The pilot borehole is a central procedure to prepare interventions in concrete and rock precisely, in a controlled manner, and with predictable quality. Whether in concrete demolition and special demolition, in rock excavation for tunnel construction, or in natural stone extraction: An exactly guided borehole defines the subsequent separation joint, directs forces, and reduces unwanted cracking. This creates the basis for the efficient use of rock and concrete splitters, concrete demolition shear, as well as complementary tools from Darda GmbH such as hydraulic power units, combination shears, rock wedge splitter cylinders, Multi Cutters, steel shear, and tank cutters.
Definition: What is meant by a pilot borehole
A pilot borehole is a purposefully aligned, dimensionally accurate borehole that maintains position, direction, and depth so that material can be separated or further processed in a controlled way. It is used to create a drilling pattern, prescribe separation lines, provide insertion openings for wedge splitter cylinders, or define cutting edges for concrete demolition shear. Typical characteristics are straight and parallel alignments, defined spacings in the drilling pattern, and a depth matched to the planned separation joint. The pilot borehole is thus both a prerequisite and a guide for subsequent work steps in concrete and rock removal.
Classification and purpose of the pilot borehole within demolition and extraction
The pilot borehole forms the interface between planning and execution. It links structural requirements, material properties, and the selected separation method. In combination with rock and concrete splitters, it creates defined stress fields that promote the desired fracture along the prescribed line. For concrete demolition shear, it marks areas in which the component is preloaded or weakened, allowing the jaws to be applied in a targeted manner and the reinforcement to be subsequently separated. The result is reproducible outcomes with reduced vibrations, lower noise emissions, and improved component control.
Geometry of the pilot borehole: drilling pattern, tolerances, and accuracy
Dimensional accuracy is the key to effectiveness. The drilling pattern—i.e., diameter, center distances, depth, and alignment—is adapted to the material, the component geometry, and the follow-on tool. Deviations in inclination or offset can deflect fractures or diminish the effect of a rock wedge splitter cylinder. In concrete, aggregates and reinforcement influence the course, while in rock, bedding, jointing, and moisture must be considered. The more homogeneous the matrix, the more uniform the force distribution during splitting or gripping.
Diameter, depth, and center offset
The borehole diameter is determined by the device to be used: rock and concrete splitters and wedge splitter cylinders require matched diameters and minimum depths so that spreading wedges or cylinders can act over their full surface. The depth determines the height of the separation joint and the fracture path. Low center offset in the drilling pattern improves the linear guidance of the fracture and reduces rework.
Substrate and material behavior
In reinforced concrete, reinforcement must be detected and—if the goal is an application with concrete demolition shear—selectively exposed or avoided. In natural stone and rock, natural discontinuities influence the drilling direction. Preliminary investigation, test drilling, and adjustment of rotational speed/feed forces increase process reliability.
Tools, drive technology, and process chain
In practice, pilot boreholes are produced with a core drilling rig or heavy percussion hammers. The choice depends on material thickness, required accuracy, and the subsequent method. A well-matched interaction with hydraulic power units from Darda GmbH is particularly relevant when rock and concrete splitters, wedge splitter cylinders, or concrete demolition shear are used afterwards. In the process chain, combination shears, Multi Cutters, steel shear, or tank cutters can follow the splitting step to reduce dimensions, cut reinforcement, and separate elements by material type.
Application fields of the pilot borehole
In concrete demolition and special demolition, the pilot borehole enables controlled separations near sensitive structures, for example at extensions, bridge parapet caps, or foundation edges. For concrete demolition shear, it creates defined attack points that facilitate gripping and breaking. In building gutting and cutting, targeted boreholes are used to guide cuts, pick up loads, and release components section by section. In rock excavation and tunnel construction, the pilot borehole defines the contour of excavations; rock and concrete splitters act along the drilling lines to avoid overbreak and keep vibrations low. In natural stone extraction, the pilot borehole defines the later raw block geometry and provides insertion openings for wedge splitter cylinders. In special assignments—e.g., in noise-sensitive zones—it supports particularly low-vibration methods and precise sequencing of subtasks.
