Tunnel pipeline

The term tunnel pipeline encompasses lines and line systems that are installed within tunnel structures or routed through tunnel systems—from pressure pipelines for water and district heating to gas and ventilation lines and cable trays for power and communications engineering. In planning, construction, maintenance, and deconstruction, utility line installation, civil engineering (underground works), and tunnel construction intersect. Work on tunnel pipelines often calls for precise, low-vibration, and controllable methods. In such situations, in the context of concrete demolition and special demolition, tools such as concrete demolition shear as well as hydraulic wedge splitter from Darda GmbH are regularly considered, for example when creating breakthroughs, recesses, fixings, or when selectively dismantling components.

Definition: What is meant by tunnel pipeline

A tunnel pipeline refers to any utility line or cable routing that is run within the cross-section of a tunnel or in associated structures (shafts, cross passages, technical rooms). This includes pipelines (e.g., water, wastewater, gas, compressed air, district heating), ventilation and drainage lines, as well as electrical installations and cable trays. Functionally, supports, brackets, anchors, dampers, fire stop assemblies, expansion joints and compensation elements, as well as penetrations through the tunnel shell, are part of the system. The tunnel pipeline is therefore part of the building services equipment and is subject to specific requirements regarding load-bearing capacity, durability, safety, accessibility, and operation.

Structure and components of tunnel pipelines

Tunnel pipelines consist of the actual medium carrier and a variety of supplementary components that enable safe routing and operation.

Types of lines and materials

• Pipelines: steel, stainless steel, ductile iron pipe, HDPE, PP, GRP; depending on medium, temperature, pressure, and corrosion environment.
• Cable trays: cable ladders, riser trays, protective conduits, and microduct systems for power, signal, and communications.
• Ventilation and drainage: ducts, pipes, channels, drip edges, and separators for condensate and water management.

Fixing and supports

• Hangers, brackets, rail and heavy-duty systems with anchor fixings in shotcrete or inner-shell concrete.
• Sliding and fixed points, expansion loops, and compensators to accommodate thermal elongation and dynamic actions.
• Vibration and structure-borne sound dampers to reduce effects from traffic, machinery, and flow.

Penetrations and separations

• Sealing systems against water and gas ingress, coordinated with the structure’s waterproofing and design water pressure.
• Fire stop solutions and separations to limit the spread of fire and smoke.
• Service and inspection openings, access panels, recesses, and shafts for operation and maintenance.

Depending on the construction phase, low-vibration methods are suitable for producing recesses, cable channels, or openings in the tunnel shell. Concrete demolition shear is used for targeted removal of concrete in layer thicknesses, while hydraulic wedge splitter locally builds up stresses in rock or concrete to create controlled cracks. Hydraulic power for this is supplied by Darda GmbH compact hydraulic power units—particularly relevant in confined spaces.

Planning, routing, and structural requirements

The routing of tunnel pipelines is determined by cross-section geometry, accessibility, protection needs, and minimum clearances to traffic and rescue spaces. Static and dynamic loads (self-weight, pressure, temperature, traffic, earthquakes) must be considered, as well as installation and maintenance access.

• Load transfer: design of brackets and anchors under combined loading.
• Thermal and pressure effects: expansion concepts, fixed and sliding bearings, compensators.
• Redundancy and operations: shut-off and drain capabilities, separation points, sectorization for maintenance during ongoing operation.
• Protected spaces: keeping escape routes and refuges clear; cable protection against impact and thermal loads.

When adapting existing structures—for example, to retrofit additional cable trays—precise interventions on concrete or rock surfaces are required. In practice, selective, low-dust, and low-vibration methods are preferred, in which concrete demolition shear removes material step by step and rock wedge splitter exposes local slots or recesses in rock.

Construction methods in tunnel and pipeline works

The implementation of tunnel pipelines follows the tunnel’s construction progress (shotcrete method, shield or TBM excavation, inner-shell concrete) or is carried out in existing assets. Typical sequence:

1. Pre-assembly of support rails and brackets after surveying the route.
2. Lifting in or pulling in the lines, installing fixed and sliding bearings.
3. Producing penetrations and separations, leakage tests, and commissioning.

For new works and retrofits in rock sections or in areas with heavily reinforced components, hydraulic wedge splitter and, additionally, shear tools (e.g., for cutting reinforcing steel with a rebar cutter) are often used for blockouts, widenings, and controlled separation cuts. In segment joint areas, interventions require particular care; low-vibration methods help preserve the integrity of adjacent joints and seals.

Safety, fire protection, and medium-specific aspects

Tunnel pipelines are subject to heightened safety requirements. Depending on the medium, requirements apply to leakage limitation, fire and explosion protection, drainage, and monitoring.

