An access shaft is the vertical backbone of many structures and pieces of infrastructure: it routes utilities, enables access, and connects levels—both in building construction and in rock demolition and tunnel construction. During conversion, strip-out, concrete demolition, or shaft sinking in rock, the access shaft is at the center of technical, structural, and safety-related decisions. Tools such as concrete pulverizers and rock and concrete splitters from Darda GmbH play a central role when low-vibration deconstruction, precise openings, controlled widening, or the safe separation of reinforcement and built-ins are required.
Definition: What is meant by access shaft
An access shaft is understood to be a predominantly vertical shaft that serves to route lines, utilities, and components or ensures access, rescue, and ventilation. In building construction, the access shaft—often also called an installation, supply, or service shaft—is typically made of reinforced concrete, masonry, or lightweight shaft walls and carries risers for potable water, wastewater, heating, cooling, ventilation, as well as cable trays. In mining and tunnel construction, the term describes a walkable or climbable shaft (e.g., as an escape, ventilation, or service shaft) that is created in rock or in shotcrete and segmental lining. What all variants share is the vertical function and the high requirements for fire protection, load-bearing behavior, tightness, maintenance, and safe operation.
Design and types of access shafts
Access shafts are planned and executed differently depending on their use and environment. Construction method, cross-section, and outfitting significantly influence the approach to deconstruction, openings, or strengthening.
Cross-sections, materials, outfitting
- Cross-sections: rectangular for building services shafts; round for precast shafts and in rock construction; polygonal in refurbishment projects.
- Materials: reinforced concrete (cast-in-place or precast), masonry, lightweight shaft walls; in underground construction rock, shotcrete, segmental lining.
- Outfitting: fire protection claddings, installation rails, brackets, inspection openings, firestops and collars at service penetrations.
Structural and fire protection aspects
- Load transfer: shaft walls can be load-bearing, bracing, or non-load-bearing; openings change load paths.
- Fire compartments: firestop elements, collars, and claddings prevent the spread of fire and smoke; changes require coordinated measures.
- Acoustics and vibrations: structure-borne sound decoupling and low-vibration methods are essential in existing buildings.
Built-ins and utility routing
- Lines and routes: water, wastewater, heating/cooling, ventilation ducts, electrical and data cables, some pressurized.
- Anchorages: installation rails, brackets, and penetrations with rebar connections.
- Access: inspection openings, service doors, rungs or ladders in a walkable shaft.
Planning and investigation before interventions
Work on the access shaft begins with safely investigating the existing structure. The goal is to capture load-bearing behavior, utilities, built-ins, and constraints so that interventions proceed in a controlled manner and without collateral damage.
Existing structure assessment
- Review drawings, reinforcement and installation plans; reconcile with site conditions.
- Locating and visual inspection: rebar scanning, remote detection of utilities, camera inspections; gas and pressure tests for media.
- Fire protection status: firestops, fire resistance, claddings, and their condition.
Work and environmental framework
- Component condition and structural analysis: effect of openings, local strengthening, temporary shoring.
- Immission control: dust, noise, vibrations—selection of low-vibration methods.
- Accessibility: confined spaces, vertical work, material logistics, and emergency routes.
Creating openings, enlarging the shaft, and deconstruction
Depending on the objective—inspection openings, shaft enlargement, complete deconstruction—combined cutting and removal methods are used. Priority is given to controlled, low-vibration methods.
Procedure
- Shut down, drain, and secure media; label and verify zero-energy status.
- Preparation: dust suppression, edge relief, temporary safeguards.
- Separation/removal: graded use of concrete pulverizers, rock and concrete splitters, cutting and shearing tools.
- Material separation: separately remove metals, plastics, concrete, masonry.
- Finishing: edge treatment, surface repair, re-establishment of fire protection details.
Tools and methods in the access shaft context
- Concrete pulverizers: for controlled breaking of reinforced concrete walls and slabs in the shaft area; suitable for extracting larger pieces with low vibration, especially in concrete demolition and special demolition.
- Rock and concrete splitters (with rock splitting cylinders): for low-noise, low-vibration widening or splitting; ideal in occupied buildings, with sensitive existing structures, and in special operations.
- Hydraulic power packs: compact power supply for pulverizers, splitting cylinders, and shears; important when working in confined shafts with limited electrical supply; compact hydraulic power units are typically used in such confined conditions.
