Secant piles

The main disadvantages of secant pile walls are: 1. Verticality tolerances may be hard to achieve for deep piles. Total waterproofing is very difficult to obtain in joints. Increased cost compared to sheet pile walls.

Secant pile walls are formed by constructing intersecting reinforced concrete piles.

Primary piles are installed first with secondary (male) piles constructed in between primary (female) piles once the latter gain sufficient strength. Pile overlap is typically in the order of inches (cm). Secant or tangent piles are columns constructed adjacent (tangent) or overlapping ( secant ) to form structural or cutoff walls. From soil mixing to drilled shafts, Hayward Baker draws on its complete suite of techniques to optimize the design and construction of these walls.

A secant pile wall is a type of bored pile retaining wall consisting of a system of interlocking reinforced concrete piles. Secant-piled walls can be constructed using either Continuous Flight Auger (CFA) or Bored Cast-in-Place (CIP) methods. Like diaphragm walls, secant pile walls can be used as permanent shoring solutions and load bearing basement walls under high-rise structures.

RECON forms secant pile walls by constructing a series of interlocking and contiguous drilled shafts with primary piles and secondary piles that are made of soft concrete and become interlocked when set. Typically, primary (female) piles are cast in situ, leaving space in between them. This is followed by secondary (male) piles being cut into the primary piles to form a continuous wall, generally with a typical interlock of around 1mm. The design can incorporate steel bar or beams for reinforcement and anchors can provide additional lateral support, if needed. Like diaphragm walls , secant pile walls can be used as permanent shoring solutions and load bearing basement walls under high-rise structures.

Secant piles are relatively impermeable and can be used to control the flow of groundwater into an excavation and limit draw down outside the excavation. This technique is suited for dense, urban environments. Walls are constructed by the sequenced drilling and construction of overlapping, reinforced concrete piles. They are formed with intersecting piles of concrete forming a continuous structure. Secant walls hold soil and rock back, even in unstable soil conditions, while preventing water flow into the excavation area.

The purpose of this is to ensure that the strata behind the wall would remain undisturbed during construction and to ensure safety from the risk due to high lateral pressure. Overlapping ( secant ) piles or adjacent (contiguous) piles are installed to form structural or cutoff walls. Secant piled walls are embedded retaining wall structures mainly utilised to allow deep excavation in water charged ground conditions. The walls are constructed by installing piles in a predetermined sequence.

A disadvantage is then the requirement of very powerful machines and big demands for accuracy.

Complete design and analysis of pile walls can be performed by programs. CONSTRUCTION OF SECANT PILE WALL This pictorial guide illustrates the construction sequence of a Secant Pile Wall. This type of retaining wall was used for the construction of Chinatown Station on the North East Line (NEL).

Safety Measures The Land Transport Authority (LTA) accords top priority to safety. The volume of concrete placed at each hole was typically around cubic yards (cubic meters), which is about more than the theoretical volume of a 1ft (m) deep, 3. The secant piles were tremie concreted with the casing progressively extracted as the concrete was placed.