• Fire load management: selection of low-flammability cable trays and fire-rated separations.
• Leakage and pressure monitoring: shut-off and drain valves, containment areas, grading for safe discharge.
• Temperature control: insulation, trace heating, or cooling to stabilize operating temperatures.
• Rescue and operations: keeping minimum cross-sections clear; robust fixings against impact loads and negative/positive pressure events.

When intervening in areas with critical media, low-sparking and low-vibration work is preferred. This includes controlled removal methods with concrete demolition shear and, when rock exposure is necessary, rock wedge splitter. Metallic lines and inserts can—depending on the project—be cut segment by segment using shear tools, without large-area heat input, for example with a steel shear.

Maintenance, condition assessment, and rehabilitation

Long-term operation requires regular inspections and planned renewals. Typical measures:

• Visual and functional checks, tightness or pressure tests, corrosion monitoring.
• Cleaning of drainages, drainage gutters, and filter layers to ensure performance.
• Retightening or renewing anchors, replacing worn bearings and compensators.
• Refurbishment of coatings and wrapping systems; cathodic corrosion protection for metallic pipelines.

In existing structures, precise interventions on concrete, rock, and reinforcement are often necessary. For selective opening and low-deformation removal of components, tools that work material-appropriately are suitable: concrete demolition shear for controlled stepwise concrete removal; hydraulic wedge splitter for crack initiation in brittle materials; shear tools for reinforcement and steel components. This allows routes to be widened, fixings replaced, or penetrations retrofitted without significantly affecting the tunnel shell.

Deconstruction, conversion, and special demolition in tunnels

When tunnel pipelines are decommissioned, converted, or replaced, the focus is on special demolition. The goal is safe, sectional dismantling under restricted space conditions.

• Selective separation of pipeline runs, brackets, and hangers.
• Removal of separations and controlled closing of penetrations.
• Local concrete removal to expose concealed routes or supports.

In special deployments—for example in incidents, after events with thermal impact, or in inaccessible legacy installations—compact hydraulic tools with high power density are required. Concrete demolition shear and hydraulic wedge splitter enable low dust and low vibration levels. For shortening metal components, steel shear or multi cutters may be used depending on material thickness. Darda GmbH hydraulic power pack support operation under tunnel conditions (ventilation, power supply, rescue routes).

Material selection, corrosion protection, and durability

Tunnel environmental conditions—moisture, chlorides, carbon dioxide, splash water, temperature changes—affect material selection and protection concepts.

• Metallic pipelines: material selection among non-alloyed steels, stainless steel grades, or ductile iron pipes; internal and external coatings, linings.
• Plastic and composite systems: HDPE, PP, GRP for corrosive media or low weight; specifics for fixation and thermal expansion.
• Fixings: corrosion-protected anchors and brackets; separation of contact pairs to prevent galvanic corrosion.

During rehabilitation, removing damaged concrete cover and exposing reinforcement is a recurring step. Here, concrete demolition shear, through its layer-by-layer working approach, contributes to controlled component processing; rock wedge splitter helps open brittle zones without thermal influence.

Interfaces with structure, operations, and logistics

Tunnel pipelines interact with traffic space, rescue routes, and operating equipment. Planning and construction take into account installation routes, lifting and conveying logistics, and site organization during ongoing operation.

• Installation within the cross-section: sequencing, prefabrication, minimization of closures.
• Coordination with rail operations or road traffic: protective measures, dust and noise reduction.
• Construction logistics: energy supply for hydraulic power pack, ventilation and dust extraction, safe waste streams.

Confined spaces and low permissible emissions favor compact, hydraulic tools. This includes the use of concrete demolition shear for concrete sections and hydraulic wedge splitter in rock areas.

Sustainability and deconstruction-friendly design

Sustainable tunnel pipelines are designed for longevity, reusability of components, and clean separation by material during deconstruction.

• Modular fixing systems and documented anchor points facilitate conversions.
• Material separation and low-dust dismantling reduce environmental and health impacts.
• Planning of inspection access reduces interventions and extends maintenance intervals.

Methods with low vibration and without thermal influence—including splitting rock or controlled removal of concrete—contribute to a resource-conserving life cycle and support rock excavation and tunnel construction as well as concrete demolition and special demolition.

Practical examples of typical work steps

• Creating a cable recess in shotcrete: removing the surface layer with a concrete demolition shear, targeted widening with a rock wedge splitter, reprofiling, and installation of the bracket.
• Retrofitting a drainage line: opening the tunnel shell in the area of the penetration, installing the separation, installing the line, backfilling, and reprofiling.
• Deconstruction of an obsolete route: sectional release of hangers, shortening metal components with shear tools, closing penetrations no longer required.

Such sequences show how tunnel pipelines can be handled over their entire life cycle—from construction to maintenance to conversion. Tools and methods are always selected to ensure the stability, safety, and operation of the structure.