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

Abstract

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.

Reuse of Lake Sediments in Sustainable Mortar

“…The damming of watercourses leads to the interception and subsequent deposition of transported solid particles, resulting from the phenomenon of bank and bottom erosion, due to the reduced kinetic energy of the water current [1][2][3][4][5][6]. This dynamic results in the accumulation of millions of cubic meters of sediment within the reservoir, generating a dead volume that reduces the available water storage capacity and makes the reservoir capacity non-renewable [7][8][9][10][11]. The need to dredge the accumulated sediment, however, is at odds with effective sediment management, partly due to the introduction of various regulations that have complicated the usual practices of dumping at sea or depositing it on land without a comprehensive characterisation plan [12].…”