A shield machine (TBM) installation on a metro or utility-tunnel site runs through five tightly sequenced phases — shaft/lifting preparation, launch-trough build-up, shield tail-null commissioning, segment-handling trial, and main-drive no-load test — each with named acceptance values and per-phase risk gates, per industry practice tracked under [S1].
The procedure is governed by the shield machine category selected for the project (slurry, EPB, composite, or rock TBM), the project's GB 50299-aligned technical specification, and the OEM's site-assembly manual; the order of steps is not interchangeable because later phases inherit geometric tolerances from earlier ones.
Phase 1: Shaft Preparation and Heavy-Lift Rigging
The receiving shaft must be dimensionally verified against the shield OD plus 600–800 mm working clearance before the first crane is mobilised, with the invert level tolerance held to ±10 mm and the shaft wall verticality ≤ 0.1% of shaft depth per typical metro-tunnel handover sheets [S1].
Heavy-lift cranes are rated for the heaviest single-piece lift (cutter head, main drive, or shield body) plus a 1.25× dynamic factor; crawler cranes in the 300–600 t class are common for 6 m-class EPB shields, and dual-crane tailing lifts require a written lift plan with sling-angle calculations kept below 60° to the horizontal [S1].
The shaft base must support the assembled shield's weight distributed over the reaction frame; geotechnical checks for the launch wall and tail seal are non-negotiable, and a clean, dewatered working floor is required before any shield body segment is staged — water ingress above 5 mm/h triggers re-grouting.
Phase 2: Launch-Trough Build-Up and Back-Up Configuration
The launch trough is the steel-reinforced reaction frame that pushes against the segment ring, and its concrete back-wall must achieve the design compressive strength (typically C30–C35) before the first thrust-jack extension, with curing records logged for at least 7 days under standard conditions [S1].
Back-up gantries (trailing cars) are coupled in numbered sequence per the OEM layout, and the umbilical routing for slurry lines, grout lines, ventilation ducts, and HV power cables is verified against the cable-tray GA before the first car is connected — a misrouted umbilical is the single most common cause of restart delays in the first 30 m of mining [S1].
Common installation kits used alongside the launch frame include linear guide rails for the segment feeder and crossed-roller guide bearings for the erector swing ring; preload and lubrication spec sheets must be on site and signed before the erector is energised.
Phase 3: Shield Tail-Null Commissioning and Seal Test
After the shield body is set on the launch cradle, the tail-skin brushes are installed and the grease-fill procedure runs through every row; the test pressure is held at 0.3–0.5 MPa above the expected groundwater head at the tunnel crown, and any pressure drop exceeding 5% over 30 minutes fails the test [S1].
The shield tail null (gap) is measured at 12 clock positions around the ring; the standard tolerance band is 0–30 mm with a maximum delta of ≤ 10 mm between adjacent positions, otherwise the tail skin will foul the segment during the first push stroke [S1].
Tail-skin wire brushes must be the same OEM part number as the tail-body spec, and grease types are not interchangeable between manufacturers — substitution is a documented failure mode and is flagged in site NCRs because it voids the waterproofing warranty on the first 100 rings.
Phase 4: Segment-Handling and Erector Trial
The segment feeder and vacuum/erector system are dry-run cycled at least 10 times before the first segment is lifted; each cycle confirms the segment is held within the erector's grip-force window (typically 1.5–2.5× the segment self-weight) and that all limit switches latch in the correct sequence [S1].
Segment stockyard handling is a frequent bottleneck, and the face shield and PPE rules in the cutting-shop area apply to the gantry crew whenever a segment is suspended — a hard barrier with interlocks is required on every back-up car where segments travel overhead.
During the trial, segment ring build-up is recorded in a ring-log book with ring number, segment orientation, bolt torque values (typically 350–500 Nm for M30 segment bolts), and any visual defects; the first 10 rings form the reference baseline used by the survey team to track tail-skin wear for the rest of the drive.
Phase 5: Main-Drive No-Load Test and Cutter-Head Rotation
Before mining starts, the main-drive motors are run uncoupled for at least 2 hours at incremental speeds up to the rated RPM (typically 1.0–3.0 rpm for 6 m EPB), and bearing temperatures must stabilise below 70 °C with no abnormal vibration peaks above 4.5 mm/s RMS [S1].
The cutter-head rotation direction and spoke-opening alignment are verified against the geological profile of the first 20 m of ground; slurry or foam injection lines are flushed and pressure-tested at 1.5× working pressure, and a 10-minute leak-free hold is the pass criterion [S1].
For projects pairing the TBM with coding machine consumables on the segment side or core machine tooling in pre-investigation boreholes, the interface timing must be coordinated so that no coding or coring crew is on the back-up gantry during the no-load test.
Acceptance Criteria, Failure Modes, and When to Stop
The whole five-phase sequence carries a hard stop on any of four conditions: tail-skin seal pressure drop > 5% in 30 min, main-drive bearing temp > 75 °C during the no-load run, back-wall concrete < design strength at the first thrust, or shield null delta > 10 mm between clock positions [S1].
Common NCR triggers that block moving to mining include mismatched tail-skin brushes, undocumented grease substitutions, lift-plan absence for any single piece > 80 t, and missing ring-log entries for the first 3 trial rings — none of these are paper-only issues; each has caused documented first-50-m downtime in metro projects [S1].
Site crews should reference the project-specific coding machine types and classifications for the segment-marking layer, linear bearing installation for the erector swing-ring maintenance baseline, and the dynamic compactor installation spec map for the launch-pit ground-improvement steps.
Trackable signals: (1) signed lift plan + tail-seal test certificate, (2) commissioning report countersigned by OEM site engineer and project QC, and (3) first 10 ring-build logs handed to the survey team before mining starts on ring 11.