Various types of equipment can be used, depending on the ground conditions and the project: kelly-mounted or hang grab, KS 3000 or Hydrofraise. The widths can vary from 0.52 to 1.52m : standard widths are 0.62, 0.82, 1.02 m.
Depths of 35 to 50 m are commonly achieved. The Hydrofraise can reach 150 m.
Operations generally proceed with adjacent primary and secondary panels.
The length of panels may vary from 3 to 20 m : 5 to 6 m is the common average size.
JOINTS: In most cases, use is made either of stop-end casings or Stopsol-type joints which are withdrawn once concreting of the primary panel is completed or CWS-type joints with lateral withdrawing. With the Hydrofraise, it is also possible to dig short secondary panels with the cutters biting in the concrete of the adjacent primary panels, thus making a direct concrete to concrete joint.
QUALITY CONTROL: Quality control must be carried out at each stage of the operations:
- excavation: quality of the slurry, verticality and width of the trench
- accuracy of positioning the steel reinforcement cages
- concreting: quality of concrete (slump) and volume vs depth follow up
- continuity: proper interlocking between primary and secondary panels.
Cross-section showing an example of a diaphragm-wall installed in difficult urban conditions