Blast pressure denotes the pressure-induced effect of an explosion or controlled blasting on air, solids, and liquids. In the practice of concrete demolition, special demolition, rock excavation, tunnel construction, and natural stone extraction, mastering blast pressure determines whether structures and rock are separated in a targeted manner or whether unwanted side effects such as overbreak, vibrations, and noise occur. In many application scenarios, blast pressure is compared or combined with alternative hydraulic methods—such as hydraulic rock and concrete splitters or concrete pulverizers from Darda GmbH—to achieve precise, low-emission, and low-vibration results.
Definition: What is meant by blast pressure
Blast pressure refers to the highly dynamic pressure rise over time that results from the detonation of an explosive. The detonation generates a shock wave and expanding reaction gases. This combination leads to abrupt loads on the surrounding medium. One typically distinguishes:
- Detonation/shock-wave pressure: a very steep, short-lived pressure impulse at the front of the shock wave.
- Gas expansion pressure: a subsequent, longer-lasting pressure component due to expanding gases, particularly effective in coupled boreholes.
- Air overpressure: propagation of the shock wave in air; relevant for sound, glass breakage, and safety.
The magnitude of blast pressure depends, among other factors, on the type of explosive, charge geometry, coupling to the borehole, stemming, the properties of the rock or concrete, and the distance. In day-to-day demolition and extraction work, the abstract peak pressure is less decisive than the resulting effect: crack formation, detachment, fragmentation, and the transmission of vibrations.
Physical fundamentals and measurement quantities
The effect of blast pressure is based on shock waves and trailing gases. In solids, radial and tangential stresses arise; if the tensile strength is exceeded, cracks form and material is removed. In air, the load is described as an overpressure-time history. Important measurement and planning quantities are:
- Coupling and borehole conditions (diameter, fill ratio, water-filled): influence pressure transfer into concrete or rock.
- Stemming: increases the duration and effectiveness of gas pressure.
- Scaled distance: links charge mass and measurement distance, serving to predict overpressure and vibrations.
- Material parameters: compressive and tensile strength, modulus of elasticity, jointing, reinforcement in concrete.
- Measurement methodology: high-pressure sensors in the borehole, blast meters for air overpressure, geophones for vibrations.
In contrast to abrupt blast pressure, hydraulic tools from Darda GmbH—such as hydraulic wedge splitters or concrete pulverizers—generate controlled, more slowly rising forces. They deliberately exceed local tensile strength, minimize shock waves, and thus reduce emissions such as vibration, air overpressure, and fly ash.
Effects of blast pressure on concrete and rock
Blast pressure leads to high compression near the borehole, followed by crack formation and fragmentation. In heterogeneous construction materials such as reinforced concrete, the pressure wave interacts with reinforcement; in jointed rock, discontinuities steer crack propagation. In urban deconstruction, the goal is to create the intended separation plane without damaging adjacent components or infrastructure.
Crack formation, overbreak, and edge quality
High pressure peaks can cause uncontrolled overbreak. Pre-splitting, reduced charge quantities, or linear weakening cuts improve edge quality. Alternatively, rock wedge splitters and concrete pulverizers generate defined fractures along planned lines—an advantage when separating foundations, slabs, or edge beams.
Blast pressure in application areas
The handling of blast pressure varies depending on project goal, environment, and material. The following examples show typical requirements in Darda GmbH’s application areas.
Concrete demolition and special demolition
In densely built-up areas, air overpressure, vibrations, and secondary effects (dust, noise) are particularly sensitive. Consequently, controllable methods are frequently used: concrete pulverizers reduce components in a controlled manner, while hydraulic wedge splitters open up massive elements along drilling patterns. When blast pressure is used, minimal charge quantities, stemming, and monitoring are paramount.
Strip-out and cutting
Selective deconstruction in existing structures calls for local interventions. Combination shears, Multi Cutters, steel shears, and concrete pulverizers separate reinforcement, sections, sheets, and composite cross-sections without explosives. Blast pressure plays little role here, because the separation effect is produced mechanically and hydraulically. In sensitive areas—for example, with tanks—safe working against ignitable atmospheres must also be considered; tank cutters enable cold, controlled cuts under appropriate protective measures.
