces the amount of sand produced by the erosion of slope compared with the plain soil. Microstructure analysis shows that phosphoric acid or DAP interacts with oyster shell to form calcium phosphate crystals and hydroxyapatite. The new products can cement soil particles and solidify the soil.

Key words: residual soil, activated oyster shell, solidified soil, scouring resistance of slope, solidification mechanism