Skokie, Illinois USA
This project involved a 75 year old sewer tunnel 8,800 feet
(268m) long located in Skokie, Illinois. The 78" diameter horsehoe-shaped
tunnel was in need of rehabilitation. Initial planning involved
relining the tunnel with six inches of rebar-reinforced concrete
with an epoxy coating. To meet deadlines, the selected contractor
(Kiewit/Powers joint venture) had begun fabricating steel arch
forms to be used in relining the tunnel.
Because the tunnel was in use and carrying a 2/3 capacity normal
flow, it could not be inspected prior to the initial planning
stages. Prior to the start of the project, a videotape of the
tunnel was made by floating a video camera and flood lights
through the tunnel on a pontoon raft. Upon inspection, it was
realized that only a short segment of the aging tunnel was straight
enough to reline using the methods originally planned.
It was determined that the relining would require a wet mix
shotcrete application with rebar reinforcement (using a remotely
operated arm and nozzle assembly) followed by a hand-trowel
finish that would act as a base for the final epoxy coating.
The wet mix shotcrete specification called for 6,000 psi concrete.
The first layer would be 5 to 6 inches thick, with alkali-free
accelerator added at the nozzle for better adhesion and faster
set. The second coat would be applied without accelerator and
finished with hand trowels so that the epoxy could be applied
Shotcrete Technologies' Shot-Tech Robotic Arm and Shot-Tech
Nozzle assembly were selected because of their demonstrated
ability to apply high-quality, high-production consistent shotcrete.
The safe operation of the robot in the small tunnel was also
of great importance to the Kiewit/Powers personnel.
The South Leg Tunnel project confirmed a number of Shotcrete
Technologies' capabilities that solve tough shotcreting problems:
the Shot-Tech Robotic Arm, wet mix shotcrete can be accurately
and consistently placed in a small, confined tunnel or other
similar enclosed space.
mixed shotcrete can also be used to finish large areas. Kiewit/Powers
realized daily production progress of 120 to 150 linear feet
mix shotcrete can be easily pumped through a small diameter
line from a source hundreds of feet from the robot.
To receive a copy of a videotape of the South Leg Tunnel shotcreting
process, please please call Shotcrete Technologies at (303)
567-4871 or send an e-mail request to email@example.com.