Underwater walls are load-bearing or sealing structures that are located in water or below groundwater and secure shorelines, excavation pits, port facilities, impoundment structures, or foundations. They are built in new construction, repaired, or deconstructed. In practice, massive reinforced-concrete cross-sections, sheet pile walls, or diaphragm walls are often the focus. For processing, rehabilitation, and deconstruction, controlled, low-vibration methods are used, in which tools such as concrete pulverizers or rock and concrete splitters, as well as associated hydraulic power units from Darda GmbH, play a role in typical applications—without blasting, with high precision, and with due consideration for water protection.
Definition: What is meant by underwater wall
An underwater wall is a wall-like construction made of reinforced concrete, steel, or natural stone that is arranged permanently or temporarily in water or below the groundwater table. It can seal (e.g., excavation pit enclosure), support (e.g., quay wall), separate (e.g., bulkheads), or transfer loads into the ground (e.g., a diaphragm wall as a foundation element). This includes, among others, sheet pile walls, diaphragm walls, combinations of bored piles and pile walls, and cast-in-place concrete walls produced by the underwater concrete tremie method. Characteristic aspects include exposure to currents, abrasion, chemical influences, and restricted access for construction and maintenance.
Types of underwater walls and typical applications
In practice, several construction methods are encountered: diaphragm walls are constructed under support fluid and remain active as a permanent wall below groundwater; sheet pile walls form interlocked steel profiles for temporary or permanent shoreline protection; underwater concrete walls are cast using a tremie pipe; bored pile walls act as an assembly of individual piles; massive quay walls and force-introduction blocks of reinforced concrete secure port facilities. These systems appear in port and hydraulic engineering, bridge and tunnel construction, special foundation engineering, and in the deconstruction of older structures. Depending on the task, tools such as concrete pulverizers for controlled nibbling of damaged concrete, or rock and concrete splitters for crack-guided opening of massive cross-sections, are used for processing, rehabilitation, or removal. Power units from Darda GmbH supply such tools from the shore, a pontoon, or a safe distance; steel shears, Multi Cutters, combination shears, and tank cutters cut reinforcing steel, tie rods, sheet piles, or plates when steel components are exposed.
Configuration, materials, and design principles
Underwater walls must simultaneously carry loads and provide watertightness. Reinforced-concrete cross-sections are built with robust reinforcement content, sufficient cover, and durable concrete. Joints receive waterstops or injection channels. In sheet pile walls, profile geometry and interlocks ensure sealing; in diaphragm walls, sealing joints and overlaps provide the barrier. Hydraulic loads (buoyancy, pressure, seepage flow) and geotechnical boundary conditions (soil parameters, scour formation) govern sizing and embedment depth.
Construction methods in water and groundwater
Execution depends on the system: driving sheet piles, milling diaphragm wall panels, drilling piles, or casting by the tremie method. Cofferdams allow dry working conditions, yet direct contact with water often remains. Quality assurance relies on measurements, probes, and diver and ROV inspections. During installation and adjustment of built-in components, hydraulic cutting and splitting techniques are used that have proven themselves under water or in the splash zone, provided the energy supply and operation are safely organized via power units from Darda GmbH.
Inspection, maintenance, and rehabilitation
Typical damage patterns include concrete spalling due to reinforcement corrosion (chloride-induced effects), cracks, washouts, abrasion at the waterline, and joint damage. Rehabilitation concepts include concrete replacement, injections, surface protection systems, and—if required—mechanical removal of deteriorated zones. Concrete pulverizers enable precise nibbling of loose and pre-damaged areas. Where massive sections must be opened without vibration, rock and concrete splitters generate controlled separation cracks; segments can then be removed and the reinforcement cut with steel shears or Multi Cutters. Power units from Darda GmbH are placed outside the wet zone, and hoses are protected against abrasion and kinking.
