Tweet Share

• Send by email

  Send by email

  

  Segmental Lining Design Optimization Against Reliable TBM Thrusting Conditions

  TBM thrust is, in many precast segmental lining designs, the critical loading condition when deciding between only FRC (Fibres Reinforced Concrete) or hybrid solutions (fibres + steel conventional bars). Traditionally, the TBM (Tunnel Boring Machine) pushing value used as reference by designers, when structurally checking this temporary stage, has been the maximum (or exceptional) thrust installed to the machine. In addition, this common design practice is also supported by most of the relevant international tunnelling associations. Nevertheless, when examining TBM pushing records from excavations, actual thrusts are much lesser than the maximum capacity of the machine. In this respect, registered thrust loads from the Northeast Boundary Tunnel (NEBT, Washington DC) construction, lined with SFRC (Steel Fibres Reinforced Concrete) segments, are reviewed to motivate a discussion on the reliable TBM pushing load conditions to be considered in the design of circumferential joints. With the aim to propose a design that maximizes efficiency, three levels of loadings are then established: expected thrust according to tunnel conditions, to be verified with no cracking, maximum thrust, to be checked with admissible cracks and exceptional thrust, to be supported by additional reinforcement or reasonable repairs acceptance. Being the final goal of the paper an optimization of the reinforcement and thus a more sustainable segmental lining.

  Recipient :

  Name ^* :

  E-mail address ^* :

  ^* Required fields

  Send   or  Cancel

• Print