Feasibility Study of Low-Environmental-Load Methods for Treating High-Water-Content Waste Dredged Clay (WDC)-A Case Study of WDC Treatment at Kumamoto Prefecture Ohkirihata Reservoir in Japan

The effective and sustainable treatment of high-water-content waste dredged clay (WDC) remains a significant challenge in water conservancy engineering. In this study, we focused on the treatment of WDC produced by Kumamoto Ohkirihata Reservoir. The study examined the effect of two types of cement-based solidifiers, namely, ordinary Portland cement (OPC) and cement-fly ash agent (DF), on three clay samples collected from different locations. The cone index test was used to assess the samples' properties. The dosage of cement required for effective improvement with DF was significantly reduced (by about 47-55%), compared to OPC. Moreover, the dewatering efficiency of WDC improved by the simple dewatering method of vertically placing environmental protection materials. Within seven days, the average water content of the WDC decreased to below the liquid limit compared with natural air drying. Finally, the dosage of DF required to stabilize the WDC under effective improvement conditions was reduced by 37-58%, which is higher than the dosage of OPC reduction (22-50%). The reduction in water content reduced the pore space of the soil particles, benefiting the internal bonding of DF-stabilized clay. Dewatering methods facilitate the use of DF solidifiers, facilitating sustainable and environmentally friendly improvement in WDC.