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

Paper

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The Tension Track Milled Joint (TTMJ) is a system under development for forming joints between slurry (diaphragm) wall panels. Developed by Trevi, Arup and CCMJ Systems with EU Horizon 2020 support, it aims to address the difficulty of removing conventional stop-ends at greater depths and the limitations of joints cut by hydro-mills, which typically cannot accommodate waterstops or strong shear and tension connections.<br /><br />The system uses guide tracks fixed to the reinforcement cage of a primary panel. After an adjacent secondary panel is excavated, a tracked trimmer follows the guides down the concrete face, removing a controlled layer of concrete and a sacrificial part of the tracks. The resulting joint follows the primary panel’s profile, helping maintain alignment and concrete-to-concrete contact. The joint can be shaped to provide a shear key and may include a waterstop and a tension connection across panels.<br /><br />The proposed advantages include more reliable joints at greater depths, reduced dependence on stop-ends, improved shear and tension transfer, and greater flexibility in reinforcement and panel layouts. The system may also enable smaller-diameter shafts and reduce construction costs and duration. In a London shaft tender example, the authors estimated that using TTMJ could reduce the scheduled construction duration by 40% and cost by 20%, compared with the proposed conventional approach.<br /><br />At the time of the paper, the trimmer, guide tracks and joint components were still being developed and tested. Laboratory testing and full-scale trials at Trevi/Soilmec’s 20 m-deep facility were planned, followed by validation and industry accreditation.<br /><br />The authors present TTMJ as a potential step-change in slurry-wall joint construction, particularly for deep walls and confined urban shaft projects.

Keywords

Tension Track Milled Joint

TTMJ

slurry wall panels

diaphragm wall

guide tracks

tracked trimmer

waterstop

shear key

tension connection

deep excavation