Piling can be used in certain situations where it is not safe, practical or economical to excavate for traditional foundations.
This may be due to:
- the nature of the ground, eg loose backfilled ground, water bearing soils, soft clays incapable of taking any significant loading
- local influences such as deep penetrating tree roots in shrinkable clay soils leading to desiccation of the upper layers.
The basic function of the pile is to transfer the building load to greater depths to achieve the required load bearing capacity, thus overcoming the problems in the upper stratum.
Purkelly can design and construct piles or complete foundation solutions consisting of piles and beams or raft slabs to suit almost any site conditions with the minimum fuss and disruption to the owner or builder.
We also offer a specialist contiguous piling design and build service for the construction of piled retaining walls for new basements.
All of Purkelly’s piling equipment is designed for use where there is restricted access or limited headroom. It will operate within domestic properties if required, and is also powerful enough to compete with larger machines when working in open sites.
Let Purkelly design and construct your foundation package, or if you already have a design and a groundworker on board, we will happily construct the piles only. Purkelly piling services offer:
Engineered solution to provide maximum value for money.
Purpose designed machinery and experienced professional teams ensure excellent productivity rates.
Health & Safety:
No deep trenches posing risks to operatives, occupants and visitors to site.
Piling is designed to use a minimum amount of materials, ie concrete and steel and produces very little spoils. The environment benefits from reduced energy usage in materials production, reduced vehicle movement in transporting material and spoil, and reduced excavation results in less spoil to go to landfill sites.
1. Auger bored piles
These are used in cohesive clay soils where there is no groundwater and the bore remains dry and open on completion.
This type of pile takes it load bearing capacity from the friction generated between the clay and the surface area of the pile shaft, and therefore different loading bearing capacities can be achieved by varying the diameter and length of the piles.
In shrinkable clay soils that are likely to be affected by the action of tree roots, the upper 3-4 m of pile can be sleeved to help reduce the affects of “ground heave”.
Types of load that these piles are capable of carrying are:
Diameter Load Capacity
200 mm up to 150 KN
250 mm up to 250 KN
300 mm up to 350 KN
350 mm up to 400 KN
Auger bored piles can also be used to form retaining walls by forming a series of piles with a minimal gap between them. This is known as a contiguous piled retaining wall and can be a useful tool in the formation of basements, swimming pools, etc.
There are also some variations of the auger bored pile which enable them to be used where there are non-cohesive or water-bearing soils overlying the clay substratum.
Temporary Cased Bored Piles
In order to overcome these problems we can use temporary steel casing which is installed by the piling rig as the augers are drilled into the ground. The casing is screwed in through upper layers and into the underlying clay where it forms a seal with the clay and prevents the water and granular materials entering the pile bore. The augers then proceed drilling into the clay which is brought up through the casing forcing any water or granular material out of the casing at ground level and forming on open pile bore. The pile bore is then concreted and the casings withdrawn as the concrete is poured, keeping the concrete above the bottom of the casing to make sure there is no collapse of the pile bore and the integrity of the pile is not compromised.
Another method of installing bored piles in non-cohesive, or water bearing soils would be to use our mini-CFA or hollow stem auger piling.
Purkellys in-house chartered civil engineer will design the piles to suit the loads, ground conditions and applications on each project.
2. Steel-cased Driven Piles
These piles are used in situations where an open bored pile cannot be used:
- due to loose ground conditions such as backfilled or made ground overlying a decent bearing stratum
- where there is groundwater present
- if the soils are too soft or weak to achieve the friction required to carry the loads required.
This pile is formed by driving a steel tube, crimped at the leading end, down through the problem ground into denser stratum below capable of carrying the load.
The tube is driven by means of a vibratory air hammer or a drop weight and is driven to a pre-determined set, eg 3 mm per drop weight blow or 25 mm per minute in the case of the vibratory hammer. Steel reinforcement is then placed into the tube and the tube filled with concrete to form the completed pile.
Driven piles are end bearing and thus derive their load bearing capacity mainly from the density of ground in which a pile terminates. Obviously the capacity also increases with diameter.
Typical load bearing capacity of the driven piles Purkelly offer are:
Diameter Load Capacity
150 mm 90 – 100 KN
220 mm 150 – 180 KN
As in the case of bored piles, our engineer will design the piles required for any particular project.