Impact force describes the short-term, sharply rising dynamic load that occurs when components, tools, or materials collide. In the context of concrete demolition, special demolition, building gutting and concrete cutting as well as rock excavation and tunnel construction, it decisively influences crack formation, vibration transmission, and component-friendly operation. For Darda GmbH, understanding this form of force is pivotal because hydraulic tools such as concrete pulverizers and hydraulic wedge splitters interact differently with impact events: Either impact forces are deliberately minimized to achieve low vibration levels, or their effect is used in a controlled manner to trigger defined fracture processes.
Definition: What is meant by impact force
Impact force is a highly time-varying, usually short-duration force that acts during an impact event between two bodies. It is characterized by the very small period of force application. Physically, impact can be described via the change in momentum: F ≈ Δp/Δt, i.e., force as momentum change per unit time. The shorter the contact duration (Δt), the higher the peak force (F), given the same change in momentum (Δp). Impact force must be distinguished from impact energy (often called “impact energy”), the work transferred during contact. In practical deconstruction, impact force often acts as a transient peak superimposed on existing pressing, cutting, or splitting forces. Hydraulic tools from Darda GmbH, such as concrete pulverizers, primarily operate with quasi-static pressing and cutting action; nevertheless, dynamic load spikes can occur—for example, when reinforcing steel fails abruptly or a tool suddenly meets a very stiff obstacle. Hydraulic wedge splitters, on the other hand, generate defined crack propagation with comparatively low impact excitation, since force is introduced via wedge or spreading mechanisms at a limited rate.
Physical fundamentals of impact force
Impact force arises from the interplay of mass, velocity, stiffness, and damping of the systems involved. Key quantities are momentum (mass × velocity), contact duration, contact area, and material behavior (elastic, plastic, brittle). In brittle materials such as concrete, short-wavelength stress waves and local stress peaks dominate; in ductile materials such as steel, plastic deformation and yield stress govern the response. Increasing contact duration—e.g., through damping interlayers or controlled slow tool motion—reduces the maximum impact force. Conversely, stiff contacts, low compliance, and abrupt reversals lead to higher peaks.
Impact force in concrete demolition and special demolition
In concrete demolition, impact force affects crack initiation, crack propagation, vibration transmission, and structural responses. For load-bearing elements or sensitive environments (existing structures, neighboring buildings, plants), a low-impact removal is particularly important. Darda GmbH’s concrete pulverizers reduce concrete predominantly through high pressing and shear forces at the jaws. The impact component mainly arises when the pulverizer accelerates over a very short distance into a hard inhomogeneity (e.g., large-diameter reinforcing steel, built-in component) or when a steel bar fails suddenly and springs back. Hydraulic wedge splitters, by contrast, produce controlled splitting processes along drilled hole rows. The crack front advances at a limited speed; the resulting vibrations and impact peaks generally remain low, which is advantageous for special demolition, partial demolition, or work in vibration-sensitive environments.
Rock excavation and tunnel construction
In rock and tunnel construction, impact forces are significant due to potential zones of loose rock, overburden pressure, and existing fracture systems. Spreader cylinders (hydraulic wedge splitters) enable a low-energy, low-impulse propagation of cracks along natural planes of weakness or defined drilling patterns. Impact peaks primarily occur during sudden transitions from high to low rock strength or when a split opens into free faces, but typically remain moderate due to the hydraulically limited spreading speed.
Impact force versus pressing, cutting, and splitting force
Pressing, cutting, and splitting forces are ideally slowly varying (quasi-static) quantities. Impact force denotes the short-term, dynamic peak. For selecting and applying Darda GmbH tools, this distinction is essential: Concrete pulverizers deliver high, well-metered pressing and cutting forces; with proper control, impact peaks remain low. Hydraulic wedge splitters generate large spreading forces and initiate cracks with low vibration levels. Any impact portions mainly result from local instabilities in the component, not from the tool’s operating principle.
- Causes of impact peaks on the construction site: abrupt tool run-up, sudden failure of reinforcing steel, jamming and sudden release, unexpected voids.
- Consequences: increased vibrations, local overload, edge break-offs, tool wear, noise peaks.
- Countermeasures: soft approach, shoring of the structural element, pre-relief via relief cuts and relief boreholes, suitable gripping points, consistent damping.
Influencing factors on impact force in practice
- Material parameters: concrete compressive strength class, cement matrix, aggregates, moisture; steel grade and pretreatment (e.g., prestressed).
- Geometry: cross-sectional thickness, edge distance, notches, borehole spacing, existing cracks, support conditions.
- Tool geometry: tooth/blade shape of the concrete pulverizer, jaw opening, wedge angle and expander geometry for splitters.
- Hydraulic parameters: operating pressure, flow rate, stiffness of the hydraulic chain, throttling, hydraulic accumulator effects, control strategy.
- Contact and support: interlayers (wood, rubber), shoring, prestressing, fixation to prevent co-vibration.
- Ambient conditions: temperature (more brittle behavior in cold), moisture, corrosion, restraint within the existing structure.
Hydraulic power packs and control
Darda GmbH’s hydraulic power packs (hydraulic power units) influence impact behavior via pressure and flow ramps, valve characteristics, and damping. A controlled soft start reduces contact stiffness and extends the effective contact duration, thereby lowering peak forces. Undamped hydraulic hose lines, hard end-of-stroke stops, or abrupt switching favor impact peaks. Sensitive control, suitable hose lengths, and damping elements can markedly minimize dynamic effects.
