Casing pipe

The casing pipe is a central component in borehole drilling and deconstruction technology. It stabilizes boreholes, protects utilities and embedded components, and creates defined interfaces between subsoil, concrete, and tools. In conjunction with the product groups from Darda GmbH – such as rock and concrete splitters, concrete demolition shears, steel shears, or hydraulic power packs – suitable casing often determines precision, safety, and efficiency in concrete demolition, selective deconstruction, rock excavation, and tunnel construction. When correctly dimensioned and handled, casing also reduces rework, extends tool life, and enables low-emission workflows in confined or sensitive environments.

Definition: What is meant by a casing pipe?

A casing pipe is a housing or sleeving element that, as an outer shell, encloses a borehole, a penetration, or a line to be protected. It serves the stabilization and separation of materials (e.g., soil/concrete), the guidance of tools and media, and protection against actions such as earth or concrete pressure. Depending on the application, the casing pipe is installed temporarily and then extracted (borehole casing) or left in place permanently as a protection pipe, liner pipe, or sleeve. Common materials include steel, ductile cast iron, GFRP, and HDPE. Diameter, wall thickness, and the connection system (e.g., sockets, threads) are selected according to the drilling method, loads, and the intended deconstruction or installation. In safety-relevant applications, verification of load transfer and sealing performance is required; sizing considers axial and radial loads as well as thermal and chemical influences.

Design, materials, and typical dimensions

Casing pipes consist of cylindrical pipe segments with defined inner and outer diameters. For steel pipes, wall thicknesses are designed for ring stiffness and buckling and denting resistance, often with screw or push-fit sockets as detachable connectors. Plastics such as HDPE offer chemical resistance and low weight; GFRP combines corrosion resistance with high stiffness. Typical nominal diameters range – depending on the application – from small sleeves for service penetrations (e.g., DN 50-150) to large-format drilling casing for rock and tunnel advances (in the range of several hundred millimeters). Complementary components can include centralizers, wipers, sealing cuffs, or cutting crowns. For permanent installation, surface protection, corrosion protection, and the formation of transition zones (e.g., grouting, sleeve sealing) are essential.

• Connection variants: threaded joints, push-fit sockets, quick-lock couplings, and flanged sleeves for detachable assembly
• End configurations: cutting crowns or reinforced edges for active advance, beveled ends for easier penetration
• Surface options: galvanization, coatings, or liners to mitigate corrosion and abrasion in long-term use

Fields of application in concrete demolition, special deconstruction, and rock excavation

In concrete demolition and special deconstruction, the casing pipe often provides safe guidance for core or percussive drilling that is later processed with tools such as concrete demolition shears or rock and concrete splitters. In heterogeneous components (reinforced concrete, masonry, mixed cross-sections), the casing separates the drilling channel from the surrounding material and reduces spalling. In rock excavation and tunnel construction, casing in loose rock or weathered zones enables reaching load-bearing layers to produce boreholes for splitting cylinders or to create controlled preset fracture lines. In strip-out operations, sleeves frequently appear as built-in parts for service penetrations; during exposure and removal, clean separation cuts in concrete and steel are crucial to protect adjacent components. Additional benefits include reduced vibration transmission, improved dust control, and defined interfaces for subsequent sealing or grouting steps.

Casing pipe and rock and concrete splitters

For controlled splitting, the borehole quality is decisive. A cased borehole maintains geometry and diameter, minimizes drilling dust ingress, and prevents loose material from falling in. This facilitates the precise insertion of splitting cylinders and the alignment of crack lines. In deeper boreholes or with changing soil layers, the casing ensures that hydraulic components can be reliably positioned. hydraulic power units from Darda GmbH supply the splitters; reproducible borehole quality improves the repeatability of splitting operations.

• Quality levers: roundness and straightness of the borehole, consistent inner diameter, controlled flushing or air extraction, and precise depth marking
• Operational stability: reduced risk of stuck tools and predictable crack initiation across multiple, parallel boreholes

Casing pipe in combination with concrete demolition shears

Many components contain sleeves or protection pipes for service lines. In selective deconstruction, the surrounding concrete volume is first broken in a controlled manner with concrete demolition shears so that the casing pipes become visible and accessible. The defined separation between concrete and pipe facilitates further deconstruction: pipe segments can then be cut to length with steel shears, combi shears, or multi cutters. This keeps intervention depth minimal and protects adjacent structures – an advantage indoors, during gutting works, or in sensitive existing areas. Where hot work is restricted, mechanical cutting with shears minimizes sparks and heat input.

