What is Piling?

Pile construction is not a new technique, it’s ancient! The history of constructing buildings using piles dates back to the 4th century BC, when people used piles for constructing foundations on weak peat soils near rivers. Many villages and towns were located in the close vicinity of lakes and rivers due to the availability of water, and, also, to ensure proper protection of the area. Therefore, the weak bearing ground was reinforced by the use of timber piles that were either manually forced into the ground, or fixed in holes that were filled with stones and sand. [1]

In Britain, there are numerous examples of the Romans utilising timber piles in construction. In mediaeval times, piles of oak and alder were used in the foundations of the great monasteries constructed in the fenlands of East Anglia. Timber, because of its strength combined with lightness, durability and ease of cutting and handling, remained the only material used for piling until comparatively recent times.

Nowadays, piling has been used in the foundations for everything, from residential houses to huge industrial warehouses and off-shore wind farms.

While materials for piles can be precisely specified, the calculation of their load-carrying capacity is a complex matter which at the present time is based partly on theoretical concepts derived from the sciences of soil and rock mechanics, but mainly on empirical methods based on experience. Practise in calculating the ultimate carrying capacity of piles based on the principles of soil mechanics differs greatly from the application of these principles to shallow spread foundations.

In the latter case, the entire area of soil supporting the foundation is exposed and can be inspected and sampled to ensure that its bearing characteristics conform to those deduced from the results of exploratory boreholes and soil tests.

As mentioned earlier, piles are primarily made from timber, concrete and steel. There is a wide range of pile types used for different soil conditions, load requirements, the space available and environmental factors. [2]

Piles can be classified into the following categories: large displacement piles (driven types), large displacement piles (driven and cast-in-place types), small displacement piles and replacement piles: [3]

Large Displacement Piles (Driven Types):

• Timber (round or square section, jointed or continuous)
• Precast concrete (solid or tubular section in continuous or jointed units)
• Prestressed concrete (solid or tubular section)
• Steel tube (driven with closed end)
• Steel box (driven with closed end)
• Fluted and tapered steel tube
• Jacked-down steel tube with closed end
• Jacked-down solid concrete cylinder

Large Displacement Piles (Driven and Cast-in-Place Types):

• Steel tube driven and withdrawn after placing concrete
• Precast concrete shell filled with concrete
• Thin-walled steel shell driven by withdrawable mandrel and then filled with concrete

Small Displacement Piles:

• Precast concrete (tubular section driven with open end)
• Prestressed concrete (tubular section driven with open end)
• Steel H-Section
• Steel tube section (driven with open end and soil removed as required)
• Steel box section (driven with open end and soil removed as required)

Replacement Piles:

• Concrete placed in a hole drilled by a rotary auger, baling, grabbing, airlift or reverse-circulation methods (bored and cast in-place)
• Tubes placed in hole drilled as above and filled with concrete as necessary
• Precast concrete units placed in drilled hole
• Cement mortar or concrete injected into a drilled hole
• Steel sections placed in a drilled hole
• Steel tube drilled down