Tunnel Boring Machine (TBM) Transport

TBM Component Transport Services

Tunnel boring machines are among the most complex pieces of heavy equipment in the world. A full-face TBM for a major transit or water conveyance project can be 50 to 60 feet in diameter — larger than a five-story building in cross-section — and weigh 2,000 to 6,000 tons when fully assembled underground. Because no TBM can be moved intact on a public highway, every deployment involves disassembly into hundreds of individual components at the factory or previous project site, transport by highway, and reassembly at the launch shaft of the new project.

R&RM LLC has been transporting oversize loads and industrial equipment across all 48 continental states since 2011. This page covers TBM component types, the trailer configurations and permit requirements they involve, and the logistical considerations that make TBM transport one of the most demanding segments of the heavy haul industry.

TBM Components We Transport

Cutterhead Sections

The cutterhead is the rotating front face of the TBM — the component that breaks rock or excavates soil as the machine advances. Cutterheads for large-diameter TBMs are fabricated as multiple sections that are bolted together at the jobsite. Individual cutterhead sections vary widely by machine diameter:

• Small-diameter TBMs (10–20 ft diameter): Cutterhead sections for utility tunneling and micro-tunneling machines range from 5,000 to 40,000 pounds per section. These typically transport on a flatbed or RGN lowboy, often within standard oversize permit limits for width and height.
• Mid-range TBMs (20–35 ft diameter): Water conveyance tunnels, highway tunnels, and rail tunnels in this diameter range use cutterhead segments weighing 50,000 to 200,000 pounds each. Each section requires a heavy-duty multi-axle lowboy or hydraulic platform trailer, plus oversize and overweight permits.
• Large transit and water tunnel TBMs (35–60 ft diameter): Major urban transit tunnel machines — such as those used for the Metro systems in Seattle, Los Angeles, and New York — and large water supply tunnels use the largest TBM cutterheads. Individual cutterhead segments for these machines can exceed 200,000 pounds and measure 15 to 25 feet in cross-section, requiring superload permits and hydraulic platform trailer configurations with 20 or more axles.

Main Bearing and Drive System

The main bearing is the critical rotating interface between the fixed shield and the rotating cutterhead. It is a precision-engineered ring assembly — typically 10 to 25 feet in outside diameter and weighing 50,000 to 300,000 pounds for large machines. The main bearing is one of the most sensitive components of the entire TBM — it is a precision machine element with close-tolerance surfaces and internal roller or ball elements. Transport requirements include:

• Custom transport frame designed and approved by the bearing manufacturer to distribute load evenly around the bearing race without concentrating stress on any single point.
• Climate-controlled or covered trailer in some cases for bearings with factory-applied corrosion protection that must not be disturbed before commissioning.
• Shock and vibration monitoring in transit for the most sensitive large-diameter bearings, particularly for new builds where the bearing has not yet been run-in.
• Multi-axle lowboy or hydraulic platform trailer with sufficient axle count to keep axle loads within permit limits given the bearing's weight and transport frame dimensions.

The drive motors, gearboxes, and electric motor assemblies that power the cutterhead rotation ship as separate loads on RGN or flatbed trailers, individually exceeding standard legal weight in many configurations — requiring overweight permits even for individual motor assemblies on large machines.

Shield Sections

The shield is the cylindrical steel body of the TBM — the portion behind the cutterhead that provides structural support to the tunnel excavation and protects the machine's interior from ground pressure. Shields are fabricated as bolted ring sections, typically 8 to 12 sections per ring for large machines. Shield sections for large-diameter TBMs are among the widest and heaviest individual components in a TBM move:

• A shield section for a 40-foot diameter TBM may be 12 to 15 feet wide, 12 to 15 feet tall, and 10 to 20 feet long (depending on how many rings the section spans), weighing 80,000 to 250,000 pounds. These loads require superload permits for width, height, and weight, and in most states require route surveys, utility clearance coordination, and law enforcement escort.
• Shield tail sections — the rear of the shield where completed tunnel lining segments exit the machine — also carry the tail seal brushes and grouting ports. These sections are particularly fragile due to the precision seal geometry and must be transported with custom blocking to prevent distortion.
• The shield for a soft-ground TBM (EPB or slurry face) is more complex than a hard rock TBM shield because it incorporates the screw conveyor or slurry bulkhead, adding both weight and dimensional constraints to individual sections.

