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Table 2 Summary of key parameters, objectives, and main results obtained from each phase

From: Large-scale inflatable structures for tunnel protection: a review of the Resilient Tunnel Plug project

Phase Key Inflatable Plug Features Testing Objectives Test Scale / Location / Validation Main Results
Phase 1: 2007–2008 • Fitted plug geometry
• Low-strength material
• Low-pressure air inflation only
• Demonstrate installation and storage outside of the dynamic envelope.
• Demonstrate adequate deployment time.
• Demonstrate the ability to obtain acceptable tunnel seal.
• Establish working relationships with potential end-user organizations.
Reduced scale (1:5.7)
Laboratory see-through scale model
Inspection and smoke testing
Understanding of deployment dynamics. Several trials with different plug shapes demonstrated the sealing capacity of each shape.
Full scale
Laboratory tunnel mockup
Inspection and timing
Installation procedures demonstrated; deployment timing established.
Full scale
Transit rail tunnel
Inspection, timing, and smoke testing
Installation completed within established time and space requirements; deployment within the required time; indication of ability to achieve an adequate seal.
Phase 2: 2009–2010 • Fitted plug geometry
• High-strength, single-layer material
• Full-pressure water inflation against floodwater pressure
• Design and construction of full-scale pressure-capable testing apparatus.
• Demonstrate deployment time to full pressure.
• Demonstrate the ability to achieve acceptable tunnel seal under pressure.
• Identify the advantages and limitations of single-layer plug design.
Reduced scale (1:4)
Quarter-scale testing apparatus
Inspection and pressurized water testing
Frictional properties adequate to withstand flooding water pressures with an acceptable leakage rate.
Full-scale surrogate
Full-scale tunnel mockup
Inspection and timing
Installation procedures demonstrated; deployment timing established.
Acceptable deployment; sizing established for final Phase 2 full-scale plug.
Full-scale Vectran fabric
Full-scale tunnel mockup
Inspection, timing, and pressurized water testing
Frictional properties proved to withstand flooding water pressures, but the strength of single-layer material found to be insufficient to withstand full pressurization.
Phase 2b: 2011–2012 • High-strength, multi-layer material
• Cylindrical plug geometry
• Full-pressure water inflation against floodwater pressure
• Demonstrate the ability of the cylindrical plug to conform to tunnel geometry.
• Demonstrate the ability to handle a heavier, thicker membrane construction while improving plug deployment and sealing characteristics.
• Demonstrate the ability to achieve acceptable tunnel seal under pressure.
• Remain stable under water flooding pressure.
Full-scale surrogate
Full-scale tunnel mockup
Inspection, timing, and smoke testing
Acceptable deployment; sizing established for final Phase 2b large-scale plug.
Quarter scale
Quarter-scale testing apparatus
Inspection and pressurized water testing
Frictional properties adequate to withstand flooding water pressures with an acceptable leakage rate and no slippage.
Full scale
Full-scale tunnel mockup
Inspection, timing, and pressurized water testing
Frictional properties have proven to withstand flooding water pressures with an acceptable leakage rate and sufficient plug strength.
Phase 2b-ET: 2012–2013 • High-strength, multi-layer material
• Cylindrical plug geometry
• Full-pressure water inflation against floodwater pressure
• Integrate plug with a modular, soft-pack container for improved installation characteristics.
• Demonstrate repeatability of successful plug deployment and plug conformity to provide adequate tunnel seal.
• Evaluate the impact of changes in plug oversizing ratio.
• Establish a range of acceptable leakage rates measured during full-scale flooding simulations.
Full-scale surrogate
Full-scale tunnel mockup
Inspection and contact sensors, timing
Repeatable, acceptable deployment and conformance to tunnel geometry.
Full scale
Full-scale tunnel mockup
Inspection and contact sensors, timing, and pressurized water testing
Repeatable, acceptable deployment and conformance to tunnel geometry, ability to withstand floodwater pressures with acceptable leakage rate and sufficient plug strength.
Quarter scale
Quarter-scale testing apparatus
Inspection and pressurized water testing
Tradeoffs in plug frictional and sealing properties with adjustments in plug oversizing.
Phase 3: 2013–2017 • Refined prototype plug and container
• An automated prototype inflation system
• Full-pressure air inflation against floodwater pressure
• Move tunnel mockup to the plug manufacturer location for full-pressure air inflation testing.
• Modify tunnel configuration to a representative configuration.
• Integrate refined plug and container with prototype inflation system.
• Demonstrate full-pressure air inflation.
• Demonstrate repeatability of system performance in prototype configuration.
• Demonstrate long-term system operation and performance.
Full scale
Relocated, reconfigured tunnel mockup
Inspection, timing, and pressurized floodwater testing
Reliable deployment and inflation within the required time; demonstration of the operation of the fully integrated system; verification of required frictional and sealing properties.
Demonstration of ability for long-term (21 days) continuous performance of the system.