| Tanana River Bridge #505, Tok,
Alaska
Malcolm Drilling furnished and installed 10’ diameter
permanent steel casing at five (5) shaft locations with
Leffer 3050 oscillator equipment on this project: one
pier location was on land, two were installed on a sand
island constructed in the river, and two were installed
from a work trestle and finger piers constructed over
the river. Permanent steel casing segments were welded
together vertically over the shaft location with the
deepest casing installed at a length of 176’ - the deepest
shaft in Alaska history. A Liebherr 885 dig crane excavated
the shafts utilizing a 3M spherical grab, dumping shaft
sands and gravels into waiting dump trucks. Four of
the shaft locations feature rock sockets up to 39’ deep
below the permanent casing. MDCI placed all reinforcing
steel cages as single units and then furnished and placed
4000P shaft concrete in all shafts.
Malcolm also furnished and installed four (4) 4’ diameter
permanent steel casings at Abutment 1 that were slipped
inside of temporary oscillator casing. A 1.5M oscillator
was hard coupled to a Bauer BG-40 top drive drill rig
that was utilized to remove the shaft material from
within the temporary casing. After the casings were
excavated, permanent casing segments were hoisted and
welded over the shaft, the temporary oscillator casing
was extracted, the reinforcing steel cages were placed
and the shaft concrete was pumped into the permanent
casings.
In addition, six (6) 30” diameter shafts were drilled
in rock at Abutment 7 with the Bauer BG-40 drill rig
to a depth of 52’.
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