A thrust pipe is a central component in trenchless pipeline construction and tunnel heading. It transmits axial forces, protects bores, and enables the advancement of pipelines beneath roads, rail tracks, and structures. Over the life cycle of a thrust pipe—from planning and installation to repair or deconstruction—classical engineering disciplines meet practical demolition and separation techniques. Especially when working in existing structures or shafts, precise, low-vibration methods are important. These include, among others, controlled concrete removal with concrete demolition shears as well as powerful yet low-shock splitting with hydraulic rock and concrete splitters, as used in the environment of Darda GmbH.
Definition: What is meant by thrust pipe
A thrust pipe is a pipe that, in pipe jacking, transfers the jacking forces introduced by the jacking frame to subsequent pipe strings. Thrust pipes are often made of reinforced concrete or steel and are used as jacking pipes, casing pipes, or sheathing pipes, depending on their function as load-bearing, protective, or media pipe. They are characterized by design for high longitudinal compressive forces, ring-shaped soil pressures, and—depending on the method—bending moments. Connections are usually made via spigot/socket with sealing systems, or via flanges for steel pipes. In operation, thrust pipes either serve permanently as a pipeline or temporarily as a protective and working pipe that remains after completion of the measure or is deconstructed.
Design, materials, and interfaces
The structural design depends on the method, geology, and service life. Reinforced-concrete thrust pipes have a reinforced shell with an integral socket, steel thrust pipes a welded shell with annular stiffeners. The end geometry (socket/spigot or flange) ensures force transfer and watertightness. For the jacking process, external surfaces are often wetted with lubricants (e.g., bentonite) to reduce friction.
Sealing systems and joints
Seals ensure watertightness at the pipe joints. Common are positive- and friction-locking sealing systems with elastomer sealing profiles. With steel pipes, bolted or welded joints are used; temporary working joints can additionally be secured with clamping rings to reliably introduce the jacking forces.
Materials and surfaces
- Reinforced concrete: robust ring stiffness, good load distribution, proven in municipal pipeline construction.
- Steel: high tensile/compressive strength, good weldability, preferred for high longitudinal loads or as a temporary casing pipe.
- Surface protection: galvanized, coated, or with corrosion protection systems, depending on medium and soil chemistry.
Use in pipe jacking and tunneling
Thrust pipes are jacked into the ground from the launch shaft in Microtunneling and guided pipe jacking. The jacking frame transfers the thrust to the last installed pipe; intermediate jacking stations extend the reach. Lubrication and support slurries reduce friction and stabilize the tunnel face. In rock excavation and tunnel construction, steel pipes often serve as casing pipes for core drilling or as protective pipes when jacking beneath sensitive structures.
Shaft logistics
Work in launch and reception shafts is characterized by confined space. Adjustment work at the pipe socket, opening recesses, or removing defects require compact, hand-held tools. Concrete demolition shears enable controlled concrete removal without impact loading on the surroundings; rock and concrete splitters create defined crack paths, for example to open shafts or to relieve jammed pipe joints.
Loads, design, and typical damage patterns
- Axial compression: transfer of jacking forces through the joint and shell.
- Ring compression: soil pressures and traffic loads acting above the pipe.
- Bending/eccentricity: direction changes, curves, and local settlements.
- Abrasion: friction against soil, actions from flushing and support slurries.
- Temperature/chemistry: media and soil chemistry, thermal expansions.
Damage and their causes
- Spalling at socket edges due to eccentricity or localized overload.
- Cracks in the shell due to uneven bedding or joint misalignment.
- Seal damage with infiltration/exfiltration in case of assembly or settlement issues.
- Corrosion on steel pipes with damaged corrosion protection or in aggressive environments.
Repair, rehabilitation, and deconstruction of thrust pipes
Depending on the damage pattern, internal linings, partial repairs, or selective deconstruction are used. In existing structures, shafts, and confined pipe corridors, low-vibration, precise methods are advantageous to protect adjacent structures and avoid settlements.
Procedure in confined existing conditions
- Create access: expose the pipe environment section by section, secure against soil and water ingress.
- Concrete removal: locally open recesses and remove projecting edges with concrete demolition shears for good crack control.
- Controlled splitting: drill small holes and expand with rock and concrete splitters to create predetermined separation lines and deliberately reduce component stresses.
- Cutting the reinforcement: after exposing steel components, cut with combination shears or steel shears to separate reinforcement, armoring, or steel jackets.
- Finishing work: break edges, level surfaces, prepare sealing faces; if required, perform another trial fit of the joint components.
- Documentation: visual inspection, measurement log of openings, proof of sealing face quality.
Hydraulic power packs are positioned outside the immediate work area to reduce emissions and ease the burden on operators. Flexible hose bundles allow tool supply in shafts and pipelines.
Occupational safety and environmental protection
In the vicinity of pipelines and shafts, protection of people, structures, and the environment is paramount. Low-vibration methods reduce the risk of crack formation and impacts on sensitive neighboring structures. Notes are always of a general nature and do not replace an object-specific hazard analysis.
- Vibration/noise: hydraulic shears and splitting technology reduce impact and structure-borne noise compared to impact tools.
- Dust: localized misting or water spraying at the point of attack improves air quality.
- Media and soil protection: drip trays for flushing and cutting fluids, orderly disposal of concrete and steel waste.
- Low-conflict workflows: sectional processing, defined quiet phases, monitoring at sensitive structures.
Special application cases in special foundation engineering
Thrust pipes serve as temporary casing pipes for utility crossings, as protective pipes for guided drillings, or as working pipes for installation and removal measures. In rehabilitation scenarios, internal fittings and connections can be adapted or removed.
Blocked or deformed pipes
If jamming or deformation occurs, local pipe stresses are reduced. A proven approach is the combination of core drilling and subsequent splitting to form controlled separation joints. Exposed reinforcement is cut with combination shears or steel shears; for steel jackets, sectional cutting with shears is expedient. This allows clamped pipe segments to be relieved without excessively stressing the surroundings.
Planning, interfaces, and quality assurance
Careful planning considers geology, groundwater, the position of existing utilities, and shaft logistics. For deconstruction or repair, access points, separation joints, and lifting points are defined in advance. Measurements and tests (e.g., leakage tests, geometry surveys) accompany the process to verify target values. The choice of method is always adapted to the structure, boundary conditions, and the required level of minimal intervention.
Relation to tools and application areas of Darda GmbH
The link between thrust pipes and the tools of Darda GmbH arises from practical demands in tight, sensitive working environments:
- Concrete demolition and special deconstruction: precise removal on reinforced-concrete thrust pipes, opening socket areas, removing damaged segments with concrete demolition shears; cutting reinforcement with combination shears or steel shears.
- Strip-out and cutting: creating inspection openings and recesses in the pipe shell; a combination of splitting and shear work reduces vibrations and enables clean edges.
- Rock excavation and tunneling: use of rock and concrete splitters to loosen surrounding rock during exposure or to relieve jammed pipe joints; power supply via suitable hydraulic power packs.
- Special operations: situations with restricted access, night work in urban settings, or work near sensitive infrastructure where low-vibration, controlled separation and splitting methods are required.