This document summarizes the process for constructing secant piles for a microtunnel shaft. It involves first constructing guide walls as reference points. Then female piles are drilled and concreted without reinforcement cages using lower grade concrete. Male piles are drilled between female piles, cutting through them. Reinforcement cages are installed in male piles before higher grade concrete is placed continuously from the bottom up via a tremie. The casing is gradually extracted to allow the concrete to rise above the cutoff level.

1. SCPX Project – Kura West Kazakh
Microtunel Construction

3. 1. Guide Wall Construction
2. Secant Pile Construction
Reinforcement cage installation (only in male piles)
Placement of concrete & Extraction of Casing
Milestones

4. Guide Wall Construction
Scope of Guide Wall Construction is:
• Surveying & excavating trenches for guide walls;
• Levelling & Placing Lean Concrete;
• Reinforcement & formwork installation;
• Placement of concrete;
• Striking of formwork & Backfilling.
This construction element will act as reference points for pile centres. Please see figure for plan and cross sectional view of guide
wall. In order to resist drilling rig own weight and down force, guide wall height is decided as 1meter.
Backhoe loader will excavate trenches for the footprint of guide walls including working space for formwork

5. Guide Wall Construction
Port Baku Tower Project – Guide Wall Construction for Secant Pile

6. Secant Pile Construction
OPERATIONAL SEQUENCE
• Driving the Casing;
• Drilling of Piles;
• Reinforcement cage installation (only in male piles);
• Placement of concrete and Extraction of Casing.
Following casting of the guide wall a piling mat was constructed inside the shaft ring.
There are two different kinds of piles in SCPX Kure West River Crossing Shaft secant piles. These are
30pcs female piles which will be constructed with low grade bentonite added concrete (C12/15),
without reinforcement cage; and 30pcs male piles which will be constructed between two adjacent
female piles by cutting them through, with high grade concrete (C30/37) and with reinforcement cage.

7. Secant Pile Construction
OPERATIONAL SEQUENCE
In a secant piled design, there are two main types of elements to be constructed.
These are male piles and female piles. Main differences between these piles are
drilling conditions, reinforcement and concrete grade.
A. Female Pile Drilling
• Female piles will be drilled as ordinary piles. Pile boring (drilling) will be carried
out by using the piling drilling rig. Casing and drilling tools will advance in
natural soil until end of drilling. During pile boring operations, different drilling
tools/attachments (bucket, auger, rock auger, core barrel) will be used
depending on the nature of soil encountered. Depth of the pile borehole will be
checked manually by a measuring tape and automatically by drilling rig’s own
depth meter. Drilling will stop at the +179.60 el. Concreting will be done same as
explained below, but without reinforcement cage installation and with low
grade bentonite added concrete.

8. Secant Pile Construction
B. Male Pile Drilling
• A male pile will only be constructed between two
finished neighbour female piles by cutting both of
them through until pile bottom. Cutting of female
piles will be done by the casing cutting shoe and
diamond tooth augers. Concrete grade, type and age
of the female piles are very important factors
considering firm and vertical construction of male
piles. Optimum age for a female pile to be cut is 3 to
5 days after casting. After 5 to 10 days are the
possible days also, but after 10 days female pile
concrete become harder to cut and increase risk of
inclination. While female concrete strength
(resistance against abrasion, crushing) rises, tendency
of inclination in male piles rises because drilling tool
will always lean towards to more soft medium. To
balance the resistance as much as possible against
soil, female piles will be casted with bentonite added
concrete. Other than cutting concrete of female piles,
drilling will be continued and finished similar with
female piles.

9. Secant Pile Construction
Reinforcement cage installation (only in male piles)
Reinforcement cage will only be installed in
male piles. Female piles will be constructed
without reinforcement cage. All
reinforcement cages will be inspected by
Client prior to deem as completed.
. Two hooks as detailed in document CS-
MX1217-CV-DTL-0005-001 - Kura West (AZ)
River Crossing - Drive Shaft Secant Piles.
Whole cage will be suspended from here on
to the casing top via 2 pcs 32 mm rebar.
This fixing job is going to be repeated for all
cage parts until req. length of the cage is
achieved as shown in the drawings unless
drilled depth is more than designed depth.

10. Secant Pile Construction
Placement of concrete & Extraction of Casing
Concreting of the pile will start and continue without any
interruption to form a continuous full cross-section of the
pile.
The tremie pipe with watertight connections will be
lowered inside the pile borehole extending down to base
of the pile borehole. Tip of the reinforcement cage shall
be open and un-bended to lower the tremie until the end
of hole.
C30/37 concrete which has a slump value between 19cm
to 21cm to be placed by tremie in one continuous
operation and shall not be discharged freely into the
water. Concreting will be done by pump connected to
tremie and pile/casing will be filled with concrete up to
the top of casing level. Clean concrete (concrete with
coarse aggregates) will be seen to be overflow before
stopping concreting.

11. Secant Pile Construction
Placement of concrete & Extraction of Casing
Tremie will be lifted in parallel to concreting and during lifting min. Three meters tremie will be within concrete at all
times. After completion of concrete tremie will be dismounted from the pump, the casing will be lifted 2 m from
platform level and at this height casing extraction will be stopped. Concrete will be added from top by concrete pump
to fill the casing again to the top level of casing. This will provide enough head of concrete and will make sure that
when casing is removed the concrete will outflow and a proper level of top concrete level will be obtained. The exact
height should be confirmed with site performance and can be reduce/increased to achieve the target concrete
finishing level.

12. Secant Pile Construction
Placement of concrete & Extraction of Casing
• The casing will be removed in parts (4 meters and 5
meters) as concrete rises inside the casing. As nature of
the work, concrete level will drop as casing is removed. It
is critical not to let concrete level drop below casing
bottom. Before removing last part of the casing and
tremie, top of the pile will be filled with concrete from
mobile pump hose, from inside. This will ensure concrete
to remain above cut-off level after casing removal.
• Concreting of female piles has two differences from male
piles; concreting will be done without reinforcement
cage installation and concrete grade will be lower than
male pile’s concrete grade. Both intentions are for to
allow male piles to cut through female piles.

13. Secant Pile Construction
Placement of concrete & Extraction of Casing
• Fresh mixed bentonite slurry will be added in to the
mixer not more than 5% in weight of cement at the
concrete plant. Addition of bentonite in to the female
piles will not cause any degradation in water proofing in
female piles because slurry will be thoroughly mixed
with fresh concrete before placement to avoid
heterogeneous accumulation and concreting will be
done similar with the male piles using tremie pipe from
bottom to the top, in one continuous operation. Casing
will be extracted in two or more stage to ensure
sufficient concrete head to remain above cut-off level.

14. Secant Pile Construction
Placement of concrete & Extraction of Casing
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