11 Key Advantages and Disadvantages of Secant Pile Walls | Applications And Uses of Secant Pile Walls
What is a Secant Pile Walls |Advantages and Disadvantages of Secant Pile Walls | Secant Pile walls Vs Diaphragm Wall
What is a Secant Pile walls
Secant pile walls are a traditional method of constructing a retaining wall, especially in areas with hard soil or when building a wall facing a large excavation.
Secant pile walls are made from steel or timber. They are built according to the ground’s slope or a foundation’s level and the top of the wall is perpendicular to the ground.
Secant pile wall is an engineered retaining wall made up of interlocking concrete units that are enhanced with helical piles of steel.
The pile helps establish the lateral stability of the wall. The wall is made up of a molded concrete unit with an internal row of steel helical piles.
The piles are aligned vertically and embedded at an angle which provides lateral stability for the wall.
They are vertically aligned and a moulded concrete unit is placed around the outside of the steel pile to form the wall.
Applications And Uses of Secant Pile Walls
Secant pile walls are used in several ways:
- Retaining walls in large excavations: Secant pile walls are used to retain the fill from large excavations, as for example, when building tunnels or basements or when excavating underground passages.
- Retaining walls in areas with hard soil: The secant pile wall is used to construct a retaining wall that is perpendicular to the ground. It helps determine the proper heights of embankment and walls, which in turn help control water seepage.
- Retaining walls against liquefaction: Secant pile wall can be used in areas where liquefaction is likely to occur because of large earthquakes and heavy rains or where foundations are weak.
- Retaining walls in areas with high slopes: Secant pile wall is commonly used to construct retaining walls that face large slopes.
- Cohesive soil wall: The cohesive soil wall technique can also be used for constructing secant pile walls and is made up of a concrete or steel frame filled with a layer of compacted gravel on the outside.
- Depression retaining walls: These are made mainly for retaining the soil in depressions created by construction activities such as building footings, tunnel entrances, embankment, foundations etc.
- As cut-off barriers: This design is also appropriate for holding fine sands and very soft wet ground, and it can be utilized for cut-off barriers like cofferdams. The secant piled wall’s goal is to ensure that the ground or composition behind the wall is securely and safely maintained in place in the face of lateral and downward pressure from the retaining structure.
Advantages and Disadvantages of Secant Pile Walls
Advantages of Secant Pile Walls
The main advantages of secant pile walls are:
- Less noisy construction: Secant pile wall construction is less noisy than the traditional method of pile wall construction;
- Fairly simple construction: Secant pile wall construction requires less time than pile walls constructed in a trench; and
- Good flexibility: Although secant pile walls are made of concrete, they are designed to conform to the ground’s surface and will not sag over time.
- Increased wall stiffness compared to sheet piles: Secant pile walls are stronger than conventional methods of retaining wall construction.
- Proper alignment: The piles are provided with an angle that provides lateral stability to the wall. Secant pile walls have a good alignment that will not deform when loaded by soil from below or seismic movement. Secant pile walls can also be used to retain the soil where it is necessary to resist a certain amount of unbalanced pressure or provide lateral stability against seismic movements.
- Can be installed in difficult ground (cobbles/boulders): The secant pile wall can be installed in areas with cobbles or boulders. This is a big advantage compared to other methods of construction.
Disadvantages of the secant pile wall
The main disadvantages of secant pile walls are:
- More expensive compared to sheet pile walls: The main disadvantage of secant pile walls is that they are more expensive than sheet pile walls.
- Difficult to get total waterproofing: The method of waterproofing secant pile walls is not completely satisfactory as the concrete faces that are in contact with the ground can get wet and cause problems.
- Difficult verticality tolerance for deep piles: The verticality tolerance of deep steel helical piles has been found to be less than that of sheet pile walls.
- Lower earthen embankment strength: Secant pile walls may not be strong enough to resist water pressure and they may also disintegrate after heavy rains due to soil erosion etc.
- Watertightness: The method of waterproofing secant pile walls is not completely satisfactory as concrete faces in contact with the ground can get wet and cause problems.
Secant Pile Walls FAQs
1. What is secant pile wall?
Secant pile walls are built using interlocking reinforced concrete piles. Secant piles are reinforced with steel rebar or steel beams and are built by drilling or augering through the mud.
Primary piles are installed first, followed by secondary piles, which are built in between primary piles once the latter have gained adequate strength.
Pile overlap is usually in the range of 3 inches (8 cm). There is no pile overlap in a tangent pile wall since the piles are built flush to each other.
2. What is secant pile wall used for?
Secant piles are a type of foundation system that is often used in areas where there is a high-water table.
Secant piles typically consist of two parallel rows, with the second row being offset from the first by an amount equal to half the pile length.
The purpose of this design is to allow for drainage between the piles and prevent water from saturating them.
3. Are secant piles waterproof?
A secant pile is a type of construction that is used to stabilize an area around the base of a tower.
Secant piles are made up of steel pipes, and they are driven into the ground at angles to form a triangle with the tower as one side.
These piles can be cut off on top or bottom so they resemble wedges, but this isn’t always necessary.
Secant piles are made of water-resistant materials against water seepage.
Secant walls can be utilized to create a continuous watertight wall, which can be useful in the construction of basements and subterranean parking garages.
4. How are secant piles constructed?
Secant Pile Walls are built by intersecting reinforced concrete piles. Secant piles are strengthened with steel rebar and built in a variety of ways. Secant pile walls are built using cast-in-place techniques.
They are built using the female/soft piles first, followed by the male/hard piles, which intersect the female/soft piles.
Secant walls are made of water-resistant materials.
Secant pile walls are commonly used as retaining structures and support systems for deep foundations, as well as retaining elements and load-bearing walls for engineering works.
A secant pile wall is a less expensive alternative to a diaphragm wall.
5. What is the difference between secant pile walls vs diaphragm wall
Diaphragm walls are a type of foundation system that uses an engineered structural system called a diaphragm to provide vertical support for a structure or a building.
A diaphragm wall is a building element with an airtight membrane that divides one space from another.
Diaphragm walls are constructed of either concrete or steel beams on either side of the ground, with cement grout used to fill any voids between the beams.
They are strengthened in the middle with an interlocking steel frame which is pumped into place.
Secant pile walls on the other hand are made up of reinforced concrete or steel piles and are typically used to create retaining walls or support structures for deep foundations.
Secant pile walls are built using cast-in-place techniques.
Unlike the interlocking diaphragm wall, a secant pile wall is constructed by drilling or augering through the mud, with the primary piles made first, followed by secondary piles which are built in between primary piles once the latter have gained adequate strength.
6. What is the difference between tangent pile and secant pile?
Secant pile walls are constructed by erecting a series of intersecting reinforced concrete piles.
Steel rebar cages or beams are used to reinforce secondary piles. Tangent pile walls are built in such a way that no piles overlap.
7. What are secant piles used for?
A secant pile wall is made up of overlapping (secant) piles that are used to build structural or cutoff walls and achieve the necessary water tightness.
Steel bar or beam reinforcement can be incorporated into the design, and anchors can offer additional lateral support if necessary.
8. Are secant piles load bearing?
Secant piled walls are embedded retaining wall structures that are primarily used to enable for deep excavation in water-filled ground situations.
Piles are installed in a specific sequence to build the walls. Soft (unreinforced) piles are erected initially, followed by hard (reinforced) piles that overlap and cut through the two soft piles on either side.
When the wall is finished, it will be a ground and water retaining wall that can also be load-bearing wall.