Rock excavation and tunnel construction
In rock, blasting-based methods dominate. The aim is the direction of blast pressure in the direction of excavation: suitable drilling pattern, charge distribution, coupling, and stemming. To reduce overbreak at protective screens, abutments, or shotcrete linings, low charge densities are used. In zones with restrictions on vibrations or air overpressure, rock wedge splitters and hydraulic wedge splitters are an option to loosen blocks or define contours before further processing with concrete pulverizers.
Natural stone extraction
For high-quality blocks, edge quality takes precedence over yield. High blast pressure causes unwanted microcracks. Therefore, weak charges, pre-drilled lines, or hydraulic splitting are preferred. Controlled splitting produces smooth separation surfaces that simplify further processing.
Special applications
In projects near sensitive infrastructure, listed components, or operating facilities, the low emission level is decisive. Where blast pressure can only be used to a limited extent, combined sequences of drilling, hydraulic splitting, and mechanical crushing are employed—supported by powerful hydraulic power units to supply the tools.
Safety, permits, and environmental aspects
The use of blast pressure is subject to strict requirements. Qualifications, permits, and a project-specific safety concept are essential. In general, the following must be considered:
- Risk assessment including distances, shielding, and protection against fragments and air overpressure.
- Vibration and noise monitoring to comply with limits and guideline values, coordinated with residents and operators.
- Dust and emissions mitigation through watering, enclosure, or alternative methods.
- Documentation of drilling patterns, charging parameters, and measurements.
Hydraulic methods avoid typical risks of blast pressure such as sudden overpressures or projectiles. However, they also require professional planning, for example regarding retention concepts, load transfer, and the stability of the remaining structure.
Measurement, prediction, and documentation
For planning and verification, scaling relationships between charge quantity, distance, and effect are used. In practice, it is useful to employ reference values and test fields to derive project-specific correlations. Robust documentation includes:
- Drilling and charging logs with coupling, stemming, and sequencing.
- Measurement concepts for air overpressure, vibration, and, if applicable, component loading.
- Assessment of edge quality and fragmentation in the target area.
- Adjustment of parameters based on measurement and visual findings.
Practical alternatives to blast pressure-based methods
Where blast pressure is technically, organizationally, or legally limited, controlled methods are available:
- Hydraulic wedge splitters: hydraulic expansion in the borehole generates tensile cracks without a shock wave; suitable for massive foundations, rock, and thick walls.
- Concrete pulverizers: powerful, pinpoint crushing of reinforced concrete, often in combination with Multi Cutters or steel shears to separate reinforcement.
- Rock wedge splitters: targeted release of blocks in extraction and tunnel heading, with good edge control.
- Combination shears and tank cutters: versatile cutting and separation tasks when explosives are unsuitable or prohibited.
The tools are powered by hydraulic power packs and enable sequential workflows: preparation by drilling, splitting along defined lines, secondary breakage and sorting—with a low emissions profile and high repeatability.
Selection criteria: blast pressure or hydraulic splitting/crushing?
The choice of method depends on the objective, environment, and boundary conditions. Helpful criteria are:
- Environmental sensitivity: proximity to people, buildings, facilities; limitation of vibration, noise, air overpressure.
- Material and geometry: thickness, reinforcement ratio, joints, required edge quality.
- Performance target: block sizes, daily output, cycle constraints.
- Permits: feasibility, conditions, time windows.
- Process chain: availability of drilling technology, hydraulic power packs, and attachments.
In practice, a combination often proves effective: blast pressure where removal performance and breakage are required; hydraulic splitting and concrete pulverizers where precision, edge quality, and emissions control prevail.
Planning and execution: best practices
A structured approach reduces risks and improves result quality:
- Define objectives and set quality criteria (edge, fragment size, vibration limits).
- Compare variants of blast pressure-based and hydraulic methods, including construction logistics.
- Test field to calibrate charging parameters or splitting configurations.
- Monitoring and ongoing parameter tuning during operation.
- Documentation and evaluation for transferability to subsequent work sections.
Terminology and technical classification
Blast pressure encompasses the entire pressure-side portion of blasting effects—from the shock wave to gas expansion pressure—and interacts with material properties and boundary conditions. Distinct from this are vibrations as a kinematic consequence, as well as hydraulic splitting forces of mechanical tools. In Darda GmbH projects, blast pressure is technically classified and—where necessary—replaced or supplemented by controlled splitting and crushing methods.