Print Email Facebook Twitter Autonomous dredging of mud Title Autonomous dredging of mud Author Swart, R.N. Contributor Van Rhee, C. (mentor) Van der Schrieck, G.L.M. (mentor) Miedema, S.A. (mentor) Kollen, J. (mentor) Faculty Civil Engineering and Geosciences Department Hydraulic Engineering Programme Dredging Engineering Date 2015-12-07 Abstract There are many locations where the accumulation of mud poses a problem. In lakes it can have a negative influence on the ecological situation and in port basins it can hinder traffic. Usually these mud deposits are removed periodically with regular dredging vessels. Looking at the continuous nature of the mud deposition and at the trend of an increasing autonomy of machines, an interesting question is whether and how this mud can be removed by autonomous dredgers. A literature study on dredging processes and their application in both existing and conceptual machines was conducted to find potential solutions. The most viable concept is based on water injection dredging (WID), which is a dredging technology that uses water jets to fluidize the soil. This is done by injecting a high volume of water at a low pressure into the soil. The created soil-water mixture flows away under the force of gravity. A model was set up to describe the full WID process. In this model parts of available models are combined with new insights and approximations. Firstly, the jetting and loosening of mud is described. The jet intrusion depth is estimated using a perpendicular intrusion model. It is assumed that a jet intrudes into the soil up to a depth where the thrust pressure is equal to about 6 times the cohesion of the soil. Using the hauling velocity of the dredge the discharge, density and velocity of the mixture are estimated. Secondly, a transition from a supercritical to a subcritical flow takes place. In previous reports it was thought that entrainment and a hydraulic jump take place after the jetting process, although these effects are not clearly visible in experiments. Probably the only way to get more insight into the processes at this location is advanced fluid modelling. Therefore, the previously used methods to calculate entrainment and the hydraulic jump are not applied in this report. Since it can be assumed that at least some entrainment takes place during this phase, a multiplication factor is applied on the jet discharge to model the entrainment of water. The third and last sub process deals with the outflow of the density current. To come to an estimation for the travel distance of the density current, the Chézy formulation is applied, altered with a term to account for the reduced effect of gravity under water. Using an estimation for the settlement velocity, the decrease of mud discharge is taken into account. This gives reasonable results for the properties of the density current and the distance over which this current propagates. For the AWID (autonomous WID) device itself several options for the propulsion, energy supply and form factor have been considered. A small and floating device seems to be the most realistic. A device with a jet beam of 4 m, 500 kW installed power, a 2000 kWh battery pack and therefore a working time of four hours is a realistic option. A case study has been done on the Botlek harbour in the Port of Rotterdam. Using available data on the yearly volume of dredged material and the distribution of this material over the basins, an estimation has been made for the production of the AWID in this harbour. Extrapolating the results to the full Port of Rotterdam results in a system of six AWID devices that each serve their own area around one of the six docks that are locations throughout the port. Subject dredgingautonomouswater injection dredgingWIDmud To reference this document use: http://resolver.tudelft.nl/uuid:56d31a63-975d-4cd3-8c99-ea20f46202a8 Part of collection Student theses Document type master thesis Rights (c) 2015 Swart, R.N. Files PDF Thesis_Rob_Swart_december_2015.pdf 5.83 MB Close viewer /islandora/object/uuid:56d31a63-975d-4cd3-8c99-ea20f46202a8/datastream/OBJ/view