TTMJ - The New System for Slurry (Diaphragm) Wall Joints-Paper

Paper

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TTMJ (Tension Track Milled Joint) is a developing system for forming joints between diaphragm-wall panels, intended to overcome difficulties removing conventional steel joint formers at depths exceeding about 30 metres. It uses pultruded glass-fibre-reinforced polymer tracks cast into a panel’s ends. These tracks guide a milling machine that trims the hardened concrete to create the joint at depth.<br /><br />The system is designed to provide three functions: a reliably trimmed construction joint, an optional tension connection between adjacent panels using headed bars, and an optional water-stop using a PVC carrier and hydrophilic seals. The tracks also help guide the trimmer and are designed to withstand the forces exerted during cutting.<br /><br />Laboratory tests on more than 50 concrete blocks investigated track restraint, removal of the track’s sacrificial section, and the tension connection. Preliminary results indicated that the tracks could resist anticipated trimmer forces. In tests of the preferred tension-bar arrangement, two samples failed at 140 and 150 kN.<br /><br />At the time of the paper, a full-scale trial programme was planned at a 20-metre-deep test shaft in Italy. It would assess trimming of flat, sloped and bulging concrete faces, track pull-out resistance, concrete placement into the tracks, and the large-scale performance of the tension connection.<br /><br />The developers anticipate that TTMJ could enable deeper, more effective panel joints while improving water resistance and structural continuity. They also identify potential project cost savings of up to 20%, programme advantages, and improved safety and risk management. These benefits remain to be validated through the planned trials.

Keywords

TTMJ

Tension Track Milled Joint

diaphragm-wall panels

pultruded glass-fibre-reinforced polymer

joint trimming

milling machine

tension connection

water-stop

hydrophilic seals

diaphragm wall construction