Natural stone is one of the oldest and at the same time most versatile construction materials. Its origin in geological processes shapes properties such as strength, porosity, and cleavability—and thus the way it is extracted, processed, installed, and deconstructed. In practice, natural stone topics touch many fields of application: from natural stone extraction in the stone quarry through rock excavation and tunnel construction to building gutting and cutting of masonry. Methods such as controlled splitting or gripping and crushing—for example with hydraulic rock and concrete splitters or concrete demolition shears from Darda GmbH—play an important role when precise handling of rock with low vibration levels and in a material-appropriate manner is required.
Definition: What is meant by natural stone
Natural stone refers to naturally formed, solid rocks without artificial binders. They are obtained as raw blocks or bulk material, mechanically processed (e.g., sawn, split, bush‑hammered), and used in structures, landscape architecture, civil engineering, and interior fit-out. Natural stone includes magmatic (e.g., granite, basalt), sedimentary (e.g., limestone, sandstone), and metamorphic rocks (e.g., gneiss, marble, quartzite). The material‑typical combination of high compressive strength and comparatively low tensile and flexural tensile strength leads to brittle fracture behavior. These properties determine how the material can be drilled, cut, split, and broken—and explain why tools for controlled splitting and targeted gripping are so widespread in extraction and deconstruction.
Formation and the rock cycle
Natural stone forms within the geological cycle: solidification of magmatic melts, deposition and lithification of sediments, and transformation of existing rocks under pressure and temperature. These processes produce textures (grain bonding, bedding, joints) and mineral combinations that decisively influence mechanical parameters and workability. For practice, natural zones of weakness—bedding planes, joint systems, stratification—are significant and can be specifically exploited during splitting to detach blocks with low energy input. In compact, joint‑poor rock, generating cracks requires peak pressures produced by hydraulic wedge and split systems.
Geological classification and properties
Assigning rocks to magmatic, sedimentary, and metamorphic groups helps estimate behavior and suitable procedures. It is important not only to know the rock by name, but also to assess its bonding, grain structure, porosity, and joint distribution.
Magmatic rocks
Granite, diorite, and gabbro are coarse‑grained, strong in compression, and often poor in joints; basalt is fine‑grained to dense. They are abrasive when drilling and sawing, but respond well to wedge forces if borehole geometry and edge distance are suitable. In massive granites, stone and concrete splitters with borehole wedges are a proven way to detach blocks without blasting.
Sedimentary rocks
Limestone and sandstone frequently show bedding and stratification planes. Their porosity varies widely, as do frost and salt resistance. Pronounced bedding planes facilitate wedging and establishing crack lines. In mortared natural stone masonry, concrete demolition shears grip reliably because they engage rock pieces together with mortar joints and produce shear fractures.
Metamorphic rocks
Gneiss, quartzite, slate, and marble are transformed by pressure and temperature. They possess oriented fabrics (foliation, schistosity) that define preferred splitting directions. With proper alignment of wedge forces, precise fracture edges can be produced; with unfavorable alignment, spalling may occur. A well‑thought‑out drilling pattern is particularly important here.
Mechanical key values for planning and procedures
The selection of procedures and tools is guided by reliable parameters. For practice, the following are especially relevant:
- Compressive strength: roughly 50–300 MPa (strongly rock‑dependent)
- Splitting tensile strength: typically 2–15 MPa (brittle behavior)
- Bulk density and porosity: influence on water uptake, frost and salt resistance
- Modulus of elasticity: stiffness, vibration transmission, crack propagation
- Abrasivity: tool wear when drilling/sawing
- Joint and bedding systems: crack guidance, borehole spacing, block sizes
In application this means: the higher the compressive strength and the lower the splitting tensile strength, the more efficiently a hydraulic wedge acts. In heterogeneous, jointed rocks, crack steering via drilling pattern and wedge arrangement is decisive.
Extraction in the stone quarry: splitting instead of blasting
In sensitive locations, with monument protection, or near buildings, low‑vibration methods are preferred. Here, stone and concrete splitters with splitting cylinders enable block detachment along targeted rows of boreholes. This reduces immissions (vibrations, noise, dust) and allows good block yield.
Drilling pattern and wedge technique
Borehole diameter, center spacing, and penetration depth determine the crack line. Common are parallel rows with edge distances that minimize spalling. Hydraulically expanding wedges generate linear tensile stresses; the crack propagates preferentially along existing weakness planes.
Crack steering and block size
Before splitting, the joint pattern is read. The goal is to detach large, rectangular raw blocks. Where natural boundaries are lacking, drilling patterns define the later block geometry. A coordinated interplay of borehole diameter, wedge force, and sequence of steps is decisive.
