The impact direction describes the direction in which a mechanical or hydraulic force is introduced into a structural element, a rock mass, or a workpiece. In concrete demolition, special demolition, strip-out, and rock demolition, it decisively influences crack formation, separation planes, and the flow of forces. For applications with tools from Darda GmbH—such as concrete demolition shears as well as rock and concrete splitters—the correct alignment of the impact direction is crucial to steer fracture progressions purposefully, separate components in a controlled manner, and protect adjacent structures.
Definition: What is meant by impact direction
Impact direction is understood as the direction of application of force of a tool on a material. It is the direction of the resultant force vector that acts from the tool (e.g., shear, splitting wedge, cutter) through contact surfaces into the component. In practice one differentiates between:
- Pressing or splitting direction in hydraulic wedge and cylinder systems of rock and concrete splitters: the impact direction runs essentially along the wedge axis or the cylinder axis.
- Cutting or closing direction with concrete demolition shears, combination shears, multi cutters, steel shears, and tank cutters: the impact direction follows the closing path of the blades or the jaws.
In static to quasi-static applications—typical for hydraulic splitting and cutting processes—the impact direction affects the location of compression and tension zones, the orientation of principal tensile stresses, and the preferred crack paths. It is therefore a fundamental parameter for precision, safety, and efficiency in concrete and rock demolition.
Importance of the impact direction for crack steering and fracture control
The impact direction governs the direction in which cracks initiate, how the splitting plane and fragment size develop, and which forces dissipate into adjacent areas. If it is perpendicular to the desired separation plane, this favors a clear, planned break with minimal secondary cracking. An unfavorable alignment can, by contrast, lead to spalling, uncontrolled shear fractures, and increased tool wear. In strip-out and special demolition, a properly chosen impact direction helps protect services, reinforcement layers, adjacent components, and surfaces. In rock demolition and tunnel construction, it influences whether existing joints are exploited or undesirably activated. For natural-stone extraction it is central to releasing usable blocks along natural planes of weakness with minimal loss.
Impact direction with concrete demolition shears: jaw geometry, reinforcement, and component edges
With concrete demolition shears, the impact direction is defined by the closing path of the jaws and the geometry of the blades. The aim is to generate tensile stresses where the fracture should open in a controlled manner, and compressive stresses where the material can be supported.
Component geometry and supports
The jaws should be applied so that the impact direction acts away from load-bearing areas and toward the planned separation line. On slabs and decks, positioning near the free edge helps activate the tension zone and deliberately initiate peeling fractures. For walls, support oriented to the impact direction against deflection is important to avoid uncontrolled spalling.
Reinforcement layout
If the impact direction runs transverse to the primary reinforcement, concrete is removed efficiently, but remaining reinforcement may be stressed more. A parallel impact direction reduces shear peaks in the bars, but affects fragment size. Changing the bite points along the reinforcement layout helps produce defined piece sizes.
Edges, openings, and embedded components
Near edges, recesses, or embedded components, select the impact direction so that demolition forces do not enter critical details. An offset approach with a slightly offset impact direction prevents edge breaks and minimizes secondary cracks.
Impact direction with rock and concrete splitters: wedge angle, borehole axes, and splitting plan
Rock and concrete splitters transmit the impact direction via wedges or splitting cylinders into boreholes. The resulting pressing direction is essentially collinear with the borehole axis and normal to the planned splitting plane.
Drilling pattern and splitting direction
Borehole position, depth, and spacing define the direction of the splitting plane. A straight drilling pattern enables a uniform crack advance line, whereas a curved row of boreholes can intentionally deflect the fracture path. Sufficient edge coverage prevents undesired spalling at edges.
Material and structure
In concrete, aggregates, strength class, and component thickness influence the required splitting energy and thus the response to the impact direction. In natural stone, bedding, joints, and foliation must be considered: the impact direction should preferably act perpendicular to the desired separation planes and parallel to existing natural weaknesses to use energy efficiently.
Reinforced components
With reinforced concrete, the impact direction can be chosen so that the concrete is separated first and the reinforcement becomes accessible. The bars are then cut using suitable tools such as concrete demolition shears, steel shears, or combination shears.
Planning the impact direction: procedure from analysis to execution
- Existing-condition survey: component geometry, materials, reinforcement drawings, boundary conditions, adjacent uses.
- Objective definition: desired separation planes, fragment sizes, protection zones.
- Specification of the impact direction: alignment of the tools (shear orientation, wedge axes, shear position) along the planned fracture or splitting plane.
- Drilling and cutting planning: drilling patterns, bite points, sequence of attacks, intermediate supports.
- Hydraulic tuning: select pressure and flow rate of the hydraulic power pack so that the impact direction acts in a controlled manner without being overdriven.
- Trial step: short test attack to check the crack response; adjust the impact direction if required.
- Monitoring: visual inspection of the crack front, readjusting bite points and angles.
Factors influencing the effective impact direction
- Component thickness and support: stiff supports change the stress distribution; the impact direction must match.
- Moisture and temperature: material behavior varies, particularly under frost or strong heating.
- Hidden inserts: services, embedded parts, tendons require a conservative choice of impact direction and a stepwise approach.
- Tool geometry: jaw shape, blade position, wedge angle, and cylinder stroke define the actual direction of force application.
Practice in concrete demolition, rock demolition, and tunnel construction
In concrete demolition, consistent impact-direction planning supports the selective separation of concrete and reinforcement. Concrete demolition shears are guided so that the fracture line develops away from openings and anchors. With massive foundations or blocks, rock and concrete splitters enable controlled opening in sections—the impact direction follows the borehole axes and is implemented step by step. In rock demolition and tunnel construction, the impact direction is often planned parallel to joint orientations to exploit existing weaknesses and avoid overbreak.
Hydraulic power packs: pressure, flow rate, and controlling the impact direction
Hydraulic power packs supply the pressure and flow required to build tool forces. They do not define the direction of the force, but they influence how steadily and sensitively the impact direction can be executed. Clean pressure control and proper hose routing prevent jerky load spikes that could unintentionally deflect the crack front.
Safe implementation: protection zones, rebound effects, and control
Adequate securing of protection zones, compliance with safety distances, and handling rebound effects are fundamental. The impact direction should be chosen so that released pieces fall into controlled areas or separate along planned joints. Notes on occupational safety are always to be understood in general terms and do not replace project-specific risk assessments or regulatory requirements.
Quality assurance and documentation
A simple but effective check is performed by viewing the crack front, marking splitting lines, and adjusting bite points. Photos, sketches of the planned and actual impact directions, and measurements (pressure, stroke, time) from the work steps facilitate assessment of the approach and serve as evidence of controlled, material-appropriate work.
Typical errors and how to avoid them
- Unclear target separation plane: leads to changing impact direction and uncontrolled fracture patterns—therefore create clear splitting and cutting plans in advance.
- Too close to edges: direct introduction of the impact direction into edges causes spalling—better start offset and lead along edges.
- Disregarding the reinforcement: selecting the impact direction without reference to bar layout increases resistance—include the reinforcement drawing and stage the procedure.
- Overdriving due to excessive pressure: jerky load spikes can deflect cracks—operate the hydraulics in a controlled manner and use intermediate steps.
Application in strip-out and special operations
In strip-out operations, the impact direction is often chosen so that components are released layer by layer to reduce vibration and noise. In special operations—for example in sensitive environments—concrete demolition shears and rock and concrete splitters are particularly suitable thanks to their controlled, low-shock force application to guide the impact direction precisely along defined separation lines.