PILING & PILE FOUNDATIONS

Piling

Piling is a term basically used in deep foundation works in construction industry. Piles are either use for the foundation of super structures (buildings, bridges, towers, etc.) or as supporting deep excavations (shoring by sheet piles, secant piles, contiguous bored piles, etc.) or in special cases like installation of sand piles as vertical drains for the soil consolidation/ soil improvement or sometimes in other areas which are not listed here. Piles may be by using wood, concrete, steel or some other material. And the installation method may be by bored in-situ cast, precast and hammer driven, etc.

Figure: Marine sand piling barge

Pile Foundations

Piles are the most commonly used type of deep foundations where vertical distribution of the load takes place. There are different types of piles and they can be classified based on the type of the material of piles, method of installation or the amount of soil displaced during installation of the pile. As the geotechnical and structural performance of the piles largely depend on the method of installation, classification of the piles based on the method of installation is very common. 

Following the classification of the piles based on the method of installation, piles can be grouped into the following categories:

1.    Bored and cast in situ piles

2.    Driven piles

3.    Jacked piles

4.    Screw piles

5.    Continuous flight augured grout and concrete injected piles

6.    Jetted piles

      etc.

Both bored & cast in situ and the driven piles are common in construction.

Bored Cast In-situ Piles

 A bored and cast in situ pile is constructed by drilling a hole into the ground with or without a casing and filling the hole with concrete after inserting a reinforcement cage. Currently the most common method using for drilling is the use hydraulic rotary drilling machines due to speed, accuracy or verticality and the possibility of identifying soil or rock layers easily with depth. In the operation of bored piling, when drilling with short augers or buckets different types of tools such as soil auger, soil boring bucket, rock auger, rock boring bucket, core barrel, etc. are used depending on the soil or rock strata existing. 

Driven Piles

 Driven piles or  are basically pre-cast with a sharp steel head to facilitate easy installation with a vibro or drop type hammer. Driven piles are not suitable for areas with rock boulder locations need to drill through to provide sufficient skin friction.

Continuous Flight Auger (CFA) Piles

 Continuous flight auger piles are a installed by an auger machine consists of threaded type shaft. Drilling is carryout with water supply though the shaft and removal of soil by the mechanism of threaded shaft. Then concreting in the same process while taking the shaft out from the drilled hole. This is much faster than the bored and cast insitu piling.

Soil Improvement by Piling

There are several methods using in soil improvement using piling.

1. Vertical drains (Sand piles)
2. Soil replacement (clay/ peat soil replace with hard soil or building debris)
3. Jet grouting (Grout piles)
    etc.

Sand piling process

Soil replacement

Jet Grouting process

Shoring for Deep Excavation by means of piles

Different types of piling techniques are used in shoring work for deep excavations.

1. Sheet piles
2. Secant piles
3. Contiguous bored piles
    etc.

 Sheet Piling

 Secant Piles

 Contiguous bored piles