3
Box 30645, Lansing, Michigan 48909-8145, 24 hours before allowing employees to enter the
tunnel.
(4) If the work operations of any occupied and pressurized tunnel projects are discontinued
for 30 consecutive days or longer, then the employer shall notify the Construction Safety and
Health Division at the Michigan Department of Licensing and Regulatory Affairs, 24 hours
before resuming work operations on the tunnel project.
R 408.41471 Ground support; inspections; repairs.
Rule 1471. (1) A qualified employee shall inspect the roof, face, and walls of portals, work
areas, and haulage ways, or travel-ways at the start of each shift and frequently thereafter as
needed. If loose soil or rock or fractured material is encountered, then it shall be scaled or
protected and supported. The employee conducting the inspections shall be protected from
loose ground by location, ground support, or equivalent means. Suitable protection shall be
provided for employees exposed to the hazard of loose ground while installing ground
support systems. Support sets shall be installed so that the bottoms have sufficient anchorage
to prevent ground pressures from dislodging the support base of the sets. Lateral bracing
(collar bracing, tie rods, or spreaders) shall be provided between immediately adjacent sets to
ensure added stability. Damaged or dislodged ground supports that create a hazardous
condition shall be promptly repaired or replaced. When replacing supports, the new supports
shall be installed before the damaged supports are removed. A shield or other type of support
shall be used to maintain a safe travel way for employees working in dead-end areas ahead of
any support replacement operation.
(2) A scaling bar shall be in good condition. A blunted or severely worn bar shall not be
used.
(3) A torque meter and a torque wrench shall be available where rock bolts are used for
ground support. Frequent tests shall be made to determine if the bolts are tight. The test
frequency shall be determined by rock conditions and distance from vibration sources.
(4) A damaged or dislodged tunnel support shall be repaired or replaced when structural
integrity is impaired. A new support shall be installed if possible before removing damaged
supports.
(5) Tunnel supports shall be designed and installed to prevent pressure from pushing them
inward into the excavation.
(6) Roof supports shall be used where ground conditions are such that there could be a
ground failure ahead of tunnel sets.
(7) A tunnel that is to be occupied by employees shall be provided with a steel casing,
concrete pipe, timber, or other material of required strength to support the surrounding earth.
(8) If an employee is required to enter a tunnel or an auger boring and jacking operation less
than 3 feet in diameter, then a lifeline for instant rescue shall be securely fastened to his or
her ankles. Another employee shall be stationed at the tunnel entrance to operate the lifeline.
In addition, ventilation shall be provided with an air line.