Displacement Piles - Types & Features

Displacement piles (DP) are pile construction technology whose main objective is to install piles without excavating the ground. As per PN-EN: 1997-1: 2008 standard, displacement pile construction involves:

1. Hammering in
2. Pressed in
3. Vibrated 
4. Executed using spreading drills

Displacement piles are increasingly used with a new variation in materials and construction techniques. It is also referred to as driven piles.

Principle of Displacement Piles

The basic principle behind displacement piles is the assumption that the soil displaced by the pile or the driven casing increases as the lateral stresses in the surrounding soil. This is caused by:

• Densification and prestressing cohesionless and unsaturated soil
• Formation of excess pore water pressure in saturated cohesive soils.

The design consideration and construction details are given in EN 12699-2000 - Execution of Special Geotechnical Works.

Types of Displacement Piles

As per BS 8004: 1986, displacement piles can be:

1. Large Displacement Piles: These are piles comprising solid sections with closed-end or hollow sections with a closed-end, that are driven or jacked into the ground and displace the soil. All driven and cast-in-place piles come under this. This initiates piles with large diameters.
2. Small Displacement Piles: These are piles that are driven or jacked into the ground, but have a smaller cross-sectional area compared to large displacement piles. They include rolled steel H or I steel sections. 

Consolidating the above-mentioned types, the two major types of displacement piles are driven piles and screw/helical piles. Each type has its own classification, based on the material used for pile construction.

Sl.no	Types	Construction	Suitability
1	Driven Piles	Piles are driven or hammered into the ground by means of vibration. Precast Piles are constructed Using •R.C.C Concrete •Steel •Timber •Plastic (Pipes/Sheet)	•non-cohesive soil •Soil with the high water table •Contaminated Soil
2	Drilling Piles	Here, the pile is constructed in the ground using drilling tools. Unlike driven piles, the drill piling does not cause vibration or noise during the operation.	•Masts, Signs, and Retaining Structures

Based on this there are different types of displacement piles as shown in the below flowchart.

Fig.1. Classification of Displacement Piles

Read On: Auger Screw Piles/Drilled Displacement Piles

Displacement Piles Construction Method

There are different methods used for the construction of displacement piles, which includes:

1. Atlas Pile - Screw Piles
2. Fundex Piles - Screw Piles
3. SVV-Piles - Screw Piles
4. Frankipfahl Piles - In-situ concrete-driven piles
5. Grouted Displacement Piles- HPD Piles/Ductile Piles

Read More On: Foundation Engineering