POSSIBILITIES OF TESTING SEAMS IN SINGLE-LAYER PLASTIC SEALS IN TUNNEL CONSTRUCTION

UNTERSUCHUNG DER MOEGLICHKEITEN ZUR NAHTPRUEFUNG BEI EINLAGIGEN KUNSTSTOFFABDICHTUNGEN IM TUNNELBAU

THE INCREASING USE OF PLASTIC SEALING MATERIALS IN TUNNELS AND ASSOCIATED ON-SITE JOINTING HAS RESULTED IN THE NEED FOR A RELIABLE TEST METHOD FOR SITE JOINTS. A VARIETY OF METHODS ARE CURRENTLY IN USE. THESE INCLUDE TESTING WITH HIGH TENSION ELECTRIC CURRENTS WITH COMPRESSED AIR OR WATER, BY VACUUM OR BY ULTRASONIC METHODS. IN ADDITION TO THE CHECKING OF THE QUALITY OF THE SEAM OVER ITS ENTIRE LENGTH, MECHANICAL LOADING CAPACITY OF THE WELDING MUST ALSO BE ESTABLISHED. SUFFICIENT EXPERIENCE AND KNOWLEDGE HAS NOT YET BEEN GAINED TO DETERMINE THE MOST EFFECTIVE TESTING PROCEDURE. THIS SHOULD, ON THE ONE HAND PROVIDE A RELIABLE REPORT ON THE EFFICIENCY OF THE WELDED SEAM TAKING INTO ACCOUNT THE LONG TERM LOADING. ON THE OTHER HAND, THE TESTING CRITERIA SHOULD NOT BE SO HIGH, THAT DAMAGE AT THE WELDED SEAM CAN NEVER BE EXCLUDED. A TEST PROGRAMME IS PLANNED, IN WHICH THE VARIOUS TESTING METHODS WOULD BE CHECKED UNDER CONDITIONS WHICH OCCUR ON BUILDING SITES. THE AIM OF THE STUDY IS TO DETERMINE THE WEAKNESSES IN CURRENT KNOWLEDGE ON THE EFFECTIVENESS OF VARIOUS METHODS OF JOINT TESTING UNDER BUILDING SITE CONDITIONS.