A diaphragm wall grab rig can excavate typical panels 600–1,800 mm wide, with panel lengths around 3.0–7.0 m and equipment-specific capacities up to 1,500 mm wide by 4,000 mm long [S2][S3].
Maximum depth is governed by the grab, crawler crane and excavation system: published equipment ranges extend from 10–75 m for panel depth, while 40 m is a common maximum and deeper walls are achievable [S6][S7].
Panel Width and Length: Verified Equipment Ranges
Casagrande gives maximum grab dimensions of 1,500 mm width and 4,000 mm length, with grab rotation of plus or minus 180 degrees [S2].
The maximum grab width describes the excavation bite, while the finished panel length describes the dimension of the completed panel. Keeping these dimensions separate helps explain why published panel dimensions can appear inconsistent across contractors.
For procurement, the useful working envelope is therefore not one universal panel size. Record the permitted trench width, maximum trench length, and maximum excavation depth as three separate ratings. A rig may handle a 1,500 mm-wide bite while its crane, mast and grab still limit usable depth.
Depth Capacity Depends on the Complete Rig
Panel thickness ranges from 350 to 1,200 mm, panel width from 2,000 to 4,200 mm, and panel depth from 10 to 75 m depending on the crawler crane and grab type [S6]. Wall thicknesses typically range from 600 to 1,500 mm, with depths of up to 40 m usual, although thicknesses of up to 2,000 mm and considerably deeper walls may also be used [S7].
Those figures describe different scopes and terminology. The 2,000–4,200 mm Soilmec range refers to panel geometry, while the 1,500 mm width in several grab specifications is the excavation-tool capacity. A multi-bite or special-shape arrangement can produce a finished panel wider than one grab bite, but the elements, joints, reinforcement and excavation sequence must all be designed for that arrangement [S4].
Depth selection should therefore start with the required wall elevation, then verify crane reach, grab operating length, hydraulic capacity, slurry system, guide-wall setup and panel stability.
Grab Selection by Soil and Wall Geometry
BAUER identifies soil conditions and trench depth as the primary factors governing whether to use a grab or trench cutter [S5].
A grab is not automatically the better choice for a deep wall in hard ground. The trench cutter loosens material with cutting wheels, transports it in slurry through a mud pump, and sends it through desanding equipment before slurry reuse [S5].
Multi-Bite Panels Expand the Geometric Options
A multi-bite arrangement changes the finished panel width and length but not the single-bite capacity of the grab. Corner and T-panel arrangements also require multiple bites [S4]. The specialist diaphragm wall grab must be checked against the actual bite geometry, rotation, jaw opening and excavation cycle.
Panel width also affects reinforcement handling, cage dimensions, tremie access, joint placement and concrete volume. Those requirements can govern practical output more than the nominal maximum grab dimension.
Water, Slurry and Joint Constraints
Before diaphragm wall grabs start excavation, the slurry pump must be fully submerged in bentonite slurry [S4]. The open trench depends on slurry support to limit groundwater entry and prevent collapse of the exposed soil [S5].
Guide walls provide temporary support for the upper soil, maintain horizontal alignment and wall continuity, and guide the grab vertically [S4].
For procurement, specify the joint type, guide-wall geometry, slurry plant requirements and cleaning cycle rather than treating a panel width and depth rating as a complete operating specification.
Equipment Sizing Checklist for Buyers
Require the supplier to identify maximum grab width, maximum trench length, rated excavation depth and the crane configuration supporting those values. Bauer DHG V data provides a concrete benchmark of 1,500 mm width by 3,800 mm length [S5], while Casagrande provides a separate 1,500 mm by 4,000 mm maximum [S2].
Confirm whether quoted dimensions describe one excavation bite, a multi-bite finished panel, or the finished wall thickness. Keller’s standard thicknesses of 32, 36, 42, 48 and 60 in, equivalent to approximately 813, 914, 1,067, 1,219 and 1,524 mm, describe the finished wall thickness [S1].
Check operating weight against the rotary drilling rig or crawler-crane class selected for deep excavation, and size the support system for the measured panel reaction. Verticality and alignment should be verified at the final panel depth, not merely at guide-wall level [S4].
For a conventional grab rig, establish the panel length envelope from the cited equipment information and then establish depth from the crane and grab combination [S2][S3]. The 10–75 m depth range published for specific crawler-crane and grab combinations is a wider market envelope, not a guarantee for every machine [S6].
The next procurement checkpoint is the supplier’s dimensioned panel layout showing bite width, finished panel width, vertical length, maximum depth, joint type, crane model and operating-weight distribution. That drawing resolves the terms that cannot be compared safely across a 1,500 mm grab rating, a 1,800 mm panel width and a 4,200 mm finished panel width.