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618 m Vertical Shaft Steel Lining of Uma Oya Project, Sri Lanka

618 m Vertical Shaft Steel Lining of Uma Oya Project, Sri Lanka


A. Eliassi / A. Rahbar Farshbar

Uma Oya Multipurpose Development Project is a hydropower project comprises of two RCC Dams which their reservoirs are connected by a Link tunnel. The water will transfer from first dam reservoir to the other and then it will transferred through a 15.4 km headrace tunnel to the top of a 618 m deep vertical pressure shaft. This shaft provides high pressure water with its suitable head for an underground powerhouse which is designed to generate 120 MW electricity by two Pelton turbines. In this project, Raise Boring Machine utilized to excavate the vertical shafts including the Pressure Shaft. There was no middle access (adit tunnel) neither during the excavation nor steel lining of the Pressure Shaft. During the shafts pilot drilling and reaming of raise boring, numerous unforeseeable conditions occurred which resulted to a change in the design of the shaft support as well as prolongation of the excavation works with inefficient progress rate. This paper reviews the engineering and methodology of the Pressure Shaft which finally changed the lining of the Shaft from concrete type to steel lining. In this project, with an innovative method, 618 m Steel lining installed from top to bottom (hanging 1000 ton from top without any anchorage to the wall).

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Year 2022
City Copenhagen
Country Denmark
ISBN 978-2-9701436-7-3