The subsoil determines the feasibility, safety, and efficiency of concrete demolition, special demolition, rock excavation, tunnel construction, strip-out, and natural stone extraction. Its characteristics influence the choice of methods, the sizing of tools, and the sequence of work steps. Whether massive reinforced concrete, layered natural stone, jointed rock, or inhomogeneous masonry—only a well-founded subsoil analysis enables a controlled, low-vibration approach with tools such as concrete demolition shears or rock and concrete splitters from Darda GmbH.
Definition: What is meant by subsoil
Subsoil in the construction engineering and geotechnical context refers to the entirety of load-bearing or to-be-processed materials and layers on or in which work is carried out: concrete, reinforced concrete, masonry, natural stone, rock, asphalt, screed as well as loose rock and backfills. It comprises physical and structural properties (density, strength, porosity, moisture, crack and joint systems, reinforcement) that decisively determine how loads are transferred, how cracks propagate, and which removal or separation methods are appropriate.
Geotechnical parameters and structure of the subsoil
For planning and execution in deconstruction and demolition contexts, the following characteristics of the subsoil are decisive:
- Compressive and tensile strength: determine the required splitting and cutting forces.
- Crack and joint systems: influence crack guidance, block formation, and fracture surfaces.
- Reinforcement ratio and position: affects the suitability of concrete demolition shears compared to splitting methods.
- Stratification, bedding, grain fabric in natural stone and rock: guides the split line and removal behavior.
- Moisture, porosity, carbonation: change the brittle vs. ductile-brittle behavior of concrete and masonry.
- Built-ins and voids: utilities, prestressing cables, fillings or backfills influence safe processing.
Role of the subsoil in concrete demolition and special demolition
In concrete demolition and special demolition, the subsoil determines the ratio of cutting, splitting, and crushing. With heavily reinforced reinforced concrete, concrete demolition shears are appropriate to engage concrete and reinforcement separately, reduce load-bearing cross-sections in a controlled manner, and dismantle components section by section. In massive, brittle concrete with low reinforcement, rock and concrete splitters enable targeted crack initiation and low-vibration fracture. hydraulic power units from Darda GmbH provide the required pressures, while hydraulic wedge splitter in rock or natural stone release large blocks along natural weakness zones.
Subsoil types and typical properties
Concrete and reinforced concrete
Concrete subsoils range from lightly reinforced foundations to high-strength, densely reinforced members. Relevant aspects are strength class, reinforcement cover, concrete age, carbonation depth, moisture, and existing cracks. With dense reinforcement and limited access, concrete demolition shears offer controlled cross-section reduction and separation, whereas in massive, lightly reinforced members rock and concrete splitters introduce splitting forces via core drilling.
Masonry
Masonry is inhomogeneous. Unit geometry, mortar quality, bed joints, and defects influence the fracture pattern. Mechanical splitting can act along bed and head joints; in mixed masonry, pre-cuts and a combination of crushing and splitting have proven effective. Hydraulic shears with adapted jaw geometry reduce detachment and breakout risks on adjacent components.
Rock and natural stone
Rock masses possess joints, bedding planes, and benches. The orientation of these weakness zones guides the split line. Hydraulic wedge splitter make use of this to release precise blocks—in natural stone extraction as well as in tunnel construction. In very tough rocks a tighter borehole sequence is necessary; in bedded material larger spacings suffice provided joint continuity is adequate.
Asphalt, screeds, subfloors
These layers are thinner and tougher. Pre-cutting, sectional lifting, and crushing limit damage to the load-bearing subsoil. Moist subsoils or bound base layers require an adjusted sequence to avoid vibrations and delaminations.
Loose rock and backfills
Inhomogeneous backfills, fills, and soils are critical as bearing surfaces. They influence machine support and load paths during removal. Compaction, support, and, if necessary, temporary foundations must be planned.
Investigation and assessment of the subsoil
A systematic subsoil survey reduces risks and increases process reliability. Sensible steps are:
- Visual inspection: cracks, spalling, efflorescence, moisture marks, settlements, edge integrity.
- Probing and cores: sampling for strength estimation, porosity, and reinforcement layout.
- Locating and testing methods: rebar detection, rebound measurements, impact-echo/ultrasound for member homogeneity.
- Component and load analysis: load-bearing action, supports, restraints, bonds to neighboring components.
- Environmental check: utilities, media, voids, vibration sensitivity of adjacent structures.
Based on the data, classification follows by:
- Material type and strength (concrete, rock, masonry, mixed zones)
- Structure (stratification, joints, crack network, reinforcement ratio)
- Boundary conditions (access, supports, moisture, temperature)
- Protection goals (vibration, noise, dust, component preservation)
- Method selection and tool configuration
Tool selection and methods depending on the subsoil
- Massive, lightly reinforced concrete: rock and concrete splitters with a defined drilling pattern; hydraulic power packs from Darda GmbH deliver reproducible splitting forces.