Pilot borehole for rock and concrete splitters
The splitting mechanism relies on concentrated tensile stress along a prescribed line. The pilot borehole defines this line. Spacings that are too narrow or too wide, unsuitable depths, or inaccurate inclinations weaken the effect. In practice, boreholes are positioned so that the splitting wedges or the pistons of a wedge splitter cylinder achieve maximum leverage. Hydraulic power units supply the devices consistently, generating uniform forces and keeping the fracture controllable. The result is clean separation joints that speed up rework with concrete demolition shear or combination shears.
Pilot borehole for concrete demolition shear
Concrete demolition shear work particularly efficiently when components are notched or weakened beforehand. Pilot boreholes can aid fracture initiation, selectively shift stresses, and define jaw attack points. In reinforced components, suitable drilling patterns can create areas in which the concrete matrix breaks faster, while reinforcing steel bars are then separated with steel shear or Multi Cutters. This approach reduces uncontrolled spalling, shortens cycle times, and protects adjacent components.
Planning and execution: workflow from concept to separation joint
Planning starts with defining the objective: Which joint, which block, which dimensions are required? This is followed by material analysis, accessibility checks, and selection of the drilling system. The drilling pattern is defined so that the subsequently used rock and concrete splitters or concrete demolition shear can act optimally. During execution, rotational speed, feed, tool service life, and cooling (for core drilling) must be monitored. Removal of drillings, clean hole edges, and documented depths increase reproducibility. Finally, controlled separation is performed, followed by dimensional correction with suitable shears if required.
Quality assurance and documentation
Key inspection points are hole diameter, depth, center offset, and inclination. Simple measuring tools or drilling gauges are often sufficient; for critical components, measurement records with reference points are advisable. Photographic documentation of the drilling pattern facilitates evaluation of the fracture path and optimization for subsequent sections.
Safety and environmental aspects
Occupational safety begins with securing the equipment, appropriate protective clothing, and orderly routing of the hydraulic hose line from the hydraulic power unit. Dust and noise reduction—e.g., through wet drilling or extraction—protects personnel and surroundings. Low-vibration separation methods—especially in combination with rock and concrete splitters—are advantageous in sensitive areas. Legal requirements must be considered depending on location and project.
Selection criteria: drilling strategy and equipment compatibility
Compatibility between borehole and subsequent tool is crucial: Diameter and depth must match the specific wedge splitter cylinder or splitting system, and the joint line must suit the expected load transfer and component structural analysis. For concrete demolition shear, upfront planning that considers reinforcement layout, concrete cover, and jaw opening is advisable. In massive components, a two-stage approach—splitting first, then shear work—can be the most effective solution.
Terminology and delineation
The pilot borehole differs from general drilling in that it assumes a guiding function for subsequent removal. Related methods include test boreholes (for exploration), contour or umbrella boreholes (for line guiding in rock), as well as core drilling (for precise openings). While these techniques pursue different goals, the pilot borehole shares the core principle of targeted alignment and dimensional accuracy—with the focus on providing subsequent devices such as rock and concrete splitters or concrete demolition shear with a defined, controlled working basis.
Application examples and typical drilling scenarios
In bridge deconstruction, pilot boreholes can be placed along the inner edge of the parapet cap to decouple subsequent splitting and shear work from the roadway. In tunnels, a contour-true drilling pattern marks the excavation limit; targeted splitting prevents overbreak and protects the lining. In natural stone extraction, a series of parallel boreholes defines the future block edge so that wedge splitter cylinders can release the raw block along the planned plane. In massive foundations, a tuned drilling pattern enables predictable segmentation that concrete demolition shear and combination shears can rework quickly. In facilities with sensitive periphery—such as special assignments—precise pilot boreholes enable a low-noise, low-vibration separation strategy with high dimensional accuracy.