Occupational safety and surroundings
Protection against rockfall, controlled exclusion zones, and dust suppression are mandatory. The hydraulic approach reduces the risk of uncontrolled breaks; nonetheless, flying fragments and secondary break must be considered.
Rock excavation and tunnel construction
In rock masses, the focus is often on profile enlargements, niche formation, or removing obstacles. Hydraulic splitting is precise and material‑appropriate, especially in confined, vibration‑sensitive situations within rock demolition and tunnel construction. Hydraulic power units supply the splitting cylinders; the energy is purposefully converted into crack formation.
Confined spaces, high precision
Where blasting bans apply or vibrations are critical, splitting cylinders can produce cut‑outs without damaging surrounding structures. In combined structures of natural stone and concrete, concrete demolition shears allow targeted detachment of partial areas, while adjacent rock is worked with splitting technology.
Demolition of natural stone masonry and mixed structures
Historic masonry combines natural stone with mortar, sometimes supplemented by concrete infills or steel anchor points. Concrete demolition shears grip components with positive engagement, generate compressive and shear forces, and also detach irregular stone layers. For additions and conversions, the combination of shears (for mortared areas) and splitters (for massive stones or rock interfaces) is a material‑appropriate way to keep vibrations low.
Selective deconstruction
Where reuse of natural stone is intended, gentle splitting with minimal fracture zone formation supports reprocessing as backfill, paving, or dimension stone.
Cutting and sawing of natural stone
In addition to splitting, drilling and sawing are used. The choice between dry and wet cutting affects tool life, cut quality, and dust generation. In situations with steel or concrete portions—for example, in natural stone facades with backing concrete elements—combination shears or multi cutters can additionally be used to expose and separate non‑mineral components.
Dust and noise control
Water‑cooled sawing reduces fine dust and improves the cut edge. With hydraulic splitting operations, noise emissions are lower but remain relevant due to drilling; a coordinated sequence reduces the burden on the surroundings.
Planning, structural analysis and permits
Interventions in load‑bearing natural stone constructions require careful assessment of structural stability. Measures should be planned on the basis of verified load paths, edge distances, and safeguarding measures. Permits and conditions (e.g., immissions protection) depend on location and project; early coordination with the competent authorities is advisable. The guidance presented here is general and does not replace an individual assessment.
Sustainability and reuse
Natural stone is durable and often reusable. Selective deconstruction—preferably using splitting and shear procedures—preserves larger formats, lowers processing costs, and reduces breakage. Material that is not suitable again as dimension stone is often well suited as frost protection or base course material. Choosing the method appropriate to the material can thus combine ecological and economic benefits.
Practical guide: selecting procedures and tools
The following considerations help in making material‑ and situation‑appropriate decisions:
- Dense, joint‑poor rock: controlled splitting with hydraulic wedge systems; keep the drilling pattern tight and respect edge distances.
- Rock with pronounced bedding/joints: align crack lines with natural weakness planes, reduce drilling depths, meter wedge forces.
- Mortared natural stone masonry: concrete demolition shears for gripping, pressing, and shear fracture; use splitters additionally for massive blocks.
- Mixed constructions with steel/concrete portions: combine shears (mineral) with multi cutters or combination shears (metal) to separate composite interfaces.
- Vibration‑sensitive environment: prefer hydraulic splitting methods, perform saw cuts in a targeted and low‑dust manner, optimize drilling operations.
- Reuse intended: prioritize splitting and gripping methods with low fracture zone depth, plan lifting and storage in advance.
Safety and ergonomics
Hydraulic forces generate high stresses in a short time. Personal protective equipment, defined exclusion zones, and clear hand‑signal communication are essential building blocks. Splitting operations can cause flying fragments; shielding and correct positioning of operators reduce risks. Hydraulic hose lines must be protected against abrasion; leaks must be remedied immediately.
Common mistakes and how to avoid them
- Unsuitable drilling pattern: leads to uncontrolled cracks and spalling. Remedy: adapt geometry to rock and block size.
- Edge distances too small: edge breaking instead of crack progression along the line. Remedy: maintain safety distance, consider load transfer.
- Lack of alignment to bedding/joints: higher forces, more spalling. Remedy: read the rock fabric, plan crack guidance.
- Overloading the shear in masonry: point fractures, material loss. Remedy: meter gripping position and pressure, relieve loads before the cut.
- Insufficient dust and noise mitigation: hazards to people and surroundings. Remedy: wet cutting, extraction, adapted process sequence.
Practical terms: briefly explained
Joint and bedding
Natural separation planes in rock along which cracks propagate more easily. Crack lines should run as parallel as possible to these planes.
Drilling pattern
Geometric arrangement of boreholes for splitting or sawing operations. Parameters are diameter, depth, spacing, and edge distance.
Splitting tensile strength
The rock’s resistance to tensile stresses. The lower the value, the more efficient splitting with wedge systems becomes.