The term breakout wedge describes both the wedge-shaped body of material that is detached from concrete or rock during controlled demolition or extraction work and the technical operating principle used to deliberately initiate such a breakout. In concrete demolition, strip-out, as well as in rock excavation and tunnel construction, the wedge effect is used to build up stresses and steer cracks. In practice, this is often implemented without explosives by means of hydraulic rock and concrete splitters and complemented by concrete pulverizers to remove the released wedge and perform secondary breaking.
Definition: What is a breakout wedge
A breakout wedge is a wedge-shaped section of concrete or natural stone that is separated from the composite along existing or artificially created planes of weakness (borehole series, joints, cracks, edges) by wedge action. Technically, this is achieved via a wedge set (center wedge with counter-wedges) or via a pincer-like force transmission. The term is also used in rock mechanics for wedge failure, in which a block bounded by joint systems detaches. In all cases, controlled crack initiation and guidance are central in order to carry out the breakout in a predictable, low-vibration manner and with defined geometries.
Operating principle and mechanics of the breakout wedge
The wedge effect is based on converting an applied compressive force into radial stresses that split the concrete or rock along the weakest line. With hydraulic wedge sets, a center wedge is driven between two counter-wedges. As a result, normal and shear stresses increase in the borehole zone until a crack forms and the wedge-shaped breakout propagates along the prescribed planes of weakness. In reinforced concrete, the position and diameter of the reinforcement influence wedge formation; here the splitting process is often combined with concrete pulverizers or combination shears to cut reinforcing bars in a controlled way and remove the wedge.
Breakout wedge in concrete demolition and specialized deconstruction
When dismantling foundations, slabs, walls, or massive components, the breakout wedge is used to divide members into manageable segments. The aim is a low-vibration, well-planned removal with reduced noise emission and minimal impact on adjacent structures.
Typical procedure
- Preparation and marking of the wedge geometry (cut edges, crack-propagation path).
- Drilling the preholes to suit the wedge set (borehole diameter, depth, center spacing).
- Use of rock and concrete splitters to initiate the crack and release the breakout wedge.
- Secondary breaking and removal of the wedge with concrete pulverizers; if reinforcement is present, additionally cut the bars.
- Edge protection, transport away, and, if necessary, further cutting with Multi Cutters or combination shears.
Specifics for reinforced concrete
- Reinforcement can deflect the crack; adjust wedge size accordingly.
- Before lifting the wedge, deliberately expose the reinforcement and cut it with combination shears or steel shears.
- Size the hydraulic power packs so that the necessary pressure force for the splitting process is reliably available.
This approach is established in concrete demolition and specialized deconstruction as well as in strip-out, for example when creating wall openings or removing slab fields in commercial buildings.
Breakout wedge in rock excavation and tunnel construction
In rock, breakout wedges are planned along joint systems and released using wedge action. In hard rock, borehole rows and hydraulic wedge sets enable extraction without explosives. In alternating strata, the position, inclination, and angle of friction of the discontinuities are taken into account to avoid uncontrolled secondary breakage.
Planning and execution
- Orient the wedge along natural joints or along a pre-drilling pattern.
- Cascaded deployment of wedge sets to release large volumes step by step.
- Shore and secure the remaining berms; remove released wedges in a controlled manner with shears.
For massive blocks, in addition to rock and concrete splitters, rock splitting cylinders are also used to further widen the wedge faces and facilitate handling. This is particularly relevant in rock excavation and tunnel construction as well as in natural stone extraction.
Drilling pattern, wedge geometry, and sizing
The quality of a breakout wedge stands and falls with the drilling pattern and geometry. Depth, diameter, and spacing of the boreholes define the subsequent crack path. Edges, openings, and member transitions often serve as natural crack starters.
Guidelines for practice
- Borehole diameter: match to wedge set and material; too small increases friction, too large reduces force transmission.
- Borehole depth: at least 80–90% of the planned wedge height to avoid blind cracks.
- Center spacing: choose so that cracks overlap and form a continuous wedge.
- Edge distances: sufficiently large to prevent spalling at exposed edges.
Sizing is based on material strength, member thickness, and the available hydraulic pressure of the hydraulic power packs. Where reinforcement is present, the drilling pattern is chosen so that bars are exposed and then cut with concrete pulverizers or steel shears.
Applications and combinations with tools
The breakout wedge is a central working principle in several application areas:
- Concrete demolition and specialized deconstruction: segmentation of massive members, foundation removal, slab penetrations.
- Strip-out and cutting: openings, penetrations, partial wall or slab openings.
- Rock excavation and tunnel construction: block release, crown and sidewall secondary breakage, contour control.
- Natural stone extraction: releasing raw blocks along natural joints or defined drilling patterns.
- Special applications: work in sensitive areas with strict limits on vibration and noise.
Depending on the task, rock and concrete splitters are used for crack initiation and combined with concrete pulverizers for gentle secondary breaking. For metal inserts, combination shears, Multi Cutters, and steel shears are suitable; for special applications, a tank cutter can be used additionally.
Safety aspects and organizational measures
Work with breakout wedges requires forward-looking hazard analysis. Wedge movements release stored energy, which is why stable support, retention systems, and a restricted zone are necessary. Personal protective equipment, low-dust drilling technology, and a coordinated signaling chain are essential. Legal requirements may vary depending on location and activity; compliance with the relevant rules of the art and official conditions is fundamentally required.
Typical risks
- Uncontrolled crack deflection due to reinforcement or inhomogeneities.
- Spalling at edges when edge distances are too small.
- Overloading of wedge sets due to unsuitable borehole diameter or insufficient lubrication.
Sources of error and practical tips
Many problems can be avoided by a systematic approach. Clean drilling and correct placement of the wedge set are crucial.
- Blow out and clean boreholes to reduce friction.
- Align the wedge set straight; skewing leads to loss of force and material damage.
- Check hydraulic pressure and increase gradually; monitor crack propagation acoustically and visually.
- Secure the wedge movement and immediately support or remove the released block.
- For reinforced concrete: use concrete pulverizers early at the crack opening to cut the reinforcement in a targeted manner.
Maintenance of wedge sets and hydraulics
Component service life depends on proper care. Inspect wedge faces regularly and lubricate sparingly, check cylinder seals, and inspect hose lines for chafing. Change hydraulic oil and filters according to the manufacturer’s instructions for the hydraulic power packs. Clean storage protects against corrosion and increases process reliability.
Quality assurance and documentation
For reproducible results, drilling patterns, hydraulic parameters, and wedge geometries should be documented. Dimensional checks on the removed wedge (angle, height, fracture surface) facilitate optimization of the next work steps. For sensitive structures, measuring vibrations and noise levels is useful to demonstrate compliance with requirements.