An entry shaft is the controlled access point to underground structures—from sewerage and utility infrastructure to underground car parks and bunkers through to tunnel construction. It serves construction progress, inspection, maintenance, and deconstruction. In planning and execution, structural safety, watertightness, accessibility, and emission control take priority. In concrete demolition, during refurbishment or enlargement of a shaft, low-vibration, low-impact methods are often used, such as low-noise concrete crushers and rock and concrete splitters from Darda GmbH.
Definition: What is meant by entry shaft
An entry shaft (also called access shaft or shaft structure) is typically a vertical, less commonly inclined opening from the surface to a lower-lying void. It enables the access of personnel, tools, and materials, ventilation, and—depending on use—the installation of components such as ladders, rungs, pipelines, or cables. Entry shafts are built as cast-in-place concrete structures, from precast shaft rings, or as a supported rock/soil shaft with lining (for example shotcrete). They often terminate in a load-bearing shaft cover with a manhole cover or a shaft head frame.
Configuration, function, and typical construction types
The configuration is determined by purpose, depth, geometry, the subsoil, and the groundwater level. Cylindrical or rectangular cross-sections are common, consisting of the shaft invert (base), wall, and cover. Load-bearing materials include reinforced concrete, reinforced shotcrete, polymer concrete, or—for temporary shafts—steel sheet piles or shoring elements. In utility and sewer shafts, an invert channel is formed; in tunnel and launch shafts, lifting, conveying, and ventilation functions dominate. Sealing is provided by waterstops, sealing profiles, injection hoses, and mineral coatings.
Use in tunnel construction and underground structures
In rock excavation and tunnel construction, the entry shaft performs key tasks for site logistics: it serves as a launch or reception shaft, as a supply shaft for materials and power, and as an escape and ventilation shaft. During fit-out, components such as support frames, shaft fixtures, and anchor points are added. In urban environments, low noise and vibration levels are important to protect adjacent buildings.
Launch, reception, and service shafts
Launch shafts accommodate tunnelling machines, conveying equipment, and bracing. Reception shafts enable the exit of the drive and the removal of temporary installations. Service shafts allow permanent inspection and maintenance. In all cases, safe access, defined workstations, segregation of hazard zones, and reliable ventilation are required.
Role in concrete demolition and specialized deconstruction
When adapting, refurbishing, or deconstructing an entry shaft—such as enlarging the opening, replacing the shaft cover, or removing damaged concrete areas—controlled removal methods are crucial. In confined shafts, the use of hydraulic handheld tools enables targeted, edge- and structure-friendly work. Typical tasks in concrete demolition and specialized deconstruction include:
- Removal of the shaft head and cover bearing without damaging adjacent structures
- Selective deconstruction of shaft rings, cast-in-place walls, and fillets
- Extraction of core samples, exposing and cutting reinforcement
- Creating openings for new pipelines or shafts
- Knocking off loose concrete and removing corroded installations
Tool selection and methods in confined shafts
The choice of method depends on component thickness, reinforcement density, accessibility, and requirements for vibration, noise, and dust. In entry shafts, compact hydraulic tools supplied by externally positioned hydraulic power packs are advantageous:
- Concrete crushers: For low-noise, low-vibration removal of reinforced concrete elements, e.g., at the shaft head, wall areas, and opening edges. They crush the concrete; reinforcement is then cut with steel shears or Multi Cutters.
- Rock and concrete splitters with rock splitting cylinders: For controlled splitting of massive concrete or natural stone areas, e.g., when deconstructing thick cast-in-place walls or enlarging openings. This method acts with low vibration into the component cross-section.
- Combination shears and steel shears: For rapid cutting of installations, structural steel, guardrails, or heavily reinforced zones.
- Concrete crushers in combination with saw cuts: Pre-cutting with a floor saw or wire saw (where accessible), followed by biting off remaining areas with the crusher for clean edges.
Refurbishment, extension, and repurposing
Damage to entry shafts appears as cracks, spalling, leaks, delamination of coatings, or corrosion on installations. Refurbishment involves injecting leaky joints, removing damaged areas, and rebuilding them. For extensions—e.g., larger pipe diameters or new superstructures—small, controlled work steps can be combined with concrete crushers and rock and concrete splitters. This protects adjacent structures, utilities, and surfaces. In existing structures, documenting the residual load-bearing capacity and the temporary shoring is crucial.
Occupational safety, access, and safe procedures
Work in an entry shaft is often considered work in confined spaces. It requires coordinated safeguarding: access control, fall protection, gas clearance testing, ventilation, lighting, and a rescue plan. The following steps have proven to be a structured sequence:
- Hazard analysis, work-area release, and barricading of the surface
- Ventilation and gas testing, establishing work positions and anchor points
- Defining transport interfaces and lifting points for tools, power packs, and materials
- Stepwise removal with continuous monitoring of component condition and surroundings
- Material separation, haulage, cleaning, and final leakage and visual testing
Legal and normative requirements vary by country, region, and intended use. They must be verified on site and integrated into work planning.
Subsoil, water, and sealing
The transition between the shaft structure and the subsoil is sensitive from a building physics perspective. Groundwater, variable loads, and settlements stress joints and connections. During deconstruction or when creating openings, seals must be secured temporarily and renewed permanently. Intruding water can impair visibility and tool safety; conveying equipment and pump sumps must be dimensioned accordingly. For durability, suitable sealing systems, sufficient cover, and careful joint design are decisive.
Logistics and power supply in the shaft
Short, safe routes and defined load paths are essential in a confined shaft. Hydraulic power packs are preferably placed outside the shaft to keep exhaust, noise, and heat out of the interior. Power feeds (hydraulic hoses, power cables) must be protected against crushing and sharp edges. Crushed material is recovered in stages; this reduces loads, lowers lifting risks, and improves oversight. Clearly delineated surface areas are suitable for temporary storage.
Material separation, emissions, and sustainability
Clean separation of concrete, reinforcing steel, and installations facilitates recycling and disposal. Low-vibration methods—such as splitting with rock and concrete splitters or biting with concrete crushers—reduce vibration, noise, and dust. Water mist systems and localized extraction improve air quality in the shaft. In special operations such as work in sensitive environments (hospitals, laboratories, heritage structures), particularly quiet and controlled methods should be preferred.
Planning and quality assurance
Robust planning considers load paths, dimensions, access, ventilation, lighting, rescue routes, and interfaces to adjacent structures. Before starting, review as-built documentation, locate utilities, and set monitoring points for deformation control. During execution, document removal steps and monitor the component behavior. For completion, leakage and visual tests as well as an updated survey are advisable—especially for later repurposing or long-term maintenance planning.
Practical examples from application areas
In concrete demolition and specialized deconstruction, the shaft head can be pre-cut into segments and removed with concrete crushers; reinforcement is cut with steel shears. In strip-out and cutting, new cable penetrations in the shaft are created by core drilling followed by edge finishing. In rock excavation and tunnel construction, rock and concrete splitters can be used to widen rocky shaft wall areas in a controlled manner. In natural stone extraction, access shafts serve as entries to drifts; splitting enables low-vibration extraction. In special operations within explosion-hazard areas, low-spark methods and appropriate tool selection are essential.