Diaphragm wall cutter

The diaphragm wall cutter is a specialized construction machine for the precise excavation of deep, narrow trenches under support fluid. It is primarily used in dense inner-city areas and in special foundation engineering when low vibration, exact verticality, and high trench quality are required. In numerous projects, the tasks involved in diaphragm wall construction intersect with concrete demolition and special demolition: Openings, connections, and later adjustments to diaphragm walls are often executed using controlled cutting and splitting methods. In practice, among other tools, concrete pulverizers, rock and concrete splitters, and suitable hydraulic power packs from Darda GmbH are used to detach massive components with low vibration, trim edges cleanly, or separate reinforcement in an orderly manner.

Definition: What is meant by a diaphragm wall cutter

A diaphragm wall cutter is understood to be a hydraulically driven, crane-guided cutter body with two counter-rotating cutter wheel sets that remove soil or rock by cutting. Excavation takes place under support fluid (usually bentonite slurry or polymer slurry), which stabilizes the trench, binds fines, and enables material transport. The cutter is guided section by section (panels), the excavated trench is then fitted with reinforcement cages and filled with concrete. The method is used for cut-off and shoring walls, excavation pit enclosures, foundations, and tunnel connections, and is designed for great depths and high dimensional accuracy.

Function and design

At its core, a diaphragm wall cutter consists of the cutter body (cutter package) with two cutter wheels, a hydraulic drive, weighting and guidance elements, a suspension on the crane or Kelly system, and lines for support fluid and excavation discharge. The rotating cutter wheels loosen soil or rock; the material is removed together with the support fluid via internal channels and separated at the surface. Sensors monitor verticality, torque, feed, and depth. The support fluid is continuously conditioned to ensure trench stability. Thanks to the high specific torque, dense soils and in-situ rock can be processed efficiently.

Areas of application and construction sequence

Diaphragm wall cutters are used wherever deep, narrow, and load-bearing walls with low vibration and high precision are required. Typical applications include excavation pit enclosures for buildings, infrastructure structures, tunnel connections, cut-off walls in hydraulic and port projects, as well as foundation measures in inner-city environments.

Typical construction sequence

• Construction of a guide wall to guide and seal the support fluid at the surface
• Insertion of the cutter, reaching the target depth, continuous cutting under support fluid
• Transport and separation of the excavated material, conditioning of the support fluid
• Lowering the reinforcement cages, concreting the panel using the tremie method
• Repeating panel by panel, executing joint and connection elements

As part of the excavation pit works, cut-off levels are later established and openings for anchors or connections are created. For these follow-up works on massive components, concrete pulverizers or hydraulic wedge splitters are often suitable to define edges, remove head concrete, or create breakthroughs with low vibration—particularly relevant in special demolition and in building gutting and concrete cutting within existing environments.

Support fluids and geotechnics

The quality of the support fluid influences the stability, friction behavior, and cleanliness of the trench. Bentonite slurries offer proven filter cake formation, while polymer slurries often enable lower sludge production and facilitate cleaning. Important parameters are density, viscosity, sand content, and gel strength. Geologically varying layers, groundwater levels, and obstacles (e.g., boulders, old foundations) determine the choice of tools (chisels, picks, cutter wheels) and the operating strategy (speed, feed, flushing volume).

Precision, tolerances, and quality assurance

For the serviceability of the diaphragm wall, verticality, trench width, panel straightness, and the quality of contact joints are decisive. Modern systems record tilt and depth in real time. Quality assurance includes measurements at the guide wall, testing of the support fluid, sediment checks at the trench bottom, and documentation of concreting. Clean edges and defined connection surfaces facilitate later breakthroughs or the connection of slabs. When the head area is brought to cut-off level after earth excavation, concrete pulverizers can be used for controlled demolition and exposing the reinforcement; for particularly massive wall heads, hydraulic wedge splitters are a low-vibration option.

Interfaces with demolition and cutting technology

The construction of diaphragm walls is often closely related to subsequent cutting and deconstruction works:

• Removal of wall head concrete: After the excavation pit is dug, the wall head is cut down to the final elevation. Concrete pulverizers enable targeted detachment of concrete with low vibration, and the exposed reinforcement can then be cut with steel shear.
• Openings and connections: Defined recesses must be created for anchors, service routes, or door/tunnel breakthroughs. In thick wall sections, hydraulic wedge splitters help initiate controlled cracks; for remaining sections, hydraulic shear or Multi Cutters may be used.
• Deconstruction of temporary elements: Guide walls, auxiliary foundations, and inserts are efficiently deconstructed with concrete pulverizers and suitable hydraulic power packs.

