[abstract] Trimix Saturation with Excursions during the Western Scheldt deep tunneling project

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[abstract] Trimix Saturation with Excursions during the Western Scheldt deep tunneling project

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Title: [abstract] Trimix Saturation with Excursions during the Western Scheldt deep tunneling project
Author: Sterk, W; LePechon, JC; van Rees Vellinga, TP
Abstract: BACKGROUND: Two parallel tunnels are being constructed underneath the river Western Scheldt, with a diameter of 11.3 meters and a total length of 6.6 kilometers. The Tunnel Boring Machines (TBMs) got stuck at the deepest point (65 meters) and needed repairs to be done at an overpressure of 6.9 bar(G), partly in air and partly in bentonite. A saturation dive technique with excursions was chosen to solve the problems. METHODS: A saturation habitat was installed at the site near the tunnel entrance, consisting of two living quarters and several locks. For TUP to and from the TBMs, a special shuttle on a train was used. It was intended to use nitrox saturation with excursions on trimix for compressed air work up to 6 bar(G). For the present work at 6.9 bar(G), 1 bar of helium was added to reach a habitat pressure of 4 bar(G), with 0.4 bar O2 and 3.6 bar N2. The trimix for the excursions consisted of 12percent O2, 45percent N2 and 43percent He, allowing working times up to 4 hours. Decompression tables were calculated using a neo-Haldanian model. Decompression from excursion to habitat pressure was done on air, with the longest stop during the transfer in the shuttle back to the habitat. RESULTS: In total 111 men excursions were carried out uneventful, during 3 saturation runs with 2 teams of 3 divers each. During the first saturation decompression, with a calculated deco time of 3 days and 2 hours, 2 out of the 6 divers got a bend, 1 with a relapse after surfacing. Therefore, the table was recalculated, resulting in a total decompression time of 4 days and 10 hours. The following 2 saturation decompressions were without problems. CONCLUSIONS: Timex saturation with excursions appeared to be feasible for deep compressed air work in tunneling.
Description: Undersea and Hyperbaric Medical Society, Inc. (http://www.uhms.org )
URI: http://archive.rubicon-foundation.org/1016
Date: 2001

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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