January 25, 2006:
Adventures with drilling and the jackup
barge
Of all the amazing things that I have learned during the building of
the Ravenel Bridge and the unbuilding of the Grace and Pearman Bridges,
today was up there at the top. It was all Mickey Roger's fault. He
suggested I learn a bit about drilling from the jackup barge - so I spent
the afternoon with Captain Bill Freaney and his jackup barge team, Ken and
Mike King and with Mickey's drilling team:Felix Butler, Ernest Asby (better
known as Junior), Kerry Spencer and Silas Presot. And of course,
life without Sharon's taxi service is simply not much of a life. So
we started with Sharon passing what remains of the Grace and Pearman
trusses - no longer over Town Creek.
The jackup barge was standing beside C3 - the third Cooper River
pier within the Coooper River ship channel
A closer look. Now something about the jackup barge - from Capt.
Bill and Mike. The legs are 150' in lenght and at the base are
pads, 14' in diameter and 3' thick. The barge itself weights
about 1,300,000 pounds. In the belly are two preload tanks that
can each hold 350,000 pounds of water - and there are two
steering propellers. So, with the legs in the up position, the
jackup barge drives like a small ship. However when
the jackup barge wants to plant its feet, then the three legs,
controlled by a pair of racks and 4 pinions, driven by
hydraulic motor, are lowered. When they touch the bottom, the
trick is to slowly slowly lift the hull off the surface of the water
while adjusting the extension of each leg in order to maintain
a level orientation. So what happens when the river bottom is
not level. Capt. Bill has a pair of carpenter levels in his
pilot house that he watches and with inspiration, shear determination
and skill, adjusts the legs so that they sink into the mud
and establish a firm base. The trick is that the river bottom is
not level and the legs can slip - which requires what I consider
extraordinary skill in order to prevent the barge from tilting
and perhaps falling over. Here is the jackup barge fully
extended.
Once stabilized, preload tanks are filled with water, adding
additional weight to stabilize the footing. To undock, the
preload tanks are emptied whuch creating a positive buoyancy
which can pull the legs free of the bottom. Additional
positive buoyancy can be generated by emptying the preload tanks.
(And please provide any corrections to this description).
Next Calvin Konya (from
Precision Blasting Services
in Montville Ohio), Mickey
and I took the elevator from Sharon's taxi to the barge. On the left you
can see our elevator cab, suspended by the crane, slowly descending -
and on the right, climbing in.
On the way up, there was a great view of the foundation of the 1/4 mile
long Mt. Pleasant pier
You can see the correspence with the Pearman foundations
shown on this schematic
and on the barge, Mickey's team was busy finishing drilling holes
for imploding the pier.
Kerry and Silas were drilling into the pier cap. With your curious eyes,
you see some red areas have 1 hole, some have 2, 3 or maybe 7 holes.
The problem is that of lacking X-ray vision. When they start drilling
a hole, they may encounter embedded rebar - so they start a new hole
until they find a clear path for completing the hole.
Felix and Ernest were drilling into the column.
Click for a video of drilling
(13 Mb quicktime).
A closer view of Felix and Ernest drilling
Captain Bill decided I needed a reminder that I actually visited his pride
and joy and challenge
The yellow cylinders shown here are the tops of the barge legs - left leg
and right leg with the rack (vertical gear) visible
and a wider view
and back leg - you can see two teeth of the rack on the left side
Here is the hydraulic motor that drives the pinion
Kerry and Silas are drilling into the cap while Felix and Junior are
drilling into the column
When finished, these almost-martians (because of the breathing filters)
come down
while Kerry and Silas continue drilling
and when finished, return to earth
The control room - with the carpenter's level in front of Capt. Bill. A great
example of low-tech tools for maintaining the attitude of the jackup barge.
The start of our descent - which takes about 20 minutes
The view coming down is simply spectacular - here you see the roots of
D28 - D23 that were imploded over the past 2 weeks
and a closer view when we reached the river surface
Looking east - another view of the Mt. Pleasant pier foundation
and a closer view when we reached the river surface looking east. An excavator
(in the background - requires curious eyes to see it)
with its hammer is busy working on one of the pier bases.
Capt. Bill drives us to C2 where Mickey's team will drill tomorrow
and once we are in position, Bill slowly drops the 3 legs, while watching
his levels. Note the bubble is perfectly centered.
This is high tech at its highest - his right angle array of carpenter levels.
The Gunny is coming to help position us
and as the sun drops, the Gunny also has a golden hue
and finally, when the legs are in place, the surface is lifted to maintain
the 1.3 million pounds of weight on the 3 legs
Mike King prepares the ladder so that we can escape
while Ken operates the crane
and smiles
A view as we leave - note that the hull is completely elevated above the
river surface
Compare this with the 2nd photo from the top - when the jackup barge
was standing beside C-3
Now - it is positioned adjacent to C-2
and the late afternoon sun gives the Ravenel diamonds a golden hue
The Gunny takes us back to Town Creek - where our iron workers have been
working. Sparky spent the afternoon with them - stay tuned
The East Grace truss
and the West Pearman and Grace trusses