In rocky areas or in rock excavation and tunnel construction, the cutter may encounter obstacles. Exposing or pre-splitting such zones with hydraulic wedge splitters supports cutting progress without subjecting sensitive neighboring structures to vibration. In special operations (e.g., confined inner-city sites, protection of historic buildings), this combination is often advantageous.

Performance parameters and selection criteria

The following key values are in focus when selecting a diaphragm wall cutter:

• Trench width and depth: Typical widths are in the range of 600–1500 mm; depths of 50–100+ m depend on geology, crane capacity, and support fluid management.
• Torque and power: High torques ensure progress in dense soils and rock; the hydraulic supply must be stable and powerful.
• Verticality control: Precise sensors and control reduce correction runs and improve the quality of panel joints.
• Conveying and separation system: Efficient slurry handling, screening, and desanding/desilting are crucial for economy and quality.
• Crane and logistics: Load capacity, hook height, hose and power routing, site layout, and delivery logistics determine feasibility.

Appropriate attachments must be considered for accompanying and follow-up works on the wall. Hydraulic power packs from Darda GmbH provide the necessary energy for concrete pulverizers, hydraulic wedge splitters, or steel shear and ensure consistent performance in confined spaces.

Operation, maintenance, and typical faults

Reliable operation requires trained personnel, orderly construction logistics, and careful maintenance. Wear parts on cutter wheels and seals must be renewed early. Faults may manifest as increased torque, reduced conveying performance, or decreasing verticality. Countermeasures range from adjusting the support fluid to changing tools to temporarily modifying the operating strategy. A clean separation chain minimizes sediment deposits in the trench and reduces the risk of incidents.

Occupational safety and environmental protection

Safety and environmental protection have high priority. Relevant aspects include handling of the support fluid, securing the guide wall areas, controlling emissions (noise, fine dust), and safe lifting and rigging. For follow-up works on the diaphragm wall, concrete pulverizers and hydraulic wedge splitters support a low-vibration approach. Information on occupational safety must always be assessed project- and country-specifically; binding requirements result from the relevant standards and permits.

Alternatives and differentiation

As an alternative to the diaphragm wall cutter, diaphragm wall grabs (mechanical excavation under support fluid) may be suitable, particularly in softer soils or with lower verticality requirements. For excavation pit enclosures, pile walls (bored piles, secant pile wall) or mixed-in-place methods are also options. The choice of system depends on geology, space constraints, permissible vibrations, required tightness, and planning objectives.

Planning and interface coordination

Successful execution requires close coordination between designers, site management, special foundation engineering, and deconstruction trades. Key points include defining panel lengths, the joint and sealing concept, reinforcement cage geometry, the concrete mix design, and later accessibility for follow-up works. Where openings, anchors, or penetrations are planned, these should be coordinated early with the planned cutting and splitting technology (e.g., concrete pulverizers, hydraulic wedge splitters) to minimize additional interventions.

Practice-oriented execution hints

1. Construct the guide wall precisely to support verticality and tightness.
2. Continuously test the support fluid (density, viscosity, sand content) and document the results.
3. Match tool selection to geology; change chisels and picks in hard zones in good time.
4. Size the separation plant with sufficient capacity to ensure consistent quality.
5. Plan follow-up works early: Wall head concrete and openings can be produced with low vibration using concrete pulverizers and hydraulic wedge splitters.
6. Plan rebar cuts in an orderly manner; feed steel shear or hydraulic shear cleanly.

Application-related references

In concrete demolition and special demolition, work often focuses on selective detachment and separation on existing diaphragm walls, for example when tying in new structural components. Building gutting and concrete cutting requires defined openings and edges—this is where controlled splitting and pulverizer methods excel. In rock excavation and tunnel construction, diaphragm walls meet changing rock conditions; preparatory splitting techniques can accelerate cutting. In natural stone extraction, the diaphragm wall cutter has no direct role; however, knowledge of splitting behavior and rock mechanics is useful for adjacent work. Special operations such as work in sensitive neighborhoods benefit from low-vibration methods.

Digital support and documentation

Modern diaphragm wall cutters record process data on inclination, depth, torque, and circulation flows. The evaluation supports quality assurance, facilitates proof of compliance, and improves coordination with adjacent trades. Structured documentation of support fluid parameters and concreting is just as important as the logged execution of follow-up works with concrete pulverizers or rock wedge splitters to keep structural integrity traceable.