The diaphragm wall panel is a core element of modern excavation enclosures and cut-off walls in special foundation engineering. Each panel forms an individual wall segment of a cast-in-place diaphragm wall and takes on tasks in excavation support, water sealing, and load transfer. Over a structure’s life cycle, it may become necessary to adapt, open, or deconstruct a panel—for example for openings, connections, or partial deconstruction. Quiet, low-vibration methods are then used, in which tools such as Darda concrete crushers or rock and concrete splitters from Darda GmbH can play an important role depending on the boundary conditions.
Definition: What is meant by diaphragm wall panel
A diaphragm wall panel is a single cast-in-place concrete panel produced in a trench stabilized with supporting fluid (usually bentonite or polymer slurry). Several panels are connected via joints in sequence to form the continuous diaphragm wall. Typical features include the sequence of primary and secondary panels, installation of reinforcement cages, the use of sealing and construction joints, and concreting via tremie pipes (tremie method). The panel resists earth pressure, water pressure, and temporary construction-stage loads; in combination with anchors, bracing, or slabs, it functions as part of the shoring.
Construction and design details of diaphragm wall panels
Execution begins with guide walls, followed by excavation of the trench using a grab or cutter under supporting fluid. Stop-end elements (e.g., joint pipes or steel sheet profiles) form end faces and joints. The reinforcement cage is then positioned and concreted via tremie pipe, displacing and recovering the supporting fluid. Decisive design aspects include geometry (wall thickness, depth), verticality, joint tightness, concrete quality, as well as the formation of the capping beam with subsequent head trimming. Depending on the project, sealing systems such as waterstops, injection hoses, or swelling elements are provided to keep panel joints permanently watertight.
Construction sequence in steps
- Construct guide walls as alignment and support for equipment.
- Excavate the trench under supporting fluid down to competent strata.
- Install stop-end elements and perform control measurements (depth, verticality).
- Lower the reinforcement cage with spacers and any embedded items.
- Concreting by the tremie method; controlled displacement of the supporting fluid.
- Curing, exposing, and subsequent head trimming for load transfer.
Primary and secondary panels
Primary panels are constructed with stop-ends on both sides; they define the geometry. Secondary panels are concreted in between and interlock with the primary panels. The joints are executed as construction and sealing joints. The composite action ensures the stability and watertightness of the entire diaphragm wall.
Reinforcement, joints and watertightness
The reinforcement is designed according to earth and water pressure, construction-stage loads, and use. One- or two-layer mesh and bar reinforcement is frequently used, locally strengthened at openings, anchor levels, and in areas with transverse loads. Joints are formed as panel joints and are supplemented with joint profiles, waterstops, or injection hoses. For highly stressed or water-loaded structures, small crack widths, adequate cover, and a suitable concrete mix design are key parameters for durability.
Types of joints and sealing systems
- Construction joints between panels with joint sheets or joint pipes.
- Sealing joints with internal waterstops or swelling profiles.
- Injection joints with subsequent injection capability for defect remediation.
Dimensions, tolerances and quality assurance
Typical panel thicknesses range from about 0.6 to 1.5 m, depths often between 20 and 80 m, and significantly more depending on the project. Common requirements concern verticality, flatness, and integrity. Quality assurance includes measurements of trench depth, density/viscosity of the supporting fluid, fresh and hardened concrete tests, as well as integrity testing. Execution and verification follow recognized engineering rules and the applicable standards and guidelines.
Testing and documentation
- Control of supporting fluid and trench geometry.
- Concrete testing (consistency, compressive strength, temperature control).
- Integrity verification (e.g., low-impact) and joint testing.
- Documentation of concrete volumes, slurry return flow, and installation times.
Deconstruction, openings and adaptations to diaphragm wall panels
During construction or in service, panels are often worked locally: openings for utilities, temporary breakthroughs, adaptations at anchor levels, or trimming of panel heads. Controlled, low-vibration methods take priority to avoid endangering adjacent structures, joint seals, and serviceability. Depending on geometry, reinforcement ratio, and surroundings, mechanical breaking, splitting, milling, or sawing are used; in sensitive environments, portable hydraulic tools with high precision and low emissions are advantageous.
