Case Studies

Mainline Segment 9, I-20/ Railroad Crossing – TBM 48SCII, 50-in. OD Disc Cutter Head, Tunnel Boring System with 5200 Pump Unit, 524 Haul Uni

Project Details

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Project Name
Mainline Segment 9, I-20/Railroad Crossing
General Contractor
Culberson Construction, LLC/J & J Boring, Inc
Location
Midland, TX
Ground Conditions
Varying UCS caliche and limestone rock
Akkerman Equipment
TBM 48SCII, 50-in. OD Disc Cutter Head, Tunnel Boring System with 5200 Pump Unit, 524 Haul Unit
Pipe
48-in. OD Steel Casing
Total Length/Hard Rock Section
550-lf./250-lf. (DCH used for 250)

Project Overview

The project involved the construction of a 36-in. diameter HDPE water line inside of a 48-in. diameter casing, that ran under highway I-20 and a Union Pacific Railroad near Stanton, TX.

While using their 48SCII TBM with standard carbide cutter head, J & J Boring, Inc. encountered rock conditions midway across the bore which were not stated in the pre-bid GDR. The unanticipated ground proved challenging to mine with the initial TBM cutter head setup. After a few worn tooling changes, the contractor decided to develop a better solution to mine the rock.

Challenges

  • Installation in hard caliche/limestone rock
  • Crossing under active rail line and I-20 Highway
  • Actual project rock rating was 40% harder than pre-project GDR indicated
  • Hardest rock encountered within sensitive rail road Zone A, requiring 24-hour non-stop construction and no surface access

Solution

Key benefits of owning an Akkerman TBM is the interchangeable cutter heads feature and the ability to access the face for obstruction removal. J & J Boring, Inc. contacted Akkerman for a Disc Cutter Head attachment for their 48SCII TBM to fracture the hard caliche and limestone rock into pieces while maintaining alignment despite geological variations.

The 48SCII TBM Cutter head features:

  • (16) 6.5-in. disc cutters, capable of 5 tons of thrust each
  • Cutter head rock scrapers assist in transferring cuttings away from the face, to the conveyor, then to the haul unit for removal from the tunnel
  • Heavy-duty bearing to handle disc thrust loads
  • Recommended uni-directional operation for effective mining

The lead 48-in. casing was welded to the TBM to counteract the rotational torque necessary to mine the rock with the uni-directional cutter head. The operators monitored the thrust loads on the cutters to ensure they did not become overloaded.

Outcome

  • J & J Boring, Inc. completed the drive in challenging rock that would have been otherwise improbable
  • No cutter head tooling replacements required
  • Mid-project rock testing indicated project rock samples of 13,000 PSI UCS.

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