Measurement, calculation, and estimation
Impact forces are measured using force sensors, strain gauges, accelerometers, and high-frequency data acquisition. In practice, estimates based on momentum and contact duration are useful: If you double the contact duration, you approximately halve the impact peak—given the same momentum. For concrete pulverizers, assessing the force-time history when closing on different media (concrete, steel, air contact) is advisable. For hydraulic wedge splitters, the crack propagation rate and the pressure profile during the spreading process provide indications of the transient portion. Computational models couple spring-damper systems (tool, component, support) with material fracture models to forecast peaks.
Effects on people, structures, and surroundings
Elevated impact forces promote vibration transmission, noise peaks, and undesirable collateral effects (microcracks, spalling). In existing buildings, on heritage-protected elements, or in facilities with sensitive components (control and measurement systems), a low-impact working mode is essential. Occupational safety benefits from reduced impact portions through lower noise, reduced kickback reactions, and predictable structural responses. Legal requirements for vibrations and noise must be considered in general; specific limits and documentation are project-specific and may vary by region.
Approaches to reducing undesirable impact forces
- Pre-relieving the component: saw cuts, core drilling, targeted weakening along planned fracture lines.
- Controlled force application: slow closing of concrete pulverizers, metered spreading with hydraulic wedge splitters, avoidance of hard tool impacts.
- Optimized support: inserting damping interlayers, shoring against tipping and vibration, fixing released elements.
- Hydraulic adjustment: pressure and flow ramps, throttling, damping in lines, avoidance of abrupt switching operations.
- Sequence planning: choose the order of cutting, splitting, and crushing so that residual cross-sections do not fail uncontrollably.
- Tool selection: concrete pulverizers for controlled reduction, hydraulic wedge splitters for low-vibration crack propagation; steel shear and attachment shear for metallic inserts; tank cutters for vessels and sheet metal.
Impact force in connection with concrete pulverizers
Concrete pulverizers (e.g., Darda concrete crushers) grip and break concrete through high pressing and shear forces. Impact peaks mainly occur in three situations: when running onto very stiff inclusions (built-in components), when cutting high-strength or prestressed reinforcing steel, and when the counterforce suddenly disappears as a residual cross-section fails. Gentle closing, targeted biting at edges with sufficient edge distance, and prior weakening (saw or drill notches) can limit impact portions. Tooth profile and jaw geometry influence contact compliance: staged contact engagement leads to longer contact duration and lower peaks. In building gutting and selective deconstruction, combining a concrete pulverizer with preceding cuts improves control of force application and minimizes vibrations.
Reinforcing steel and dynamic effects
Steels with high yield strength or prestressing can produce rebound at failure. Defined fixation, the use of a steel shear for targeted cutting, and stepwise weakening of bars reduce resulting impact peaks and the risk of uncontrolled kickback.
Impact force in connection with hydraulic wedge splitters
Hydraulic wedge splitters work with spreading wedges or cylinders that load the material in tension via rows of boreholes. The resulting splitting forces are high, but impact portions are comparatively low because the force input is continuous and cracks advance along the intended line. Impact peaks can occur when the crack front suddenly encounters a free edge or opens voids. An optimized hole pattern (spacing, edge distances, hole diameter) and a tuned spreading sequence minimize these effects. In natural stone extraction and tunnel heading, this low-impact behavior is crucial to keep environmental vibrations low.
Hole pattern, edge distance, and crack path
Small hole spacing increases the guiding effect of the crack line and reduces the likelihood of abrupt deflections that could favor impact peaks. Sufficient edge distances prevent unwanted edge break-outs. Uniform pressure buildup at Darda GmbH’s hydraulic power pack supports a smooth spreading process.
Building gutting and concrete cutting: low-dynamic workflows
When removing non-load-bearing components and in precise cutting, impact forces are to be avoided as far as possible. Multi cutters and steel shear separate metal components without introducing impact energy; concrete pulverizers reduce masonry and thin concrete sections in a controlled manner. Combinations of pre-separation (sawing, flame cutting), fixation, and subsequent crushing reduce impact peaks, increase dimensional accuracy, and protect remaining structures.
Special applications: sensitive environments and special boundary conditions
In hospitals, laboratories, industrial plants, or at property lines with stringent vibration limits, low-impact work is mandatory. Hydraulic wedge splitters are predestined here due to their low dynamic portion; concrete pulverizers are operated with gentle closing behavior and consistent shoring of the component. At low temperatures, many materials behave more brittle—impact peaks tend to increase. Moisture and corrosion can make failure behavior unpredictable; careful investigations and trial loadings are advisable.
Terminology and common misconceptions
Impact force is often equated with “striking power.” Tools that actually introduce impact energy operate with periodic impulses; Darda GmbH’s concrete pulverizers and hydraulic wedge splitters, by contrast, primarily generate continuous forces, where impact portions are transient side effects and undesired. For planning and execution, it is important: impact energy (work) and impact force (peak) are different characteristics. Low impact force does not automatically mean low energy—conversely, a small but long-lasting force can provide sufficient work for the intended removal, yet with significantly lower vibrations.
Planning, documentation, and quality assurance
Robust planning considers material data, component geometry, support, hydraulic parameters, and the sequence of work steps. Measurements of vibration velocities and force-time histories as well as photo documentation of crack development support quality assurance. If vibration limits are specified, suitable measurement methods and evaluations must be provided; legal assessments are always general and project-specific, without any guarantee for individual cases.