This month we are looking at Piled foundations which are one of the most important items when it comes to structural design. As structural engineers, it’s our job to make recommendations based on the knowledge we have, and we’re going to be sharing that knowledge today. This builds on our post about geotechnical investigations back in 2018.
It begins with bore holes, which should be below the deepest pile in the design scheme. We’ll take a deeper look at pile testing in all of its different forms in a future article, but in the meantime, we’re going to deliver on a promise we made in our post on foundations in our March article last year. It’s time to take a look at piled foundations.
By definition, “a pile is a long cylinder of strong material such as concrete that is pushed into the ground to act as a support for the structures built on top of it.” One of the most common questions that we get asked is, “Where and why are piled foundations used?”
As a general rule, piled foundations are used in the following situations: 1. When there is weak soil and the layer can’t support the weight of the building above 2. When there are heavy concentrated loads, such as in high rise buildings
The two main types of piled foundations are as follows:
1. End bearing piles: With these piles, the bottom end of the pile bears into a strong soil layer (such as rock). The load of the building is transferred into the strong layer through the pile. 2. Friction piles: With these piles, the load from the building is transferred into the soil by using the full height of the pile. Essentially, the entire cylindrical shape works to transfer the forces through the soil.
On top of that, there are other types of piles, such as the following: 1. Settled and reducing piles 2. Tension piles 3. Latterly loaded piles 4. Piles infill
Piles can be constructed in a number of ways and the best approach for you depends on ground conditions, site access, durability requirements, programme, pile capacities, costs and other factors. Here are just a few of the most common.
Displacement Piles 1. Pre-formed displacement piles 2. Driven and cast in place displacement piles 3. Screw casts in place displacement piles
Non-Displacement Piles 1. Board cast in place piles 2. Partially pre-formed piles 3. Grout or concrete intruded piles
In general in the UK, the structural engineer will provide the piling contractor with the loads for each pile for the building. Then the piling contractor will design the piles for the project based on a combination of these loads and the geotechnical investigation report and soil parameters.
Here at LSY, we are working on various projects where piling is being adopted if you ever need any help or advice then don’t hesitate to get in touch with us to find out more. We look forward to working with you!