What is Secant Piles?

• Formed by constructing overlapping piles to produce a continuous wall.

• They are constructed by either drilling under mud called augering.

• The depth depends on the final design, the soil and appropriate equipment to be used.

• Secant piles are great for permeable grounds with watery conditions.

HOW SECANT PILES

CONSTRUCTED?

• The primary piles (laggings) are installed

first & filled with lean concrete.

• Then, the secondary piles is constructed in

between primary piles formed in structural

concrete.

• Pile overlap is usually 8 cm & the diameter

of each pile typically range from 760mm,

880mm, 1000mm or 1180mm.

PRIMARY SECONDARY

REINFORCEMENT

WITHIN THE PILES

• Secondary piles are usually reinforced with

either steel rebar or steel beams. Its less

common to have both piles reinforced.

• Steel beams are used when it involves the

use of weaker than normal concrete.

IN DEPTH EXPLAINATION

Primary/ Lagging piles installation

• Not reinforced

• Uses lean concrete

depending on the

final design.

Primary/ Lagging piles installation

Primary/ Lagging piles Installation

Secondary/ Closing piles installation

• Secondary piles are reinforced with rebar.

• High strength structural concrete is typically used

• Process is repeated with the secondary piles. Driving

the casing into the ground and augering it .

Secondary/ Closing piles installation

SUMMARY OF THE PROCESS

1. GUIDE WALL

INSTALLATION

2. CASE

INSTALLATION3. AUGERING &

REINFORCEMENT

4. CONCRETE

SECANT PILES

ADVANTAGES • Increased alignment flexibility in

construction.

• Increased wall stiffness compared to sheet piles.

• Can be installed in difficult ground (cobbles/boulders).

• Produce less noise during construction.

DISADVANTAGES

• Vertical tolerance may be hard to achieve for deep piles.

• Total waterproofing is very difficult to obtain in joints.

• High cost compared to sheet pile walls.

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