Water Injection Dredging and Fluid Mud Trapping Pilot in the Port of Rotterdam

Abstract

As conventional dredging and relocation of sediment deposits is highly expensive, port authorities seek for more efficient solutions for reducing the costs of maintenance dredging. One of the well-known solutions is water injection dredging (WID). In general, WID is proven to be cheaper than the hopper dredging by leaving the sediment in place, thus, eliminating substantial costs for relocation of the dredged sediment.

In autumn 2018, the utility of WID and fluid mud trapping was investigated in the Port of Rotterdam. As a first step, the sediment trap was made in the Calandkanaal. Next, the WID actions were carried out for fluidization of the top layer sediment around the deepening and horizontal transport of the fluidized mud into the sediment trap. The WID actions were monitored by means of multi-beam and single-beam echo-sounding surveying methods at low (15-38 kHz) and high frequencies (200-400 kHz). After WID has taken place, the sediment trap was regularly surveyed for 3 months. Apart of abovementioned echo-sounding surveying methods, different penetrometers were used for monitoring the settling and consolidation processes in the sediment trap. We used Graviprobe, Rheotune and DensX for measuring the shear strength, the yield stress and the density of sediment, respectively. These measurements were compared to the ones in laboratory, where the densities and the yield stresses of sediment samples were measured independently.

It was concluded that the water injection dredging method can be efficiently used for fluidizing and transporting weak fluid mud layers. In-situ measuring tools are available for characterizing the behavior of fluidized sediment. Based on our experimental investigation, it can be concluded that new cost-effective port maintenance strategy is feasible in the port.