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Author(s):	Innerhofer, Guntram; Bickel, Lukas
Title:
Abstract:	As a result of several feasibility studies from which sound economic and technical arguments emerged, the decision was made to construct a new headrace system for the Rodundwerk I consisting of a low pressure tunnel, a shallow pressure shaft parallel to the surface slope and a subsequent high-pressure penstock gallery. The new distribution pipeline was designed as a concrete-encased gravity abutment. Construction started at the beginning of May 2020 and since then excavation work has progressed according to plan. Particular attention had to be addressed to the impact of construction operations on the existing power plant structures. Hence, a detailed monitoring concept was established concerning the vibration transmission in the rock mass. Excavation works are carried out partly by tunnel boring machine, partly by drilling and blasting and, once the critical threshold of vibration has been reached, by alternative methods. By continuously adjusting the blasting parameters (charge amount, ignition timing), it was possible to minimise the detonation-related effects in the vicinity of the existing structures. Umfangreiche Voruntersuchungen ermöglichten eine wirtschaftlich und technisch profunde Entscheidung zugunsten eines neuen Oberwassersystems für das Rodundwerk I mit einem hangparallelen, seicht liegenden Schrägschacht und anschließenden Flachstrecken. Die neue Verteilrohrleitung wurde als betonummantelter Massefestpunkt konzipiert. Der Baustart erfolgte Anfang Mai 2020. Die Ausbrucharbeiten sind planmäßig fortgeschritten. Besonderes Augenmerk musste auf die Einwirkung des Baubetriebs auf den Bestand gelegt werden, weshalb ein detailliertes Überwachungskonzept hinsichtlich Schwingungsübertragung im Gebirge angelegt wurde. Die Vortriebe werden teils mit Tunnelbohrmaschine, teils im Sprengvortrieb und ab Erreichen der festgelegten Grenzwerte für die zulässigen Schwinggeschwindigkeiten mit Alternativmethoden ausgeführt. Durch die laufende Anpassung sprengtechnischer Parameter (Lademenge, Zündzeitstufen) gelang es, detonationsbedingte Einwirkungen in Bestandsnähe so gering wie möglich zu halten.
Source:	Geomechanics and Tunnelling 14 (2021), No. 2
Page/s:	185-195
Language of Publication:	English/German

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