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Physical Investigation of Air Pocket Release in Below Grade Storage Tunnels

Author(s): James W. Lewis; Steven J. Wright

Linked Author(s): Steven Wright

Keywords: No Keywords

Abstract: The temporary storage of stormwater or combined sewage in below grade tunnels is useful in urban areas to prevent flooding. Several geyser events have occurred in existing systems resulting in the return of contaminated water to the ground surface. Previous investigations have shown that rapid filling of the tunnel, such as during large storm events, commonly results in the formation of discrete air pockets. It is hypothesized that the release of large air pockets through vertical shafts is responsible for geyser events. A laboratory investigation was performed to study the release of discrete air pockets from a horizontal tunnel. Visual observations reveal that large discrete air pockets can lead to strong geyser strengths over 10 times the tunnel diameter at the laboratory scale. A geyser mitigation scheme consisting of a diameter expansion within the vertical shaft is also explored. Preliminary results show that this strategy is very successful under certain conditions but requires further optimization.


Year: 2009

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