513 EM 385-1-1 Chapters 23-29

Sections

26-8. General Requirements.

Access and Egress

The Designated Person must control access to underground openings to prevent unauthorized entry.
Authorized Entrant access must be coordinated and controlled as per OSHA requirements.
Worker documentation procedures and a check-in/check-out system must be established in accordance with 30 CFR 57.11058.

Tunneling in Soil

For conventional excavation methods, do not extend excavation beyond 24 inches ahead of ground supports. For continuous mining machines, the limit is 48 inches.
Under no circumstances should persons work in unsupported sections of tunnels.
All voids behind ground supports must be filled, blocked, braced, or treated to prevent cave-ins.

Shafts

Support all shafts over 5 feet in depth with appropriate materials to prevent earth shifts.
Do not allow entry into unsupported auger-type excavations in unstable material.
Ensure two safe means of access in shafts at all times, such as a ladder and hoist.

Protection from Falling Material

A Competent Person (CP) must inspect the work area at each shift's start and as needed to ensure tunnel stability and protection from falling material.
Secure or remove rock masses separated by discontinuities, as designed by a qualified professional.
Implement protective measures such as anchored chain-link fabric on rock faces prone to spalling, and provide protective shelters at underground portals as necessary.

Knowledge Check Choose the best answer for the question.

26-6. For tunneling using continuous mining machines, the limit for extending excavations ahead of ground supports is _____.

18 inches

24 inches

48 inches

60 inches

You forgot to answer the question!

EM 385-1-1 Paragraph 26-8 (a.–d.).

26-8. General Requirements. (a.–d.).

Paragraph 26-8 applies to the construction of underground tunnels, shafts, chambers, and passageways.  Paragraph 26-8 also applies to cut-and-cover excavations which are both physically connected to ongoing underground construction operations within the scope of this paragraph and covered in such a manner as to create conditions characteristic of underground construction.

a.  Access and Egress.  The Designated Person is responsible for controlling the access to all underground openings to prevent unauthorized entry.  Authorized Entrant access must be coordinated and controlled according to OSHA requirements.  Establish worker documentation procedures and a check-in/check-out system according to 30 CFR 57.11058.  (26-8.a)

b.  Tunneling in Soil.  (26-8.b)

(1)  Where tunnels are excavated by conventional methods, the excavation must not be extended more than 24 inches (61 cm) ahead of ground supports.  Where continuous mining machines are used for tunnel excavation, the excavation must not be extended more than 48 inches (122 cm) ahead of ground supports.

(2)  Do not permit under any circumstances persons to work in unsupported sections of the tunnels.

(3)  All voids behind ground supports must be filled, blocked, braced, or treated to prevent further cave-ins.

(4)  Where liner plate is not used for tunnel support, 2 inches (5.1 cm) wire mesh or chain-link fabric must be installed over the crown section, extending down to the spring line on each side of the tunnel and secured in place.

c.  Shafts. (26-8.c)

(1)  Shaft Support.

(a)  Support all wells or shafts over 5 feet (1.5 m) in depth with lagging, piling, or casing of sufficient strength to withstand shifting of the surrounding earth.

(b)  Support the full depth of the shaft by casing or bracing, except where the shaft penetrates into solid rock having characteristics that will not change because of exposure as determined by a QP.

(2)  Unsupported Auger-Type Excavations.  Do not permit employees to enter an unsupported auger-type excavation in unstable material for any purpose.  In such cases, necessary clean-out must be accomplished without entry.

(3)  Safe Shaft Access.  There must be two safe means of access in shafts at all times. This may include a ladder and hoist.

d.  Protection from Falling Material.  (26-8.d)

(1)  A CP must inspect the roof, face, and walls of the work area at the start of each shift and as often as necessary to determine the stability of the tunnel and adequate protection from falling material.

(2)  Rock masses separated from the main mass by discontinuities must be secured by rock bolting, other suitable means, or must be removed.  A geotechnical engineer, structural engineer or other QP must design the means of securing the rock masses.

(3)  Provide anchored chain-link fabric, or other method approved by the USACE
    supervisor or accepted by the KO or COR, on rock faces subject to spalling.

(4)  Where tunnels are excavated through earth or shale, any excavation above or adjacent to portal areas must be sloped to the angle of repose or held in place by
    ground supports. When undercutting occurs on these slopes, whether due to erosion or other causes, the overhanging material must be promptly removed.

(5)  Provide a protective shelter at each underground portal to protect persons and equipment from the hazards of falling rock or other material, when necessary.  The protective shelter must be made of sufficiently durable and strong material and sized appropriately based on work site conditions and risk.  This determination must be documented in a site-specific APP, or equivalent document.

(6)  Promptly remove ice or snow buildup on rock faces or earth slopes that create a hazard.