Erector and Segment Handling Systems

The segment erector is a large ring-shaped robotic arm inside the TBM that places precast concrete tunnel lining segments into position as the machine advances. For large-diameter TBMs, the erector is a substantial fabricated steel structure — typically 15 to 25 feet in diameter and weighing 50,000 to 150,000 pounds — that ships as a single unit or in two to four major sections. The erector's ring-shaped geometry makes it a dimensional challenge on the highway: its outside diameter often exceeds 14 feet in every orientation, making overheight and overwidth permits unavoidable regardless of how the load is oriented on the trailer.

Segment feeder systems — the conveyor and storage systems that deliver precast segments from the trailing backup to the erector — are long, narrow fabricated structures that ship as multiple loads, each typically 60 to 150 feet long when fully assembled and requiring overlength permits or disassembly into sections for transport.

Backup Trailers and Gantries

Every TBM operates with a train of trailing backup equipment — gantries and trailers that follow behind the machine inside the completed portion of the tunnel, carrying the electrical switchgear, hydraulic power units, slurry or muck handling systems, ventilation equipment, and personnel access. Backup gantry structures ship as large, long steel fabrications — individual gantry frames up to 30 feet wide, 20 feet tall, and 50 to 80 feet long in some configurations. Hydraulic power units for large TBMs are very heavy packaged units — 40,000 to 120,000 pounds — on skid frames that require lowboy transport. Electrical transformer and switchgear modules for large TBMs may each weigh 20,000 to 80,000 pounds, shipping on flatbeds with overweight permits.

Thrust Ring and Jack Systems

TBMs advance using hydraulic thrust cylinders pushing against the last installed ring of tunnel lining. The thrust ring assembly — the structural ring to which the thrust cylinders are attached — is a large circular fabricated steel structure, similar in transport geometry to the segment erector. For large machines, the thrust ring may be 15 to 30 feet in outside diameter and weigh 60,000 to 200,000 pounds, requiring superload-class permits for width and weight. Individual thrust cylinders for large TBMs are heavy hydraulic actuators — up to 30 feet long and weighing 5,000 to 20,000 pounds each — that ship separately on flatbeds.

TBM Manufacturers and Project Types

Herrenknecht AG

Herrenknecht is the world's largest TBM manufacturer, producing machines for every tunneling application — hard rock, soft ground (EPB and slurry face), mixed-face, and micro-tunneling. Herrenknecht TBMs have been used on major US projects including the Alaskan Way Viaduct replacement tunnel in Seattle (57.5-foot diameter Bertha), the East Side Access project in New York, and numerous water conveyance tunnels across the country.

Robbins Company

The Robbins Company, headquartered in Solon, Ohio, is one of the original American TBM manufacturers — producing hard rock TBMs, EPB machines, and continuous miners since the 1950s. Robbins machines have been used on water supply tunnels, sewer tunnels, and mining development drifts throughout the United States. Robbins components typically ship from their Ohio manufacturing facility to project sites nationwide.

Hitachi Zosen (Hizo)

Hitachi Zosen produces shield TBMs primarily for soft-ground applications, with machines widely deployed in transit tunnel projects across North America. Hizo machines have been used on light rail, heavy rail, and road tunnel projects in several US cities.

Caterpillar (formerly NEU / Lovat)

Caterpillar's tunnel boring machine product line — developed through the acquisition of RESA (formerly Lovat) — produces EPB and slurry face TBMs for transit and infrastructure tunneling. Caterpillar equipment components from these tunnel machine product lines require the same oversize transport approach as other TBM brands.

