The demolition edge is the visible and measurable boundary between material already removed and the component or rock that remains. It shapes the workflow of concrete demolition, special demolition, rock excavation, tunnel excavation, and natural stone extraction. Those who understand demolition edges can control fracture paths, reduce risks, and deploy the appropriate technique—such as concrete demolition shear or hydraulic splitter—in a targeted way. In the practice of Darda GmbH, demolition edges stand for controlled progress, occupational safety, and precise separation between load-bearing and to-be-dismantled zones.
Definition: What is meant by demolition edge
A demolition edge refers to the emerging fracture line or demolition front that forms when removing concrete, masonry, natural stone, or reinforced concrete. It marks the transition from intact material to the detached, removed area. Demolition edges can be deliberately prepared and guided (controlled fracture edge), for example through splitting boreholes and subsequent splitting, or they arise dynamically in the process, for example during selective biting with a concrete demolition shear. Edge stability is influenced by material strength, reinforcement content, cross-sectional geometry, existing cracks, support conditions, moisture, and temperature. In rock excavation, the demolition edge often represents a natural joint or bedding boundary that is exploited and extended with suitable methods.
Planning and producing controlled demolition edges
Controlled demolition edges result from planning, marking, and methodical execution. In concrete structures, fracture lines are often predefined by creating a drilling pattern along the intended edge. hydraulic splitter or rock wedge splitter apply hydraulic splitting forces in these boreholes and guide the crack along the planned line. This allows the fracture to be guided with very low vibrations—an advantage in special demolition, in sensitive existing structures, and in tunnel construction.
concrete demolition shear shape demolition edges by targeted biting of edge areas: they reduce cross-sections, release edge concrete, and separate concrete parts at joints and predetermined breaking points. In combination with hydraulic power packs and—depending on the task—hydraulic shear or Multi Cutters, edge zones can be exposed, reinforcement cut, and fracture lines prepared. In rock, controlled edges are generated analogously through splitting boreholes and splitters to utilize joints and avoid uncontrolled overbreak.
Geometry, statics, and load behavior at the demolition edge
Demolition edges immediately change a member’s load behavior. Residual cross-sections lose reserves in bending, shear, and torsion. As a rule of thumb: the slimmer the residual cross-section and the closer the demolition edge lies to supports, corbels, or nodes, the greater the local deformations and crack tendency. In reinforced concrete, the position and layout of reinforcement influence whether cracks run stably along the edge or migrate into the remaining structure. In rock, joint spacing and orientation govern edge stability.
Key influencing factors at a glance
- Material properties: compressive/tensile and splitting tensile strength, modulus of elasticity, matrix.
- Cross-section: residual width, slab thickness, ribs, rib orientation, edge radii.
- Boundary conditions: supports, fixity, restraint, temperature, and moisture.
- Reinforcement/inlays: edge distances, anchorage lengths, lap splices.
- Existing separation joints, cuts, or boreholes as preferred fracture lines.
Safety at the demolition edge: edge risk and protective measures
Demolition edges are potential fall and fracture zones. Fundamental safety principles must be checked in general and case by case. Typical measures include temporary barriers, protective and catch devices, and defined working offsets. Mechanical methods such as splitting and shearing reduce vibrations and unexpected spalling compared to percussive methods.
Proven measures
- Fall protection and access control along the edge.
- Before removal: verify load transfer, consider temporary shoring.
- Visually mark cracks, relieve edges with light pre-scoring.
- Tool choice for the surroundings: hydraulic splitter in sensitive environments, concrete demolition shear for edge-proximate, controlled biting.
- Cutting reinforcement with steel shear or hydraulic shear only when the structural member is secured.
Legal requirements, protective measures, and responsibilities can vary by country, project, and hazard situation and must be aligned with the applicable rules of the art and company instructions.
Methods compared: splitting, shearing, cutting
The choice of method determines the quality of the demolition edge, occupational safety, and environmental impacts.
Splitting with hydraulic splitter
Hydraulic splitters generate targeted tensile stresses in the borehole. Advantages are very low vibrations, low emissions, and well-controllable fracture paths. Ideal in existing structures where vibrations, dust, and noise must be minimized, e.g., in special demolition and tunnel interior works.