- Combination shears: cutting reinforcement, light steel sections, sheet metal, and smaller built-ins during strip-out and cutting.
- Multi Cutters: flexible cutting of mixed materials (cable trays, thin-walled pipes, sheets) with varying cross-sections.
- Steel shears: for massive reinforcement, beams, and shaft installations made of steel, e.g., when exposing large utility bundles.
- Tank cutters: relevant at points where shafts run near tanks or plant rooms, e.g., in existing industrial facilities.
Access shafts in rock and tunnel construction
In rock, access shafts serve escape, ventilation, and supply. During sinking and widening, controlled methods offer advantages when blasting vibrations or induced vibrations are undesirable.
Sinking and widening
- Pilot drilling and sectional widening using rock splitting cylinders; targeted crack steering along borehole grids.
- Removing breakout edges with concrete pulverizers on shotcrete lining; gentle removal at connections and anchors.
- Cutting of lining and support elements with steel shears and combination shears.
Safety and logistics in the shaft
- Fall protection, secured load paths, redundant anchorage points.
- Ventilation and gas monitoring; dust and water management.
- Compact hydraulic power packs to supply tools at depth.
Strip-out, utility routing, and material separation
In existing buildings, shafts are often densely occupied. The orderly extraction and separation of materials is crucial for progress, safety, and recycling rates.
Strip-out steps
- Dismantle non-load-bearing claddings and fire protection claddings with regard to reinstatement.
- Selective cutting of cable trays, pipes, and brackets with Multi Cutters and combination shears.
- Free-cutting reinforcement; use steel shears in heavily reinforced areas.
- Remove the load-bearing shaft core with concrete pulverizers or rock and concrete splitters.
Recycling and follow-up work
- Source-separated sorting: concrete/masonry, steel, non-ferrous metals, plastics.
- Edge and surface finishing for subsequent installations.
- Fire-protection reinstatement of firestops after service penetrations.
Occupational safety and protective measures
Safety has priority. The following points are fundamental and should be elaborated for the specific project.
- Safely de-energize, drain, and label media; ensure the absence of pressure.
- Fall and crush protection: guardrails, safety nets, personal protective equipment, remote-controlled working methods where possible.
- Dust and noise reduction: extraction, water mist, low-vibration methods.
- Temporary shoring and edge relief for openings.
- Rescue and communication plan for work in the shaft.
Typical failure patterns and how to avoid them
- Unplanned load redistribution due to openings: assess structurally in advance and proceed in stages.
- Damage to utilities: locate precisely, create pilot openings, expose step by step.
- Transmission of vibrations into sensitive areas: give preference to rock and concrete splitters and concrete pulverizers.
- Insufficient dust management in the vertical shaft: extraction, sealing off levels, plan negative-pressure zones.
Application areas at a glance
Access shaft work touches several application fields of Darda GmbH:
- Concrete demolition and special demolition: deconstruction of shaft walls, openings, edge reinforcements; preferably with concrete pulverizers.
- Strip-out and cutting: removal of built-ins, cutting reinforcement and utilities with combination shears, Multi Cutters, and steel shears.
- Rock demolition and tunnel construction: sinking, widening, and reprofiling with rock splitting cylinders and supplementary removal.
- Natural stone extraction: parallels to gentle block detachment with splitting technology when shafts run in rock.
- Special operations: confined, sensitive environments with requirements for low vibrations and precise control.
Practice-oriented approach models
Opening in an existing access shaft
- Isolate services, remove media, document firestops.
- Rebar locating, define opening edges, temporary shoring.
- Edge notches or core drilling as predetermined breaking lines; removal with concrete pulverizers.
- Breaking of remaining webs using rock and concrete splitters.
- Free-cutting reinforcement with steel shears; edge finishing and fire protection reinstatement.
Widening a rock access shaft
- Define drilling pattern, set splitting cylinders, release section by section.
- Recover spoil, reprofile edges, remove loose material.
- Install built-ins; adapt steel parts with combination shears.
Quality assurance and documentation
- Before/after survey and photographic documentation of the shaft geometry.
- Inspection of surfaces, edges, and protective elements after the works.
- Evidence of material separation and disposal routes.
- Reconciliation with planning documents and release for subsequent trades.