Komatsu (NHI and JIMT)

Komatsu's tunnel machinery division produces TBMs for mining, transit, and water infrastructure projects. Komatsu TBM components follow the same transport logistics framework as other large-diameter machine brands.

Trailer Configurations for TBM Components

Hydraulic Platform Trailers (Modular Platform)

Hydraulic modular platform trailers — multi-axle trailers with independently steerable, hydraulically interconnected axle groups — are the standard equipment for the largest TBM components. A typical configuration for a large cutterhead section or shield segment uses 8 to 24 axle lines (16 to 48 individual axles) in a two-file arrangement, providing the load distribution needed to keep per-axle loads within superload permit limits while maintaining the flexibility to navigate curves and ramps. These trailers operate at 5 to 15 mph under load and require pre-arranged police escorts, utility line raises, and in some cases temporary bridge weight waivers for specific crossings on the delivery route.

Multi-Axle Lowboy Trailers

For components in the 80,000 to 200,000-pound range — main bearing assemblies, smaller shield sections, erector components — multi-axle lowboy trailers with 5 to 8 axle groups provide the necessary weight distribution. These trailers are lower to the ground than hydraulic platform configurations, which can be advantageous for tall components that would otherwise require an overheight permit on a platform trailer. Multi-axle lowboy configurations still require oversize and overweight permits for the largest TBM components in this weight range.

RGN Lowboy Trailers

RGN (removable gooseneck) trailers are used for TBM drive motors, gearboxes, and mid-size fabricated components that require the detachable neck for loading by crane or ground-level access. RGN trailers are standard equipment for components in the 40,000 to 100,000-pound range that exceed flatbed height limits but do not require the full multi-axle platform trailer approach.

Flatbed Trailers

Standard flatbed trailers handle TBM backup system components — electrical panels, hydraulic power pack components, conveyor sections, and smaller structural elements. For backup trailer frames and gantry sections that are long but not excessively heavy, flatbed trailers with overlength permits (for loads extending beyond 53 feet) are the most cost-effective option.

Permit Requirements for TBM Moves

Superload Permits

The majority of large TBM components — cutterhead sections, shield segments, main bearings, erectors, and thrust rings — require superload permits. Superload thresholds vary by state but typically begin at loads exceeding 16 feet in width, 15 feet in height, or 200,000 pounds gross vehicle weight. Superload permit processing involves route survey approval by the state DOT engineering review, bridge load posting analysis for each structure on the route, and in many states a mandatory pre-move utility clearance request. Processing times for superload permits range from one week to four weeks depending on the state and the load dimensions — early permit application is essential for TBM project schedules.

Multi-State Permit Coordination

TBM components moving from factory to project site frequently cross multiple state lines — from manufacturers in Ohio, California, or the Pacific Northwest to project sites in Texas, Florida, or the Northeast. Multi-state permit coordination for superload TBM moves involves simultaneous permit applications in every state on the route, with each state processing its own route review and establishing its own conditions (travel time windows, escort requirements, speed limits). We coordinate permit applications across all states on the route to ensure that permit validity windows and travel conditions are compatible, so that a permit condition in one state does not force the load to violate conditions in another.

Route Surveys and Utility Coordination

For superload TBM components — particularly wide shield segments and large-diameter cutterheads — a physical route survey is conducted before permitting is finalized. The survey identifies overhead obstacles (utility lines, traffic signal structures, bridge clearances) along the entire delivery route. Utility companies are then notified and asked to temporarily raise or reroute lines that fall within the clearance envelope of the moving load. This coordination process can add one to three weeks to the delivery timeline for very wide loads and must be accounted for in the project schedule.