Planning, selection, and sizing

Selecting a suitable casing pipe follows the technical framework of subsoil, component, and method. The goal is sufficiently stiff, tight-fitting, and tool-compatible casing that can be safely installed and extracted. Key criteria include:

• Geology and component: soil class, water ingress, reinforcement density, existing embedded parts
• Method: core drilling, double-head drilling, overlapping drilling, advance in loose ground
• Geometry: usable inner diameter for splitting cylinders or drill bits, tolerances, ovality
• Mechanics: ring stiffness, bending and buckling stability, abrasion resistance
• Corrosion and chemistry: media compatibility, long-term durability in permanent installation
• Sealing: cuffs, grouting, transitions for penetrations with water- or gas-tightness requirements
• Deconstruction: detachable connections, torque transmission for extraction, minimizing jamming
• Tolerances and quality control: straightness, roundness, surface roughness, and measurable acceptance criteria
• Logistics and handling: segment length, lifting points, transport protection, and on-site assembly sequence

For use with rock and concrete splitters, diameters and borehole depth should be chosen so that setting and centering of the cylinders proceed smoothly. For components with sleeves, it is advisable to plan cutting and breaking sequences so that pipe bodies are only separated after the surrounding concrete has been relieved. Early coordination of tool interfaces and sealing requirements prevents rework and supports predictable project timelines.

Installation, casing techniques, and deconstruction

Various casing techniques are used in practice. With rotary-percussive drilling, the casing is advanced section by section. Double-head drilling transmits torque separately to the drill string and the pipe, so the casing is actively driven forward. In loose ground, casing pipes secure the borehole against collapse; in concrete, they protect edges and reinforcement and retain drilling dust in the process. After completion, temporary pipes are extracted by torque and tensile forces; permanently retained pipes receive grouting or sealing systems. In deconstruction, exposed steel casing pipes are cut with steel shears or combi shears. For tanks and large-format shells, tank cutters can be used; the selection and sequence of cuts are based on component stiffness, residual stresses, and emission control.

1. Survey and marking of boreholes and utilities
2. Pilot drilling and initial casing insertion with centralizers
3. Sectional advance with controlled torque and flushing strategy
4. Verification of depth, straightness, and inner diameter before tool use
5. Extraction of temporary casing or installation of sealing and grout systems
6. Stepwise deconstruction of exposed pipes aligned with static and emission constraints

Safety and environmental protection

Safety aspects particularly involve preventing borehole collapses, uncontrolled spalling, and unintended material movements. Personal protective equipment, low-dust methods, controlled splitting and cutting management, and careful location detection of utilities and reinforcement are essential. Separate requirements apply to water- or gas-tight penetrations regarding sealing and grouting. It is advisable to consult recognized rules of the art and relevant bulletins and obtain project-specific approvals.

• Process controls: torque and thrust monitoring, continuous extraction checks, and documentation of borehole parameters
• Environmental measures: dust and slurry capture, noise reduction, and proper disposal of cuttings and residues

Typical challenges and damage patterns

In casing practice, jamming, ovalization, bore channel enlargement, or unexpected layer changes can occur. Jamming is promoted by high friction, infiltrated cuttings, and local deformations; remedies include cleaned boreholes, suitable lubrication or flushing concepts, and adequately dimensioned tensile and torque capacities. In heavily reinforced concrete, casing pipes can snag on reinforcement; precise location detection and pilot drilling reduce this risk. For splitting work, a consistent borehole geometry is critical: deviations impair spread paths and crack formation. When working around existing sleeves in the structure, notch effects must be avoided; concrete demolition shears enable stepwise, edge-close breaking before steel shells are separated.

• Early indicators: rising torque, reduced advance per revolution, and increased vibration signal friction or misalignment
• Countermeasures: intermediate cleaning, temporary reaming, or adjusting segment length and connector friction

Practice: tunneling, natural stone extraction, and special applications

In tunneling, casing pipes stabilize pilot and relief boreholes at the tunnel face to enable controlled advance measures. After reaching load-bearing zones, boreholes for rock splitting cylinders are drilled and defined separation cracks are created. In natural stone extraction, a cased borehole reduces the influence of brittle overburden layers and facilitates subsequent splitting along desired joints. Special applications – such as in narrow shafts or vibration-sensitive buildings – benefit from cased, low-emission drilling and a sequential approach: first controlled breaking of the concrete with concrete demolition shears, then cutting of the sleeves with suitable cutting tools. In all cases, alignment and spacing of cased boreholes determine crack propagation and efficiency of subsequent operations.

Terminology and related types

In practice, casing pipe, sleeve, protection pipe, drill pipe, and liner pipe are sometimes used differently and sometimes synonymously. In the narrower sense, the casing pipe surrounds an opening or a medium, while the drill pipe is guided temporarily during drilling and the liner pipe often remains permanently. Protection pipes in concrete primarily provide separation and protection of service lines; drilling casing secures the process. Regardless of the designation, the function remains similar: stabilize, separate, guide – thus creating the preconditions for precise splitting, cutting, and demolition with the product groups of Darda GmbH. A consistent casing strategy across planning, execution, and deconstruction reduces risk and enhances reproducibility in demanding site conditions.