The bored pile foundation ranks among the most important foundation and retaining systems in building construction and structural/civil engineering. It transfers structural loads via shaft friction and/or pile toe resistance into competent soil layers and, in the form of bored pile walls, provides secure excavation pit cut-offs. Over a structure’s life cycle there are numerous touchpoints with concrete demolition and special demolition: during pile head preparation, when creating openings or partially dismantling bored pile walls, and during alterations in existing structures. Depending on the boundary conditions, low-vibration methods such as concrete demolition shears or stone and concrete splitters from Darda GmbH are used, supported by suitable hydraulic power packs and cutting tools for the reinforcement.
Definition: What is meant by a bored pile foundation
A bored pile foundation is a cylindrical foundation element made in the ground from concrete or reinforced concrete, constructed by drilling and equipped with reinforcement. After drilling out, the pile—depending on the method—is stabilized by support fluid or a casing pipe, fitted with a reinforcement cage, and subsequently concreted. Bored piles are executed as single piles or in groups for foundations, as well as as tangent, partially overlapping, or secant pile walls for excavation pits, tunnel portals, shafts, and slope stabilizations.
Configuration, construction, and variants of bored piles
The typical configuration comprises the pile toe, the cylindrical shaft, and the pile head. Load-bearing action results from shaft friction and toe resistance. Construction method and geometry are adapted to the geotechnical conditions to limit settlements and ensure the required bearing capacity over the long term.
Construction methods
- Kelly drilling: Dry or with casing/support fluid; suitable for heterogeneous soils and larger diameters.
- Continuous flight auger (CFA): Continuous concreting through the hollow stem; economical in soft to medium-stiff soils.
- Full-displacement method: Soil displacement with minimal spoil; limited use in densely compacted soils.
- Cased drilling or support fluid: To stabilize the borehole wall in non-cohesive or unstable layers.
Geometry and materials
- Diameters typically 0.60–1.50 m (project-dependent variations possible), lengths often 10–40 m or more.
- Concrete with sufficient workability and durability; reinforcement cages designed for bending moments and shear.
- Optional pile base enlargement or injections to increase toe resistance.
Bored pile walls: execution and use
Bored pile walls secure excavation pits, tunnel portals, and shafts. Tangent piles are closely spaced in sequence, overlapping piles interlock and create a relatively tight wall, and secant piles overlap to form a continuous barrier. Execution may be single-row or multi-row, with intermediate infill panels or a shotcrete facing.
Sealing and bracing
Depending on groundwater and soil conditions, the wall may require additional sealing. Anchors, bracing frames, or cover slab methods secure the temporary condition. Profiling the pile head and forming a ring beam are essential for load redistribution.
Interfaces with demolition, deconstruction, and adaptations
In new construction and existing structures, precise, low-vibration processing of bored piles is required—particularly in urban environments, near sensitive neighboring buildings, or in facilities that remain in operation. Methods based on controlled breaking, splitting, and cutting are well-suited.
Pile head preparation (pile head trimming)
After concreting, the pile head is exposed to a defined elevation. Instead of percussive methods, concrete demolition shears are often used to crush the concrete cover in a controlled manner. Stone and concrete splitters can be used additionally to induce targeted cracks, expose the reinforcement, and create the head geometry with negligible vibration. The reinforcement is then cut to size with combination shears or steel shears.
Openings and breakthroughs in bored pile walls
Openings are formed in bored pile walls for service crossings, doors, or temporary access. Concrete demolition shears enable selective removal of the concrete portions, while combination shears or Multi Cutters sever the reinforcement, anchor heads, and embedded items. Stone and concrete splitters help relieve cut edges and steer breakage in a controlled manner.
Selective deconstruction in existing structures
Where bored piles are to be partially removed, shortened, or exposed—e.g., for foundation strengthening, conversions, or utility adjustments—splitting and shear-based methods allow finely dosed intervention. This is crucial for concrete demolition and special demolition in inner-city contexts to minimize vibration, noise, and dust.
Tool selection in the context of bored pile foundations
The choice of carrier-mounted and handheld tools depends on concrete strength, degree of reinforcement, accessibility, and requirements for vibration and noise control. Relevant solutions from the Darda GmbH portfolio are combined as needed.
- Concrete demolition shears: For low-vibration crushing of pile heads, upstands, ring beams, and infill; also suitable for fair-faced concrete surfaces on bored pile walls when a defined removal is required.