Industries and Project Types Generating TBM Moves

• Transit tunnel projects: Urban light rail, heavy rail, and subway extensions are among the most frequent TBM projects in the United States. Major metro areas — New York, Los Angeles, Seattle, San Francisco, Washington DC, Houston, and Dallas — all have active or planned transit tunneling projects that generate TBM transport demand. See our coverage of New York, California, and Texas heavy haul services.
• Water supply and conveyance tunnels: Large-diameter water supply tunnels for municipal water systems, including aqueducts, transmission mains, and reservoir connections, use TBMs to bore through rock and soil. These projects are concentrated in the Mountain West, Northeast, and rapidly growing Sun Belt metros.
• Highway and railroad tunnels: Mountain highway tunnels and railroad tunnels in the Rocky Mountain region, Appalachians, and Cascades require TBM or drill-and-blast excavation. TBMs are increasingly used where alignment geometry and geologic conditions permit.
• Combined sewer overflow (CSO) tunnels: Cities including Chicago, Indianapolis, Atlanta, Washington DC, and Cincinnati have built or are building large deep rock storage tunnels to capture combined sewer overflows — one of the most active sectors for large-diameter TBM work in the US. These projects often require the largest diameter machines and generate the most demanding TBM transport jobs.
• Mining development tunnels: Underground mining operations use smaller (10–20 ft diameter) hard rock TBMs for development headings in gold, silver, copper, and potash mines, particularly in Nevada, Idaho, and the Mountain West.
• Power and utility tunnels: Hydroelectric projects, pumped storage facilities, and large utility tunnels for power cable and pipeline crossings use TBMs for bore construction. See our guide on heavy haul for the utility and power industry.

Special Handling and Logistics Considerations

TBM transport presents a set of logistical challenges that set it apart from most other heavy haul operations:

• Project schedule sensitivity: TBM deployment is always on the critical path of a tunnel project schedule. Delays in component delivery directly delay the TBM launch date, which delays project completion and can trigger contract penalties. We track permit processing status daily and alert project managers immediately to any delay that threatens the delivery schedule.
• Component sequencing: TBMs are assembled from the front back — the cutterhead and main bearing are installed first, followed by the shield sections and then the backup systems. Components must arrive at the launch site in assembly order, which requires coordinating the departure sequence from multiple shipping origins (factory, rebuild yard, storage yard) against the assembly sequence at the destination.
• Launch shaft access constraints: TBM components are lowered into the launch shaft by crane, often using a large lattice boom crane or crawler crane positioned over the shaft opening. The delivery route must allow the heaviest components to reach the crane's staging area, which is frequently on an urban construction site with limited access. We survey launch shaft access routes and confirm that the trailer configuration can navigate to the crane lift point.
• Manufactured dimensions vs. drawing dimensions: TBM components are large fabricated weldments that can vary from the engineering drawings by several inches due to weld distortion and fabrication tolerance accumulation. We verify actual dimensions at the shipping origin before applying for permits — a fabricated shield segment that measures 13 feet 8 inches rather than the 13 feet 4 inches on the drawing moves the load into a different permit tier in most states.
• Used and refurbished TBMs: Many tunneling projects use refurbished TBMs — machines rebuilt from a previous project for reuse. Refurbished TBM components are shipped from rebuild facilities or from previous project launch shafts where the machine was recovered at the end of the prior job. Used TBM components may not have current dimensional documentation, requiring field measurement before transport.

Getting a Quote for TBM Component Transport

To provide an accurate quote for TBM component transport, we need the following information for each major component:

• Component type (cutterhead section, shield section, main bearing, erector, backup gantry, etc.)
• TBM manufacturer and machine diameter
• Weight (from the manufacturing drawing or a certified scale ticket)
• Overall transport dimensions: length, width, and height as shipped on the trailer
• Origin location (factory, rebuild yard, previous project site)
• Destination (launch shaft location, project address)
• Required delivery date and assembly sequence requirements
• Loading/unloading equipment available at origin and destination

R&RM LLC handles permit applications, trailer coordination, route surveys, and delivery sequencing for TBM projects. Call us at (404) 987-6225 or use the form below to start your TBM transport quote.