10
SEP 26
Marine
Structural Relining of Pressurised Injection Bore Casings
Tunnel Vision was engaged by a major Western Australian mining operator to develop and implement a trenchless repair solution for leaking joints within PVC injection bore casings at a remote Pilbara mining operation.
Unlike a conventional drainage or pipeline rehabilitation project, the affected assets were vertical injection bores operating under pressure, with repair locations several metres below ground level. Excavation or replacement of the bore casing would have been highly disruptive and impractical, so the client approached Tunnel Vision to determine whether structural cured-in-place pipe (CIPP) technology could be adapted to repair the damaged sections internally.
What began as the repair of a single bore developed into a multi-stage rehabilitation program, with Tunnel Vision subsequently returning to repair additional injection bores across the site’s borefield.
The Challenge
The original asset consisted of approximately 300mm nominal diameter threaded PVC bore casing with an internal diameter of approximately 270–271mm.
Leaks had developed at threaded casing joints within the bore, including joints approximately 3.5m and 9.5m below ground level. The bore operated at approximately 350kPa, creating an unusual environment for a sectional CIPP installation.
The project presented several technical and operational challenges:
Positioning
Repair locations were positioned deep within vertical bore casings rather than conventional horizontal pipework.
Diameter Requirements
The internal diameter needed to remain sufficient for the client’s injection equipment to pass through the repaired sections.
Interference Reduction
Liner transitions had to avoid creating sharp edges that could interfere with installation or removal of bore equipment.
Accounting for Process
Installation pressure needed to account for the increasing pressure experienced as the liner installation depth increased.
Operational Coordination
The borefield was operational, requiring repairs to be carefully coordinated around depressurisation and removal of injection equipment.
Mobilisation
The works were undertaken at a remote mine and borefield location, requiring mobilisation of technicians, specialist equipment, materials and mine-compliant vehicles.
Location
Later stages involved multiple bores located across a remote borefield, with approximately one kilometre between individual assets.
The first installation also provided valuable site-specific information. During installation, Tunnel Vision identified that bladder inflation pressure needed to be adjusted considerably as installation depth increased. This knowledge was incorporated into subsequent bore repairs and installation planning.
Developing the Solution
Tunnel Vision proposed a targeted structural CIPP relining solution that allowed individual defective casing joints to be repaired internally without excavation or replacement of the complete bore casing.
The existing bore casing was inspected and accurately measured before each installation. The repair areas were mechanically prepared to provide an appropriate surface for the structural liner, with CCTV inspections used throughout the process to verify the condition of the asset and completed installation.
Custom composite liners were prepared to suit the approximately 271mm internal diameter of the bore casing and positioned at the nominated depths using specialist sectional relining equipment.
Once positioned, the liner was expanded against the existing PVC casing and allowed to cure in place, creating a new structural section across the defective joint.
Following curing, the installation bladder was removed and the repaired section was inspected before the asset was handed back for recommissioning.
From Trial Repair to Repeat Application
The first bore repair was undertaken in August 2022 and presented several installation challenges associated with accurately positioning liners deep within the vertical bore. Tunnel Vision’s technicians adapted the installation methodology on site, including modifying inflation requirements and installation techniques to suit the increased depth.
Following completion, the mining client confirmed that the repaired bore was holding and had been returned to service.
The successful outcome resulted in Tunnel Vision being asked to undertake a similar repair on another injection bore, where two defective casing joints were located at approximately 6m and 12m below ground level.
For the second bore, the casing was depressurised and dismantled to provide access before the pipe was mechanically prepared. A 1.5m x 271mm composite liner was installed, cured and inspected, followed by installation of the second structural repair.
Four-Bore Rehabilitation Program
Following the earlier repairs, Tunnel Vision was engaged to rehabilitate a further four injection bores within a remote borefield. Downhole CCTV inspections identified defective joints at varying depths, including repair locations between approximately 1.7m and 10.8m below ground level.
The project required multiple structural repairs across four separate 270mm internal diameter bore casings. Because the borefield remained operational, the mining operator coordinated removal of injection units individually to minimise disruption and injection downtime.
Tunnel Vision planned the works as a five-day site program, with approximately 48 hours allowed following curing before individual bores were returned to operation.
During the June 2024 mobilisation, the Tunnel Vision team progressively moved between the bore locations, preparing each casing and installing structural composite liners at the nominated depths. Individual repairs included 1.5m x 271mm liners installed at depths exceeding 11m.
The works incorporated:
- Mobilisation of specialist relining equipment to the remote mine site.
- Site induction, pre-start and safe work requirements.
- CCTV inspection and measurement.
- Mechanical preparation of the PVC casing.
- Preparation of custom composite liners and installation bladders;
- Sectional CIPP liner installation at predetermined depths.
- Controlled curing.
- Removal of installation bladders.
- Post-installation CCTV inspection.
- Progressive relocation between bore assets to minimise overall project duration.
The Result
Tunnel Vision demonstrated that structural CIPP relining could be successfully adapted to a highly specialised mining application involving vertical, pressurised PVC injection bore casings.
The initial repair avoided replacement of the bore casing and allowed the asset to be returned to service. Its performance subsequently led the client to engage Tunnel Vision for additional bore repairs and ultimately a larger multi-bore rehabilitation program.
The project provided the mining operator with a targeted trenchless rehabilitation method capable of repairing isolated casing defects deep below ground while avoiding extensive excavation and complete bore replacement.
For Tunnel Vision, the project also demonstrated the adaptability of structural pipe relining beyond conventional sewer and stormwater infrastructure, applying proven CIPP principles to a highly specialised mining asset in a remote and operationally demanding environment.
Scope of Works
- Assessment of leaking and defective PVC injection bore casing joints
- Remote mine and borefield mobilisation
- CCTV inspection and dimensional verification
- Mechanical preparation of existing PVC casing
- Custom structural composite CIPP liner preparation
- Sectional liner installation in approximately 270–271mm ID bore casing
- Repairs installed at depths exceeding 11m below ground level
- Controlled liner inflation and curing
- Post-installation CCTV verification
- Coordination with mine operations to minimise borefield downtime
- Multi-stage rehabilitation across several injection bore assets
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10
SEP 26
Construction
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