Waterproofing Systems in Double-Shell Tunnels

Bonding Behaviour of Sheet Membrane, Geotextile and Shotcrete

Quelle/credit: Stefan Lorenz

1) Effective forces and general set-up of the sheet membrane system in the vault in keeping with the Austrian Society for Construction Technology (öbv) Guideline on “Tunnel Waterproofing” |

Quelle/credit: Stefan Lorenz

2) Producing the shotcrete samples on a tunnel construction site |

Quelle/credit: Stefan Lorenz

3) Grading curves for shotcrete |

Quelle/credit: Stefan Lorenz

4) Shotcrete sample on the left and corresponding negative on the right |

Quelle/credit: Stefan Lorenz

5) Photogrammetric assessment of the surface of a shotcrete sample |

Quelle/credit: Stefan Lorenz

6) Test set-up with pressure vessel |

Quelle/credit: Stefan Lorenz

7) Sheet membrane (on the left) and protective geotextile (on the right) after the pressure vessel test |

Quelle/credit: Stefan Lorenz

8) Testing unit set-up (on the left), protective geotextile (above right) and sheet membrane (below right) at 5 MPa |

Quelle/credit: Stefan Lorenz

9) Schematic presentation of the large-scale shear test |

Quelle/credit: Stefan Lorenz

10) Shear test |

Quelle/credit: Stefan Lorenz

11) Three-dimensional presentation of interconnection of shotcrete and sheet membrane |

Quelle/credit: Stefan Lorenz

Modelling the contact conditions between the outer and inner shell represents an important element in conjunction with numerical calculations of tunnel shells. Tests on the mechanical bonding behaviour of tunnel shells and waterproofing systems in double-shell tunnels have been carried out in the lab. The aim of these analyses was to ascertain the properties of waterproofing membranes and protective geotextiles when installed in the tunnel and when the bearing behaviour of the primary shotcrete shell is reduced. Towards this end, tests were executed in order to investigate the behaviour given various mechanical effects on the bonding system, consisting of shotcrete, geotextile, waterproofing/sheet membrane and inner shell concrete.

1 Introduction

Within the scope of long-term investigations of the supporting material for existing tunnels, sheet membranes from various tunnels were analyzed following life cycles of up to 40 years. In the process, it was established that the membranes, which are arranged between the outer shell and the inner one, revealed signs of damage. On the basis of the investigations, this damage phenomenon was examined more closely and the reasons for failure verified.

The failure of the sheet membrane can be attributed to different causes. Thus an error when installing the sheet membrane as e.g. when...