Tunnel Boring Machine (TBM) Operations SWMS

Tunnel boring machine (TBM) operations excavate a tunnel using a large, complex machine that bores the full face continuously, installs the tunnel lining, and removes the spoil, advancing the tunnel as a sequence of mechanised cycles. A TBM removes much of the manual exposure at the face, but it introduces its own hazards: the powerful rotating cutterhead and the machinery of the TBM, work in the confined and restricted environment of the machine and the tunnel behind it, the management of face pressure in soft-ground or pressurised TBMs to prevent collapse or inrush, interventions into the cutterhead chamber which can be a hazardous-atmosphere confined space, respirable crystalline silica and dust, and diesel or other plant in the tunnel. This document is written on the basis that the TBM is operated to its design and procedures by competent crews, with cutterhead interventions, face pressure and the confined environment rigorously controlled.

TBM operations engage several high risk construction work categories under the model Work Health and Safety Regulations — work involving a tunnel, work in or near a confined space including cutterhead interventions, work in a contaminated or flammable atmosphere, and movement of powered mobile plant — so a safe work method statement is required before the work commences, kept readily accessible, and given to the principal contractor if one is appointed. Where the ground is silica-bearing, excavating and handling it is high-risk processing of a crystalline silica substance, and diesel particulate from tunnel plant is controlled against its standard. This document coordinates the machine-safety, cutterhead-intervention, face-pressure, atmosphere, silica and ventilation controls so the TBM advances the tunnel safely.

Hazards identified

9 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Engineering: operate the TBM to its design and operating procedures, with guarding and interlocks on the cutterhead and machinery, and an energy-isolation regime for maintenance and interventions.
2. 2Engineering: manage face pressure in soft-ground and pressurised TBMs to support the face and prevent collapse, settlement and inrush, with monitoring of face pressure and ground response.
3. 3Administrative: a controlled cutterhead-intervention procedure treating the chamber as a confined space — atmospheric testing, ventilation or compressed-air intervention controls, entry permit, standby and rescue — with the intervention method matched to the ground and atmosphere.
4. 4Engineering: forced underground ventilation designed to dilute and remove respirable crystalline silica, diesel particulate, dust and other contaminants and maintain a safe atmosphere, with continuous atmospheric monitoring.
5. 5Engineering: control respirable crystalline silica at the source — wet drilling and cutting, water suppression and dust capture — supported by ventilation, to keep airborne silica below the exposure standard, monitored against the respirable crystalline silica workplace exposure standard of 0.05 mg/m3 (eight-hour TWA), reframed as a workplace exposure limit from 1 December 2026.
6. 6Engineering: low-emission or filtered underground plant and ventilation to control diesel particulate matter, monitored against the diesel particulate matter exposure standard, currently 0.1 mg/m3 (eight-hour TWA, sub-micron elemental carbon), with a Workplace Exposure Limit of 0.01 mg/m3 (respirable elemental carbon) from 1 December 2026.
7. 7Engineering: plant-and-pedestrian separation in the headings — exclusion zones, positive communication and proximity detection where fitted — and controlled traffic in the restricted space.
8. 8Administrative: prepare a SWMS before the work for the tunnel and confined space high risk construction work, apply the confined space entry and atmospheric controls and permits, and where the work is high-risk processing of a crystalline silica substance, a silica risk control plan with air and health monitoring.
9. 9Administrative: air monitoring for respirable crystalline silica against the respirable crystalline silica workplace exposure standard of 0.05 mg/m3 (eight-hour TWA), reframed as a workplace exposure limit from 1 December 2026, and for diesel particulate, dust and gases, with health monitoring for workers carrying out high-risk silica work and records retained.
10. 10Administrative: a documented underground emergency response and rescue capability — refuge, self-rescuers where required, communication and rescue arrangements — briefed to all workers.
11. 11Administrative: all workers must hold a valid White Card (General Construction Induction Training, CPCCWHS1001) before entering any construction workplace, with underground, confined space and tunnelling competencies verified as applicable.
12. 12Administrative: conduct a pre-shift toolbox talk covering the day's work, ground and atmospheric conditions, the controls, plant movements, required PPE and emergency and rescue procedures, and record attendance in the consultation section.
13. 13Administrative: consult workers and health and safety representatives on the work and its risks, record the consultation, and keep this document available at the workplace.
14. 14PPE: underground high-visibility clothing, head protection, eye protection to AS/NZS 1337.1, hearing protection matched to the measured noise, gloves, and Class I or Class II safety footwear with protective toecap to AS/NZS 2210.3.
15. 15Administrative: review and update this SWMS whenever the work, the ground or atmospheric conditions, the plant or the controls change, after any incident or near miss, when a worker or health and safety representative raises a concern, or at minimum every 12 months.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

A tunnelling project is excavating a tunnel with a tunnel boring machine, boring the face continuously, installing the lining and removing the spoil. Because the work involves a tunnel, confined spaces including the cutterhead chamber, a potentially contaminated atmosphere, and mobile plant, a SWMS is prepared. The TBM is operated to its design and procedures, with guarding and interlocks on the cutterhead and an energy-isolation regime for maintenance. In the soft-ground sections the face pressure is managed to support the face and prevent collapse, settlement and inrush, with face pressure and ground response monitored. When a cutterhead intervention is required, the chamber is treated as a confined space with atmospheric testing, the appropriate ventilation or compressed-air intervention controls, an entry permit, standby and rescue, and the method matched to the ground and atmosphere. Forced ventilation dilutes and removes silica, diesel particulate and gases with monitoring, wet excavation and dust capture control the respirable silica, and the diesel plant is low-emission. Air monitoring tracks silica and diesel particulate, with health monitoring for silica-exposed workers, and an emergency and rescue capability is in place. The SWMS, intervention and monitoring records are retained.

Related legislation

• Model Work Health and Safety Act — primary duty of care; the duty to consult workers; the reckless-conduct offence; and notifiable-incident provisions, as enacted in each jurisdiction.
• Model Work Health and Safety Regulations — Section 291 high risk construction work and the SWMS preparation and review duties, the confined space provisions, and where relevant the crystalline silica high-risk processing, silica risk control plan, air monitoring and health monitoring provisions, as enacted in each jurisdiction.
• Model Codes of Practice — Tunnelling work; Excavation work; Confined spaces; and Managing risks of respirable crystalline silica in the workplace (2025).
• Where blasting is used, the explosives legislation governs the licensing and authorisation of shotfirers and the storage, transport and security of explosives; and the diesel particulate matter exposure standard, currently 0.1 mg/m3 (sub-micron elemental carbon) with a Workplace Exposure Limit of 0.01 mg/m3 (respirable elemental carbon) from 1 December 2026, applies underground.
• Victoria operates under the Occupational Health and Safety Act 2004 and the Occupational Health and Safety Regulations 2017, with the high risk construction work, tunnelling and confined space provisions applying in place of the model instruments.

Frequently asked questions