Biting with concrete demolition shear
Concrete demolition shear crush and shape edges without drilling through. They are suitable for edge-near deconstruction, opening slab edges, creating construction joints, and reducing residual cross-sections. With suitable hydraulic power packs, work remains continuous and controlled.
Cutting and separating
Reinforcement or inserts at the demolition edge can be cut with steel shear and hydraulic shear. In metal structures, vessels, and tanks, tank cutters help produce safe cut edges that then serve as a demolition front. Multi Cutters cover mixed materials when both mineral and metallic components are present at the edge.
Demolition edge in application areas
Concrete demolition and special demolition
During slab openings, edge reductions, or wall breakthroughs, demolition edges arise that guide the subsequent deconstruction. concrete demolition shear shape the edge, hydraulic splitter guide the fracture along predrilled lines. Reinforcement cuts are carried out with steel shear or hydraulic shear, powered by hydraulic power packs. These processes are typical in concrete demolition and deconstruction.
Strip-out and cutting
In strip-out, installations and lines are removed first. At newly created opening edges, clean geometry is important to prepare subsequent steps such as separation cuts or inserting transfer beams. Multi Cutters and hydraulic shear help with mixed materials, before the edge is finished with concrete demolition shear.
Rock excavation and tunnel construction
In rock, bedding planes and joints determine the course of the demolition edge. With splitting boreholes and splitters, the fracture can be guided preferentially along these structures. In tunnels, a low-vibration approach protects the surroundings; controlled edges are important for shotcrete application and linings.
Natural stone extraction
When extracting blocks, edges must be straight and dimensionally accurate. Splitting technology delivers defined fracture surfaces with a small affected edge zone. Subsequent finishing at the edge is performed gently to maximize usable block formats.
Special applications
In areas with explosives, critical media, or sensitive equipment, low vibrations and low sparking are essential. Splitting methods and controlled biting with concrete demolition shear reduce uncontrolled edge break-offs and protect adjacent components.
Influence of demolition edges on noise, vibration, and dust
The way the demolition edge is created directly affects emissions. Splitting methods generate predominantly static crack propagation—noise and vibration levels remain low. Shear work avoids percussive blows and reduces secondary breakage. Clean edges reduce dust because fewer uncontrolled spalls occur and crushing can be done in a defined gradation.
Preparation, marking, and monitoring of the demolition front
Before starting, the planned edge paths are marked. Depending on the method, core drilling or slot cuts are used as guides. During removal, the team monitors crack formation, deformations, and edge stability visually and, if required, with simple measuring aids. A sequential approach—downsizing in stages, load-free sections, timely cutting of reinforcement—increases process safety.
Practical steps
- Define load path concept and edge alignment, consider load redistributions.
- Create drilling pattern or separation cuts along the intended break line.
- Apply splitting forces in a controlled manner; then shape the edge with a concrete demolition shear.
- Cut reinforcement in a defined way; cut metal with steel shear or hydraulic shear.
- Intermediate documentation, visual inspection, adjustment of removal sequence.
Typical mistakes and how to avoid them
- Edge distances of boreholes too small: risk of overbreak—adapt drilling pattern to material and reinforcement.
- Unconsidered supports or restraints: unexpected crack paths—check boundary conditions in advance.
- Reinforcement not fully cut: tie-bar effect—make defined cuts early.
- Removal stages too large: edge instability—choose smaller steps.
- Unsuitable tool choice: increased emissions—prefer splitting or shearing in sensitive environments.
Key metrics and assessment of the demolition edge
Measurable and describable metrics support planning and control. These include edge deviation from the design line, roughness of the fracture surface, residual cross-sectional thickness, distance to reinforcement, and the proportion of overbreak and breakout zones. In rock, joint spacing, bedding orientations, and splitting tensile strength are used. Evaluating these metrics supports the selection between hydraulic splitter, concrete demolition shear, and complementary cutting or shearing tools.
Documentation and quality assurance
Systematic documentation of the demolition edge—photos, sketches, measurements, tools used, and parameters of the hydraulic power packs—facilitates control of the deconstruction. Deviations from the intended edge are detected early and can be compensated by adjusting the drilling pattern, splitting sequence, or shear approach. This procedure is particularly helpful in special demolition, tunnels, and special applications to ensure component protection and process safety.