- Densely reinforced reinforced concrete: concrete demolition shears for controlled crushing and cutting through concrete cross-sections; for larger cross-sections, combine with pre-cuts or core drilling.
- Rock with pronounced joints: hydraulic wedge splitter utilize existing weakness zones to release blocks; set borehole spacings along the joint orientation.
- Masonry with heterogeneous structure: shears with adapted cutting geometry and moderate hydraulic pressures for joint-oriented removal.
- Steel content and built-ins: separate bars and sections with steel shears or combination shears; then remove residual concrete using shear- or splitting-based methods.
- Special operations with vessels and tanks in sensitive environments: tank cutters for vessel walls; secure the subsoil (foundations, supports) in advance and plan load transfer.
- Complex separation tasks: Multi Cutters for changing material interfaces; account for subsoil changes early in the work sequence.
Planning, safety, and legal framework
Safe work on the subsoil requires a hazard assessment, suitable protective measures, and robust work planning. Permits, traffic safety, and neighbor protection must be considered depending on project and location. Codes and recognized rules of practice must be observed; if in doubt, obtain expert advice.
- Structural stability: plan temporary shoring and decoupling, monitor load paths.
- Vibration and noise control: adapt methods and parameters (pressure, blow rate, splitting sequence) to sensitive environments.
- Dust and water management: wetting, extraction, controlled water handling during drilling and splitting.
- Utilities and hazardous substances: locate lines, depressurize media, mark contaminated areas.
- Workplace design: non-slip, load-bearing supports for machines; keep escape routes clear.
Execution: step-by-step for splitting- and shear-based methods
- Capture the subsoil: check material, reinforcement, joint/crack pattern, moisture, and supports.
- Sectioning: set separation cuts, decoupling, and shoring.
- Define the drilling pattern (for splitting methods): select diameter, depth, spacings according to the material and target fracture line.
- Splitting: deploy rock and concrete splitters or hydraulic wedge splitter, increase hydraulic pressure in a controlled manner, observe crack propagation.
- Crushing: apply concrete demolition shears, reduce cross-sections; separate reinforcement with steel shears or combination shears.
- Finishing: trim edges, relieve residual stresses, secure components, and transport them away.
- Quality assurance: inspect the fracture pattern, verify dimensional accuracy, and continue documentation.
Influence of moisture, temperature, and season
Moisture increases the ductility of many construction materials and can affect splitting tensile strength. Frost leads to brittleness and can promote uncontrolled spalling. Hydraulic components must be operated within their intended temperature windows; in cold conditions, increase starting pressures gently. Wet subsoils require non-slip supports and adapted dust and water handling.
Low-vibration methods in tunnel construction and sensitive areas
In tunnel construction, hospitals, or densely built-up inner cities, low vibration and noise levels are essential. Mechanical splitting with rock and concrete splitters and controlled crushing with concrete demolition shears enable low vibration input into the subsoil. The sequence of load redistributions must be planned to avoid settlements and crack propagation in adjacent components.
Practical examples from the fields of application
Concrete foundation in inner-city deconstruction
A massive foundation with low reinforcement is divided into sections. Core drilling defines the split line, rock and concrete splitters generate the fracture. Edges are finished with concrete demolition shears to protect adjoining components.
Rock removal in tunnel heading
Jointed rock with clear bedding orientation: boreholes along the benches, hydraulic wedge splitter release blocks in a controlled manner. The low vibration protects the lining and the surroundings.
Natural stone extraction
Massive natural stone bench: splitting spacings according to grain fabric and joint spacing. Hydraulic splitting reduces microcrack formation and delivers dimensionally accurate blocks for further processing.
Typical mistakes and how to avoid them
- Underestimated reinforcement: locate in advance; for high density, plan with concrete demolition shears and steel shears.
- Incorrect drilling pattern: adjust spacings to strength and joint system; tie depth to the target fracture plane.
- Insufficient support: provide load-bearing supports; monitor load redistributions.
- Ignoring moisture and temperature effects: adjust parameters, pressure stages, and sequence of steps.
- Unclear sectioning: set separation cuts and decoupling early to avoid uncontrolled fractures.
Key parameters and terms for subsoil assessment
- Compressive strength, tensile and splitting tensile strength
- Reinforcement cover, reinforcement ratio
- Joint spacing, joint continuity, layer thickness
- Porosity, moisture content, carbonation depth
- Support conditions, bond and boundary conditions