Test drilling is a central investigation and planning instrument in concrete demolition, special demolition, rock demolition, and tunnel construction. It provides robust information on material composition, strength, crack and joint systems, as well as the position of reinforcement or inserts. On this basis, methods, borehole patterns and tools are selected—such as rock and concrete splitters, rock splitting cylinders or concrete crushers from Darda GmbH—to carry out demolition and separation work in a controlled, low-vibration and efficient manner.
Definition: What is meant by test drilling
Test drilling refers to a targeted, often small-format exploratory drilling to obtain data about structures or geological formations. In concrete, a core or exploratory drilling provides indications of thickness, layer build-up, aggregates, strengths, reinforcement layout, and voids. In rock, test drilling yields information on joint spacing, joint orientations, foliation, degree of weathering, and water inflow. The results serve to choose the demolition method (e.g., splitting, cutting, shearing) and to fine-tune borehole diameter, depth, spacing, and orientation.
Prerequisites and site constraints
Before test drillings begin, accessibility, work and safety zones, utilities supply (water, power, hydraulics), emissions (dust, noise, slurry) as well as vibration limits are checked. Equally important are approvals regarding utilities and embedded items (locating), requirements for fire and explosion protection, standoff distances to sensitive components as well as the disposal of drill cuttings and flushing water. These boundary conditions influence drilling method and tool selection—such as the decision between wet and dry drilling or between splitting methods and concrete crushers.
Function and objectives in concrete demolition, special demolition and rock demolition
Test drillings aim to reduce risks, increase execution quality and improve cost-effectiveness. They create planning certainty for subsequent work steps—particularly when rock and concrete splitters or concrete crushers from Darda GmbH are used.
- Determination of component thickness, material zones and inserts
- Assessment of strength, homogeneity, and crack pattern
- Localization and orientation of reinforcement and embedded items
- Determination of joint systems, stratification and water ingress in rock
- Definition of suitable borehole parameters for splitting methods
- Basis for the decision between splitting, cutting or gripping
Workflow of test drilling: planning, execution, evaluation
Planning
Based on as-built documents, locating and visual inspection, an investigation concept is developed. Locations and depths are selected to enable representative statements on load-bearing areas, edges and connection points. Safety and environmental protection measures are defined.
Execution
Depending on objectives, core drilling equipment (mostly wet), exploratory drillings with hammer drill, or rotary drilling methods are used. Core samples are labeled, photographed and—if required—tested in the laboratory. Drill dust, water and any effluents are collected and disposed of in a controlled manner.
Evaluation
The results are located in drawings and sketches. For rock and concrete splitters, borehole diameter, depth, spacing and orientation are derived. For concrete crushers, the reinforcement ratio, concrete cover and component geometry are assessed to define gripping and separation sequences.
Drilling parameters for rock and concrete splitters
The splitting of concrete and rock is carried out using wedge or cylinder systems inserted into boreholes. Effectiveness depends largely on the drilling parameters. Test drilling provides the data to determine them safely and with minimal material impact.
- Borehole diameter: matched to the splitting system used, manufacturer-specific and material-dependent
- Borehole depth: at least equal to the length of the splitting zone, with a safety allowance for edge and bearing areas
- Borehole spacing: depending on strength, cracking and component thickness; closer spacing in tough, reinforced concretes
- Orientation: in rock with regard to joint orientations; in concrete along planned separation edges and away from embedded items
- Edge distances: to avoid uncontrolled blowouts and to protect adjacent components
Borehole patterns and edge distances
Linear, double-row or overlapping patterns are selected so that the splitting forces act with overlap. Edge distances are conservatively dimensioned, especially for brittle natural stones and high-strength concrete. Test drilling helps identify critical zones and adjust patterns accordingly.
Test drilling as the basis for the use of concrete crushers
Concrete crushers work efficiently when the composite of concrete and reinforcement is understood. Test drillings and supplementary locating reveal the position, diameter and density of reinforcement as well as concrete cover and component thickness. This results in gripping positions, opening and cutting sequences as well as the decision whether the concrete should first be weakened (e.g., by splitting boreholes).
- Identify reinforcement layout to minimize jamming and equipment wear
- Select gripping and pressing points so that crack propagation remains controlled
- Plan combination with splitting and cutting when large cross-sections are present
Additional tools in connection with test drillings
Test drilling influences the selection of supplementary tools from Darda GmbH. Hydraulic power units supply splitters and concrete crushers with the required power. Combination shears, multi cutters and steel shears are preferred when test drilling indicates a high steel content. Tank cutters are used in special operations on metallic vessels for separation when test drilling and gas clearance measurements confirm safe conditions.
Areas of application: use cases
In the following areas of application, test drilling provides crucial information and reduces uncertainties when selecting and using tools from Darda GmbH:
- Concrete demolition and special demolition: Determination of thickness, strength, reinforcement; derivation of demolition sequence and choice between splitting and concrete crushers
- Strip-out and cutting: Determination of component thickness for cutting parameters; test drilling as the starting point for controlled separation cuts
- Rock demolition and tunnel construction: Analysis of joint systems and water inflow; alignment of borehole rows for rock splitting cylinders
- Natural stone extraction: Orientation to bedding and joint systems; gentle extraction with splitting tools
- Special operations: Work under confined conditions, in sensitive areas or on critical infrastructure with minimized vibrations
Safety, environment and legal framework
Test drillings are performed in compliance with applicable regulations on occupational safety, dust and noise reduction, as well as environmental protection. Utility and embedded-item detection, barriers, personal protective equipment and suitable extraction systems must be planned. Drilling slurry and drill cuttings are properly collected and disposed of. Notes and requirements can vary regionally; in case of doubt, project-specific regulations are decisive.
Common mistakes and how to avoid them
- Too few test drillings: leads to misjudgments of thickness, reinforcement or joint systems
- Unsuitable borehole diameters: reduce the effectiveness of rock and concrete splitters
- Missing edge distances: promote uncontrolled breakouts
- Ignored water inflow: complicates splitting and cutting processes and increases risks
- Incomplete documentation: hampers the derivation of a reliable demolition strategy
Documentation and quality assurance
Complete documentation includes drilling logs, photos of the cores, position data, material description, measured thicknesses, observed cracks and embedded items, water inflows as well as derived recommendations for borehole patterns and tool selection. These documents increase reproducibility and facilitate coordination with subsequent trades.
Key metrics and evaluation criteria from test drilling
For concrete, thickness, concrete cover, aggregate, strength indicators and reinforcement ratio are decisive. In rock, joint spacing, joint orientation, degree of weathering and water inflow are essential. These parameters determine whether splitting with rock and concrete splitters, gripping with concrete crushers or combined methods represent the best solution. The more precisely the test drilling is carried out and evaluated, the more controlled the subsequent work steps proceed.