Tools and methods in practice
- Concrete crushers from Darda GmbH enable stepwise, controlled removal of concrete in confined spaces, e.g., for edge-near openings. Low vibration protects joints and seals.
- Rock and concrete splitters from Darda GmbH act via drilled holes and generate defined crack patterns in massive concrete members. They are suitable for gently opening or segmenting thick panels with high reinforcement ratios.
- Steel shears and combination shears from Darda GmbH cut reinforcing bars, anchor heads, or embedded parts efficiently without causing unnecessary collateral damage to the concrete.
- Hydraulic power units from Darda GmbH reliably supply mobile tools, which is advantageous in tight excavations and under limited power supply.
- Multi Cutters offer flexibility for mixed tasks when concrete and steel must be cut in quick succession; with complex panel openings this can consolidate work steps.
Application areas related to diaphragm wall panels
Diaphragm walls are used in urban excavations, at deep stations, in cut-and-cover tunneling, and for groundwater control. Work on panels touches several application fields of Darda GmbH:
- Concrete demolition and special deconstruction: Local removal of panel heads, elimination of defects, selective removal for construction stages.
- Strip-out and cutting: Creating service openings, recesses, and penetrations; often with concrete crushers and steel shears.
- Rock demolition and tunnel construction: In top-down construction or excavations near rock, transitions between rock support and diaphragm wall are worked; rock and concrete splitters are particularly suitable here.
- Natural stone extraction and special applications: Know-how from controlled splitting can be transferred to massive concrete sections where low emissions are required.
Occupational safety, vibrations and environmental aspects
Work on diaphragm wall panels requires a coordinated safety concept. This includes stable construction stages, fall protection, load redistribution, and protection of third-party structures. Methods with low vibrations, reduced noise, and minimized dust generation are advantageous in sensitive locations. Hydraulic, portable systems support low-emission execution. Information on protective measures, permits, and disposal must always be checked on a project-specific basis and is fundamentally non-binding and general.
Targeted reduction of emissions
- Segmental removal with concrete crushers instead of percussive methods reduces vibrations.
- Splitting via drilled holes limits crack propagation and reduces noise.
- Mist spraying or wet cutting binds dust; retention of flushing water and slurries protects water bodies.
Planning and interfaces
Before intervening in a diaphragm wall panel, structural verification, construction-stage analyses, and rebar detection are required. Coordination between structural design, geotechnical engineering, and execution defines sequences for bracing, load redistribution, and joint compatibility. Clear logistics for debris pieces, rebar remnants, and the service routing of the hydraulic power packs increases process reliability.
Temporary support and construction stages
Opening a panel creates new load paths. Temporary bracing before the first cut, a defined cutting pattern, and a staged sequence with monitoring prevent unintended crack formation. Rock and concrete splitters offer high control over crack initiation, while steel shears handle exposure and trimming of reinforcement.
Typical defects and remediation strategies
Frequent findings include honeycombing, local voids, insufficient joint tightness, or excess concrete at the head that must be milled out. Remediation is performed using reprofiling concretes, injections, or selective removal of damaged zones. For local removal, concrete crushers and splitting methods are practical because they protect adjacent sealing joints and built-in components and preserve the integrity of neighboring panels.
Practice-oriented checklist for work on diaphragm wall panels
- Review existing documents, as-built data, and joint locations; perform rebar scanning.
- Verify stability, construction stages, and temporary bracing.
- Select the method: concrete crusher for precise removal, splitters for massive sections, steel shears for reinforcement.
- Define cutting and splitting pattern; plan the drilling pattern; protect adjacent joints.
- Organize hydraulic supply and logistics (access, load handling, disposal).
- Manage emissions: dust control, noise protection, ground vibration monitoring.
- Document execution; follow up with integrity and watertightness tests.