Self-weight sedimentation and consolidation characteristics of hydraulic-dredged slurry in Tianjin Binhai District

The model tests on hydraulic-dredged slurry with initial moisture content w₀ of 200%~2000% in Tianjin Binhai District after sedimentation of 100 days are performed to investigate the self-weight sedimentation and consolidation characteristics. The relevant indices for the hydraulic fill are suggested so as to provide reliable theoretical support for dredger filling projects at the design and construction stages. The results show that the settling of the hydraulic-dredged slurry in Tianjin includes two types, deposition settling and consolidation settling, respectively. The former undergoes flocculation, hindering settling and consolidation. The critical moisture content w₀^* is 400%, and there is a linear relationship between w₀^* and the liquid limit. When w₀≤w₀^*, the consolidation settling occurs, and the settlement can be calculated by using the one-dimensional consolidation theory. When w₀>w₀^*, the deposition settling occurs, and the settlement can be calculated by using the sedimentation rule. The void ratio of soil formation e₀^* is 10.92. The time of sedimentation stability can be calculated using T_c=159(w_0/ w_L)^-1. The void ratio of sedimentation stability can be calculated by the piecewise formulae e_c=0.08+5.4（e₀≥13.65）and e_c=0.4+1.03（e₀<13.65）. The flocculation yield stress P_s is 0.3 kPa and the boundary void ratio e_s is 6.4. The self-weight sedimentation and consolidation is the process that the flocculation yield stress and the effective stress influence each other, so that different settlement characteristics are aroused. The micro-structure of dredged mud in parallel direction to sedimentation is flocculation structure, and that in vertical direction to sedimentation is a stacked one.