Community Research and Development Information Service - CORDIS

Systems of Waterproofing for Existing Masonry-Lined Tunnels (SWET)

The Project was conceived after long standing appreciation of the problems associated with water ingress into existing masonry lined tunnels and the difficulty in stopping such ingress. Partners were selected from Portugal, Germany and United Kingdom, which provided a complementary and multi-disciplinary Consortium with the expertise required to address the problem. The aims of the project were to remove all visible water and to reduce the level of water in the tunnel lining to that where damage due to freeze/thaw cycling does not occur.

All the project work was carried out under a Quality Management System. The core activity of the project was to develop systems for waterproofing existing masonry lined tunnels but other support work was required for the core activity to be carried out. Tunnel condition evaluation and structural risk assessment knowledge was necessary for a suitable waterproofing system to be conceived. Non destructive testing methods were examined to provide detailed information about masonry lined tunnels but none were found which provided reliable data that was useful. The need to drill holes through the tunnel lining was recognised as the best method of evaluating conditions but the use of the endoscope to examine the lining and the void behind the extrados was seen as a positive advancement. During waterproofing trials, the intrados of the tunnel lining was monitored for movement to ensure a safe system of work. In addition, a complete Health and Safety plan was put in place for every site trial.

A variety of waterproofing trials were carried out in a disused railway tunnel. The methods used for the trials were identified and selected following Consortium brainstorming and included the country rock injection, void filling, brickwork injection and surface coating. Materials were selected and developed to provide the required rheological and cure characteristics and plant and equipment were chosen so that these materials could be mixed and placed in a controlled manner. The best results were achieved by void filling using cemetitious grout, but this trial had the advantage of a defined methodology and confidence borne out of discrete element analysis using the UDEC code. All visible water ingress was removed. Ingress of 4.5 litres/m²/hour was reduced by 90% by void filling and eliminated by a secondary treatment using brickwork injection.

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