- Stone and concrete splitters as well as stone splitting cylinders: For introducing controlled cracks after core drilling or hammer drilling; effective on heavily reinforced pile heads, on massive heads of secant piles, and where space is limited.
- Combination shears and steel shears: For cutting longitudinal and stirrup reinforcement, anchor strands, girder profiles in capping beams, and steel components that couple piles.
- Multi Cutters: For cables, light reinforcement, and auxiliary structures during exposure.
- Tank cutters: For special operations involving steel tanks or hollow sections in the immediate vicinity of bored piles; the cutting path must be adapted to fire and spark protection.
- Hydraulic power packs: For reliable, mobile power supply to the tools—important where electrical power is limited in the excavation pit or tunnel area.
Application areas and typical project constellations
Bored piles are encountered in numerous projects: from high-rise foundations to infrastructure works and underpinning in existing buildings. In all these scenarios there are touchpoints with the application areas of Darda GmbH.
- Concrete demolition and special demolition: Pile head preparation, adjustment of capping beams, openings in bored pile walls.
- Strip-out and cutting: Selective removal in existing excavation pits, freeing reinforcement and anchors.
- Rock excavation and tunnel construction: Combination of bored pile walls at portals/shafts and rock loosening by splitting techniques.
- Natural stone extraction: Transferable splitting methods in rock; know-how in controlled brittle-fracture processes also supports work on piles.
- Special operations: Work under tight, sensitive, or emission-critical conditions with remotely operated, hydraulic tools.
Vibrations, noise, and neighbor protection
City centers, hospitals, laboratories, or listed monuments demand low emissions. Methods using concrete demolition shears and stone and concrete splitters reduce vibration markedly compared with percussive techniques. Short tool paths, a planned removal grid, and cutting the reinforcement with combination shears minimize side effects such as cracks in neighboring buildings or settlements due to dynamic actions.
Quality assurance and testing
For the bearing capacity of bored piles, load tests, integrity tests, and documentation of concreting are essential building blocks. During pile head trimming and deconstruction, defined cut edges, recompaction of remaining concrete surfaces, and clean exposure of the reinforcement ensure connection quality. References to standards and guidelines must be considered project-specifically; legal requirements and responsibilities should be clarified in the planning stage.
Planning, logistics, and occupational safety
The construction sequence benefits from early coordination between special foundation engineering, shell construction, and deconstruction teams. Access routes, load take-up, utility supply, and waste disposal logistics must be defined in advance. Hydraulic power packs are positioned so that exhaust gases, noise, and hoses do not conflict with escape and rescue routes. Personal protective equipment, fall protection, and checking pressure lines are mandatory.
Material separation and disposal
Clean separation of concrete and reinforcing steel facilitates recycling and disposal. Steel shears and Multi Cutters support downsizing and sorting of metal fractions, while concrete demolition shears process the concrete portion into grain-appropriate fractions.
Typical defect patterns and remediation
Local deficiencies such as honeycombing, insufficient cover, or voids at the pile surface can be repaired in a targeted manner. Damaged concrete is removed with concrete demolition shears or by splitting until sound core concrete is exposed. Repair then follows using suitable mortars/concrete and reworking of the pile head. If the pile head is insufficient, supplementary reinforcement can be exposed and extended to achieve full bond; cutting and shaping of the reinforcement is carried out with combination shears and steel shears.
Bored pile foundation in tunnel and shaft construction
Bored pile walls secure tunnel portals, access shafts, and excavation pits in rock and in soft ground. The combination of piles and rock removal requires precise work. Stone and concrete splitters relieve rock edges and pile connections, while concrete demolition shears selectively adapt concrete support structures. Controlled separation of anchors, sheet-pile connections, or temporary steel structures is performed with steel shears and combination shears.
Sustainability and resource efficiency
Low-vibration, energy-efficient methods reduce environmental impact. Selective deconstruction with concrete demolition shears and targeted splitting minimize material losses and facilitate recycling. Separate collection of concrete and steel reduces disposal efforts and conserves resources.
Distinction from other pile construction methods
In addition to bored pile foundations there are driven piles, micropiles, and displacement piles. The choice depends on subsoil, loads, and context. Regardless of the type, where piles need to be adapted, shortened, or locally opened, low-vibration methods with concrete demolition shears, stone and concrete splitters, and suitable cutting tools are a robust option—especially in sensitive environments.