Author(s): Otto Neshamar; Alan Cuthbertson; Oyvind Thiem; Peter Davies
Linked Author(s): Peter A. Davies, Alan J S Cuthbertson
Keywords: Rock dumping; Polydisperse settling; Debris flow; Scaled model experiments
Abstract: The Norwegian Public Roads Administration (NPRA), together with Bane NOR, are planning a new road and railway link between Bergen and Voss, including the construction of new tunnels along the southern and eastern shore of Sorfjorden. Excavations will generate O (107) m3 of blasted rock, much of which will require disposal within the fjord. A key environmental concern is the fate of fines present within the rock fragments, especially since Sorfjorden is a protected salmon fjord and has several fish farms sited close to planned rock disposal sites. Proposals for rock dumping strategies must therefore include appropriate mitigation measures to prevent dispersion of fine suspended particulate matter within the wider fjordic waterbody. Two rock disposal methods are tested within reduced-scale laboratory experiments at the University of Dundee: mass dumping via vertical fallpipes, and inclined shaft tunnels. In both cases, the dumped rock loads will exit the pipe/shaft at a significant depth within the fjord, with the expectation that the fines (typically <1% by weight) will deposit along with coarser rock fragments to the floor of the fjord, with minimal interaction with the surface waters. The main aim of the experiments is to characterise the dynamics of particles settling within the confinement of the pipe, and to assess the motion of fine particles exiting the pipe.
Year: 2024