Immersion method plays a central role in structural hydraulic engineering, in the deconstruction of water-contact structures, and in operations in flooded structures. Whenever concrete, reinforced concrete, natural stone, or steel components must be worked on below the waterline, professional diving operations intersect with hydraulic demolition and cutting technology. Within this field, methods can be selected and combined so that work is carried out safely, precisely, and with minimal impact on the surroundings. Product groups from Darda GmbH such as rock and concrete splitters, concrete demolition shears, power units, combi shears, multi cutters, steel shears, and tank cutters are used in practice in a context-specific way, provided the conditions for underwater deployment are met.
Definition: What is meant by immersion method
Immersion method denotes the entirety of methods by which professional divers and remotely operated systems (ROV) plan and execute underwater work. This refers to work-related diving operations in construction, deconstruction, and maintenance—not sporting activities. It includes the provision of breathing gas (for example, surface-supplied), the choice of diving mode (such as helmet diving, saturation diving, SCUBA in shallow water), work organization under elevated ambient pressure, and the coordinated use of tools for drilling, splitting, cutting, crushing, and recovery. The aim is a safe, controlled approach in media with restricted visibility, current, cold, and distinctive acoustic conditions.
Types of diving and work methods in construction and deconstruction
Types of diving and work methods depend on depth, duration, accessibility, and the task at hand. In the construction and deconstruction context, the following approaches have become established and can be combined with hydraulic demolition technology when supply, control, and safety are ensured:
Surface-supplied operations (helmet diving)
In surface-supplied diving, crews receive breathing gas, communications, and often power through an umbilical. The method is common in heavy underwater operations because it provides stable working conditions, clear lines of command, and the ability to use powerful hydraulic tools. It is applied on pile heads, quay walls, weirs, bridge piers, and lock components.
Saturation diving
For long deployments at greater depths, the body is “saturated” to an elevated ambient pressure to reduce decompression times. In civil deconstruction this is rare but may be required at deep intakes, tunnel portals, or offshore components. Tool handling and logistics are highly standardized here, with process safety taking precedence.
SCUBA in shallow water
Open-circuit SCUBA is mainly used for inspection, surveying, marking, and lighter auxiliary tasks. For extensive removal work and high-power applications, surface-supplied methods or working platforms are generally preferred.
Typical underwater work steps
- Surveying, exposure, and securing of the work site (visual markers, guide buoys, shoring).
- Mechanical processing: drilling, splitting, crushing, cutting, and suction removal of material.
- Debris clearance and documentation via video, photo, or acoustic methods.
Fields of application: underwater construction, concrete demolition, and special deconstruction
The combination of immersion method and hydraulic demolition technology becomes relevant wherever components are in or under water. These include bridge piers and pier caps, quay walls, quay piles, sheet pile walls, impoundment structures, outfall and siphon culvert structures, tunnel portals, foundation remnants, and flooded basement and tank areas. In these environments, methods can be structured to achieve the targets of safety, precision, emissions reduction, and schedule adherence.
Concrete demolition and special deconstruction
With reinforced concrete under water, a step-by-step approach has proven effective: rock and concrete splitters are used first to pre-fracture the cross-section with low stress, after which concrete demolition shears can selectively crush the concrete. Exposed reinforcement can be cut with steel shears or multi cutters. This interplay reduces vibration and shock waves, which is advantageous in the sensitive water environment.
Strip-out and cutting
In flooded structures or tanks, strip-out requires calm, low-spark methods. Where structurally appropriate, tank cutters, steel shears, combi shears, and multi cutters are used. Cutting is performed section by section, assisted by slings and lifting gear to recover components in a controlled manner.
Rock demolition and tunnel construction
In underwater rock demolition, drilling patterns and rock splitting cylinders support controlled detachment of rock. In tunnel structures and intake structures, execution and safeguarding are closely coordinated with flow protection, sediment management, and visibility improvement (for example, pre-suction).
Natural stone extraction
Below the waterline, natural stone beds can be separated block by block using splitting technology, as in natural stone quarrying. The low vibration protects existing structures and the surroundings; flow and turbidity management are integral parts of planning.
Special operations
After flood events, in accidents, or in contaminated areas, immersion method is combined with hydraulic technology to remove damaged components in a controlled manner, create openings, or install temporary stabilizations. In the presence of particular hazards, remotely operated systems can be prioritized.
Technical interfaces: safely operating hydraulics under water
For hydraulic tools to work reliably under water, media supply, sealing systems, and control must be tailored to the operating environment. In practice, hydraulic power units are often operated at the surface; power transmission takes place via suitable high-pressure hoses and couplings with corrosion protection. The following points are key:
- Energy and media supply: selection of flow rates, pressure stages, oil temperature control, and filtration.
- Hose and load management: routing, buoyancy compensation, chafe protection, and bend radii.
- Control and communication: clearly defined hand signals, voice communication, and emergency procedures.
- Material and corrosion protection: protective caps, greases, flushing processes, and appropriate storage after use.
- Environmental aspects: leak minimization, containment and suction concepts, and sediment retention.
Process chain: from site measurement to execution
Structured workflows reduce risks and increase quality. A proven roadmap includes:
- Exploration: structure analysis, line detection, and assessments of flow and visibility.
- Permits and protective measures: definition of exclusion zones, sediment and noise protection.
- Method selection: alignment of diving mode, work windows, and tool strategy.
- Tool and accessory selection: concrete demolition shears, rock and concrete splitters, steel shears, combi shears, multi cutters, tank cutters, and suitable power units.
- Trial step: test at a representative location to fine-tune drilling pattern, splitting sequences, and cut edges.
- Execution: sectional work with interim control and documented release.
- Documentation: video/photo evidence, measurement records, material removal, and water body condition.
Safety and health protection in diving operations
Safety takes precedence. The applicable rules of occupational safety and health apply. The following aspects are generally to be considered, without this being an exhaustive or binding list:
- Risk assessment focusing on differential pressure, current, visibility, cold, and potential contamination.
- Authorization and isolation procedures, clear responsibilities, and redundant rescue means.
- Decompression management and medical precautions for diving operations.
- Safe handling of tools, protection against pinch and cut hazards, load handling, and signaling.
Tool selection in interplay with immersion method
Tool choice follows the component, its location, and the desired removal mechanism. Concrete demolition shears are helpful for selective crushing of reinforced concrete under water, especially after prior stress relief by splitting technology. Rock and concrete splitters enable controlled opening of cross-sections with low vibration input. For exposed metals, steel shears or multi cutters are suitable; tank cutters and combi shears cover more complex geometries. Power units supply the tools from a safe distance. The combination of several steps—drilling, splitting, crushing, cutting, clearing—has proven effective.
Example process variants
- Pile head under water: set drilling pattern – split with rock splitting cylinder – crush with concrete demolition shear – cut reinforcement – clear debris.
- Quay wall refurbishment: sectional concrete removal with concrete demolition shear – relief via splitting technology – trimming and free cuts with steel shear/multi cutter.
- Rock spur at the intake: core drilling – controlled splitting – piecewise removal and transport.
Quality assurance and evidence
Under water, quality assurance is achieved through defined tolerances, documented cut and split lines, visual and acoustic checks, and test specimens on exposed surfaces. Additionally, sonar, video, and photo recordings help to transparently document processing progress.
Ecological and organizational aspects
Turbidity and sediment management, protection of aquatic habitats, noise reduction, and economical use of energy are integral components. Methods with low vibration and emission levels—such as splitting and targeted crushing—support these goals. Organizationally, clear procedures, qualified personnel, and coordinated provision of equipment ensure execution.