NARRATIVE BORED PILE CONSTRUCTION METHODOLOGY
(this is specific Bored pile Methodology in one of
our bridge foundation piling works)
By : Dionysus Maguayan
The Technology of Bored piling is basically very simple and consists of
the following operations:
a. Location Setting Out and Referencing
The ground must be level or undisturbed before
setting out the center points of the bored pile location. This prevents
difficulty in placing center marks. This
also ensures convenience in the positioning of the equipment such that
incidents of overturning and the like are prevented.
b. Driving of Permanent Casing
After the center marks have been established, the
permanent steel casing will be driven. The steel casing is used so that the
topsoil, which carries overburden loads such as the equipment weight, excavated
soil and others, will not collapse. The steel casing also serves as guide for
the drilling bucket and to make sure that the center of the hole will not move.
c. Boring/Drilling Vertical Hole
For boring a hole, an RT3-S rotary drilling machine will be used. The
machine is mounted on a LINKBELT Crawler Crane Capacity 45 Ton Model
LS-1O8-BJ. Before the start of drilling,
we make sure that the kelly bar attached to the drilling machine is vertical to
ensure that the drilled hole is precisely perpendicular to the level ground.
d. Cleaning of Bored Hole
After drilling the vertical hole, the drilling
bucket will be replaced by a cleaning bucket. This process will ensure that the
bottom of the hole is free from settled silt or loose materials. Initially, these settled loose materials came
from the suspended materials acquired during drilling.
e. Fabrication and installation of rebar cages
The fabrication of reinforcing bar cages is done
by segments. The fabrication is composed of making spiral ties, stiffening
ring, and spacers. After fabricating the stiffening ring, the vertical bars
will be welded around the ring forming the rebar cages. Then, the spiral ties will be installed
depending on the specified pitch or spacing.
These are tied to the vertical bars by means of the common wire. Lastly, the spacers will be attached on the
segmental fabricated rebar cages. The completed cages will be ready for
installation after cleaning the bored hole. The splicing of segmental cage is
performed after the first segment is brought down the hole. Welding works will follow to execute the
splicing of the cages. This process is
repeated until the last segment is installed.
f. Pouring of Tremie Concrete
The first step is to position the platform
centered to the bored hole. Placing the
tremie pipes reaching the bottom of the hole follows this. After finishing the set-up, a cloth, sack or
any light material will be placed at the chute.
This means that the first concrete that reaches the bottom will be the
first concrete to come out of the bored hole.
Tremie pipes will be maintained embedded to fresh concrete at minimum of
two (2) meters and a maximum of six (6) meters. Extraction of tremie pipes is
done if the embedment reaches maximum but before extracting, tamping is
performed. After the tremied concrete
reaches the pile head elevation, an extra length of at least two (2) meters is
added to the pile head. This is done so
that dirty concrete will come out, thus, assuring that the pile head has pure
fresh concrete.
BRIDGE BORED PILING WORKS
Pictures of Bored piling works (not in chronology)
Pictures of Bored piling works (not in chronology)
Settting Out and installation/driving of temporary steel casing
Bore-hole drilling
Slurry (bentonite) preparation or (depending on soil conditions)
Tremie pipe concreting (tremie pipe in the bored hole)
Ultrasonic testing(using embedded 2" pipe)
