The utilization of dredged sludge can reduce environmental pollution and save land resources. To explore using sludge resources in ecological slope-protection projects, dredged sludge was incorporated into ecological slope-protection soil. Cynodon dactylon was planted to analyze the effect of sludge content on its growth. Direct-shear tests on the slope-protection soil with and without Cynodon dactylon were conducted to elaborate on the effect of sludge content, water content, and roots on the mechanical properties of the sludge-clay mixture. When the sludge content was <50%, Cynodon dactylon's growth improved with the sludge content increase, but at >50%, the sludge content's effect was meagre. As the sludge content increased, the cohesion and internal friction angle of the sludge-clay mixture without roots decreased, lowering the shear strength. The soil's cohesive force and internal friction angle follows the sequence: natural state with roots > natural state without roots > saturated state with roots > saturated state without roots. The cohesion and shear strength of the sludge-clay mixture with roots increased at first before decreasing with an increase in sludge content, optimized at 50% sludge content. Here, the ecological slope stability was the best, meaning that the optimum sludge proportion was 50%.
Keywords: Cynodon dactylon; Ecological slope protection; dredged sludge; growth characteristics; mechanical properties.