secant pile construction - polymolding...

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Secant Pile ConstructionOSIS Augmentation & Relief Sewer (OARS) Phase 2 Shafts # 3, 4 & 5

DFI – ADSC Drilled Shaft SeminarSupport with Confidence

July 11-12, 2013

Secant Piles Construction

• Structural foundation element consisting of overlapping piles forming a continuous wall.

• Reinforced concrete (rebar cages or soldier piles).

• Depth depends upon final design & soil and equipment characteristics.

• Piles diameters usually based on metric tooling size. Typically 760, 880, 1000 and 1180 mm are used. Other sizes are available.

• Secant piles walls to be cantilevered or braced. Any geometric shape is possible. The more unique the shape the more difficult the bracing system becomes.

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• Selection of secant piles vs. other earth retention support systems is based on:– Available work space / site logistics

– Layout of wall

– Impact restrictions on adjacent structures

– Design parameters (stiffness of wall, cutoff requirements…)

– Material handling requirements

– Excavation capabilities in difficult soil conditions


• Sequence of construction– Guide‐walls installation

– Primary or lagging piles installation• Sectional casing rotation in advance of auger removing soil inside of the

casing– Dry or wet drilling depending upon soils conditions

• At drilling completion, cleaning of pile bottom & placement of concrete – Free fall placement in dry condition and with a tremie pipe in wet conditions

• Extraction of casing at pour completion

– Secondary or closing piles installation• Sectional casing rotation in advance of auger removing soil inside of the

casing– Dry or wet drilling depending upon soils conditions

• At drilling completion, cleaning of pile bottom & placement of reinforcement followed by concrete

– Free fall placement in dry condition and with a tremie pipe in wet conditions

• Extraction of casing at pour completion

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• Sequence of construction– Guide‐walls installation


• Sequence of construction– Primary or lagging piles installation

• Piles typically un‐reinforced

• Lower strength concrete can be used. Dependent on design and final

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• Sectional casing rotated ahead of auger cleaning inside of casing



• Sectional casing rotation ahead of auger cleaning inside of casing

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• Sequence of construction– Secondary or closing piles installation

• Piles are reinforced using rebar cages or soldier piles

• High strength concrete is typically used

Secondary Piles

Primaryiles



• Design may required all piles to be reinforced, in that case the lagging piles will be poured using structural concrete

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• Piles overlap is critical to guarantee continuity of wall

• Overlap is depending of depth of drilled piles and drilling verticality tolerance

Secant Piles Construction• Sequence of construction

– Secondary or closing piles installation• Load bearing caissons can be easily incorporated into secant wall

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• Case History

Project: OSIS Augmentation & Relief Sewer (OARS) Phase 2 Shafts # 3, 4 & 5

Project Information: 397 Each – 1180 mm Shafts

3 independent sites located approximately ½ mile from each other

Each secant pile wall system comprised of an drop shaft and approach channel.

Each secant pile for the access shaft was keyed 5’ into shale bedrock.

Average Secant Pile Drill Length was 62’.

OARS Phase 2 Case History – Shaft Locations

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OARS Phase 2 Project – Subsurface Profile

Drop Shafts: Secant Pile Compression Ring Design

All 4,500 psi Concrete

No reinforcement required for design as long verticality tolerance met, < 0.5% plumbness.

Reinforcing placed anyway due to grout pipe requirement for future Subcontractor’s work.

Seal of 5’ into Shale adequate for water cutoff.

Approach Channels: Internally braced excavation secant pile wall system.

W Section Placed every secondary pile.

4,000 psi concrete used for secondary piles, 2,500 psi concrete used for primary piles.

Seal of 5’ into Shale adequate for water cutoff.

OARS Phase 2 Project – Basis of Design

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OARS Phase 2 Project – Shaft 3 Layout

85 each Secant Piles @ 53’ Long



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OARS Phase 2 Project – KODEN Ultrasonic DeviceVerticality Control

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OARS Phase 2 Project – Jean Lutz GyroscopeVerticality Control

OARS Phase 2 Project – KODEN Ultrasonic Device Output

Pile #17B:Pile Depth = 57.83ftDeviation in x' direction = .78inDeviation in y direction = 1.57inTotal deviation = 1.75 < 7.08in = accepted

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OARS Phase 2 Project Photo’s


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OARS Phase 2 Project Photo

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QUESTIONS ?


secant pile construction - polymolding...

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