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MTRC West Island Line Extension, Hong Kong - Sprayed Concrete Optimisation

Creating a watertight permanent sprayed concrete lining with a controlled drainage path for underground storage


Gammon Construction Ltd


Sprayed Concrete,Underground Logistics


Hong Kong

The Project 

The Mass Transit Railway Corporation (MTRC) had been undertaking an extension of the West Island Line (WIL) from Sheung Wan to Kennedy Town.  

Most of the tunnelling works were excavated using the drill and blast tunnelling methodology due to the geological conditions. An underground storage magazine had to be constructed within the close vicinity of the three working sites for the safe and dry storage of explosives. 

The magazine was placed in a 300 m horseshoe type tunnel with 10 separate storage rooms on Victoria Road on the west coastal side of Hong Kong Island. 

The Challenge 

The explosive storage rooms were required to be 100% watertight, with permanent lining using sprayed concrete. To ensure bonding of the sprayed concrete while still allowing systematic dissipation of ground water to a drainage system, sheet membrane could not be considered for various reasons associated with providing a watertight permanent sprayed concrete lining, bonding issues, and creating a controlled drainage path. 

Quick Facts

  • Sprayed concrete lining for an underground storage magazine in a coastal area
  • Creating a controlled drainage path with the required bonding performance
  • Site trials to demonstrate the effectiveness of TamSeal 800
  • Simple and flexible application even with limited supervision

The Solution 

Normet Hong Kong Limited, formerly TAM International Limited, introduced the TamSeal 800 EVA copolymer spray-applied membrane system. The system included the use of TamCrete TopShot, a smoothing gunite, and a double-sided geotextile drainage fleece that could be installed at 1.5 m intervals to allow any groundwater to drain from the crown to the invert drainage system at certain locations. 

Site trials were undertaken to demonstrate the effectiveness of the solution. Test panels were sprayed in sequence, commencing with the primary lining, followed by a smoothing layer of TamCrete TopShot. An application of single 3 mm layer of TamSeal 800 grey colour using a Normet Piccola, a dry shotcrete rotor machine was completed with a final 250 mm thick permanent sprayed concrete layer. Cores were taken through the panel to show the subsequent layers and bonding performance. The photos illustrate the core and consistency of the TamSeal 800 prior to the PSCL application. 

MTRC was satisfied that the TamSeal 800 system provided the suitability, ease and speed required to ensure the project was completed on time. The magazine rooms were excavated, and primary sprayed concrete support was installed. The geotextile drainage was installed using 1 m wide strips at 1.5 m centres, which included the headwall, and a single 500 mm wide strip running along the crown. 

Project Outcome

The TamSeal 800 system offered several advantages over alternative options considered. The speed of preparation, simplicity and flexibility of the application enabled the site construction team to deliver the lined, watertight sections of the project on time and within budget, with limited supervision from Normet. 

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