Pipe Jacking (TBM) Trenchless Installations
Pipe Jacking (TBM) Trenchless Installations are sophisticated methods used for installing underground pipelines and conduits with minimal surface disruption. This technique employs hydraulic jacks to push specially designed pipe behind Tunnel Boring Machines (TBMs) to excavate soil and create tunnels for the installation of new pipes or conduits.
How It Works
Pipe jacking (TBM) is a trenchless installation method that pushes prefabricated pipe into the ground from a launch shaft while a tunnel boring machine (TBM) excavates ahead of the pipe. The TBM – ranging from open-face excavation shields to closed-face wheel machines and earth pressure balance (EPB) machines – is actively steered to maintain precise line and grade. The finished product is a structurally robust pipeline installed with minimal surface disruption, suitable for deep, long, and high-consequence crossings in urban or environmentally sensitive areas.
Benefits
- Structural Final Product
- The installed pipe is the permanent structure—high stiffness, good load capacity, and durable joints.
- Precision on Line and Grade
- Laser/gyro guidance and TBM steering maintain tight tolerances necessary for gravity systems and complex alignments.
- Long Drives & Large Diameters
- Intermittent Jacking System’s (IJS) and face-support TBM’s (EPB/slurry), the method supports significant distances and large bore sizes.
- Minimal Surface Disruption
- Activity is localized at shafts; roads, rail lines, and communities remain open and functional.
- Groundwater & Geology Flexibility
- Pressurized TBMs and annulus grouting manage inflows, reduce over-excavation, and control settlement.
- Worker Safety
- Operations from the surface reduce exposure to confined space conditions; modern systems include continuous monitoring.
Applications & Technical Details
Pipe jacking (TBM) is selected when projects demand precise alignment, robust structural pipe, and minimal surface impact.
- Gravity Sewers & Storm Drains
- Excellent for tight grade control over long distances at depth.
- Typical drive lengths: 300–1,500 feet per drive; longer drives achievable with IJS (site-specific).
- Pipe types: Reinforced Concrete Pipe (RCP) and Glass-Reinforced Polymer (GRP) jacking pipe are common for rigidity, joint integrity, and strength.
- Diameters: Frequently 24–144 inches, with larger possible depending on TBM and pipe design.
- Water & Pressure Mains
- Ideal where continuous casing and protection are required or where open-cut is infeasible.
- Typical drive lengths: 300–1,200 feet; longer with IJS and favorable ground conditions.
- Pipe types: Steel casing or ductile iron; HDPE/PVC often used as carrier pipes inside a steel or RCP casing for corrosion resistance and hydraulics.
- Critical Crossings (Highways, Rail, Airports, Waterways)
- Allows installation without shutting down or excavating through sensitive corridors.
- Pipe types: Steel casing for added structural protection; RCP/GRP where gravity service and long-term stiffness are priorities.
- Diameters & lengths: Tailored to clearance needs—commonly 36–120+ inches and 600–1,500 feet per drive.
- Deep Urban Utility Corridors
- Reduces risks to adjacent foundations and utilities with controlled face support and real-time monitoring.
- Pipe types: RCP/GRP for gravity systems; steel/ductile iron for pressure applications.
- Drive planning: Incorporates lubrication strategy, IJS spacing, and settlement control to maintain performance in complex soils.
- Additional Technical Considerations
- Pipe Design & Joints: Jacking pipes feature short lengths, robust bells/spigots, and compressible joint gaskets to transmit thrust and maintain watertightness.
- Annulus Control: A designed overcut plus lubrication/grout backfill controls friction and limits settlement.
- Instrumentation & Monitoring: Track jacking loads, advance rates, guidance data, face pressures, and surface settlement to validate assumptions and adapt in real time.
- Construction Sequencing: Plan IJS spacing, lubrication injection points, and TBM maintenance intervals to match geology and drive length.
- QA/QC & Testing: Pre- and post-construction surveys, CCTV or mandrel checks (as applicable), and pressure/leak testing for pressure mains ensure performance.