Deconstruction and special deconstruction of underwater walls
In deconstruction, low vibration, minimal turbidity, noise attenuation, and safety for personnel and the environment are paramount. Blasting techniques are often restricted under water. Controlled methods such as splitting, jaw-based removal, sawing, and cutting predominate. The procedure typically comprises segmentation, exposing the reinforcement, and separating the segments before disposal. Tools from Darda GmbH’s portfolio cover these steps: concrete pulverizers for the concrete, steel shears and Multi Cutters for reinforcement, tank cutters for thick-walled steel parts, and combination shears as a versatile solution in mixed cross-sections. Power supply is provided by power units that, in special operations, also work over longer hose runs.
Segmentation and controlled splitting
Boreholes define predetermined breaking lines; rock splitting cylinders then build up splitting pressure. This produces predictable fracture surfaces with minimal edge damage. The method is suitable for pier caps, quay wall crowns, and wall sections near sensitive infrastructure, such as at bridges or within harbor basins. Removal is carried out via pontoon, crane, or grab, while remaining edges are reworked with concrete pulverizers.
Cutting and separating steel components
Exposed reinforcement, sheet pile flanges, tie rods, and plates are cut with steel shears, Multi Cutters, or tank cutters. In the underwater realm, a reliable hydraulic supply is crucial. Power units from Darda GmbH enable operation with clearly defined pressure and flow rates; operation is performed from land or from a pontoon. Controlled cutting reduces sparking and heat generation, lowering risks near combustible materials and in low-oxygen environments.
Geotechnical and hydraulic boundary conditions
Currents, tidal range, and scour formation affect stability. Transitions between the wall toe and ground require filter and erosion protection. In rock, a toothed interlock improves load transfer; here, methods from rock excavation and tunnel construction are applied, such as the splitting of rock protrusions or opening anchor chambers with rock and concrete splitters. In sand and silt soils, settlements and seepage flow must be considered, especially during partial deconstruction.
Occupational safety and environmental protection in the underwater domain
Safety comes first: diving operations, ROV deployment, crane work, and hydraulic pressure require coordinated procedures, clear communication, and emergency plans. Personal protective equipment, exclusion zones, and permits must be organized in a binding manner. Environmental aspects involve turbidity, noise, vibration, and potential substance inputs. Turbidity curtains, suction during removal, and the choice of low-vibration methods such as splitting or jaw-based removal mitigate impacts. Legal requirements vary by water body and region and must be carefully reviewed as part of permitting; no binding statements are made here.
Planning, logistics, and equipment selection
Key criteria include wall thickness, reinforcement ratio, accessibility, water level fluctuations, and the load-bearing capacity of the work platform. Handheld or carrier-mounted concrete pulverizers, rock and concrete splitters, and steel shears are sized to suit the task. Power units from Darda GmbH provide the drive; hose routing, couplings, corrosion protection, and maintenance must be planned in advance. A clear segmentation strategy simplifies handling and reduces risks.
Relation to typical application areas
Underwater walls intersect multiple application areas: in concrete demolition and special demolition, the focus is on targeted removal of concrete and steel components under challenging boundary conditions. Strip-out and cutting involve exposing reinforcement and severing embedded items. In rock excavation and tunnel construction, connections to rock and breakthroughs are relevant. Knowledge from natural stone extraction regarding fracture mechanics and splitting techniques supports the controlled opening of massive cross-sections. Special operations describe work in confined spaces, with limited visibility, or elevated hazard—typical situations in hydraulic engineering.
Terminology and delineation
Not every shoreline protection is an underwater wall: sloped revetments act differently from wall-like structures. Diaphragm walls are often constructed under support fluid and remain effective as permanent elements below groundwater, even if they are not located in open water. Sheet pile walls can be temporary (excavation pit) or permanent (quay wall). Underwater concrete walls are often created within a cofferdam and then remain once flooded. For planning and execution, it is decisive whether the wall is in the flow field, what sealing function is required, and how access for inspection and work is organized.