In our last blog post we took an in-depth look at the common types of shallow foundations that you commonly see on most structures. And, as we discussed, piling falls into two main categories, Shallow Foundations and Deep Foundations.
For jobs where shallow foundations aren’t enough, piling installers need to turn to deep foundation methods and techniques. In layman’s terms, deep foundations are any foundation where the depth is more than the width, but there is a collection of piling types that fall into that bracket:
Pile Foundation
One of the most cost efficient and commonly used type of deep foundation is a pile foundation. Consisting of a long cylinder – constructed from either wood, concrete or steel, depending on the size of the structure it is supporting – pushed into the ground to act as a steady support. These types of foundations are most commonly used when shallow foundation methods are unable to reach any deeper, stable soil or rock strata. They distribute loads either by bearing or by skin friction on soil with deeper bearing capacity, when there are chances of construction of irrigation canals nearby and when it is too expensive to provide raft or grillage foundations.
Pier Foundations
These foundations are constructed using a large diameter cylindrical column which supports the superstructure and transfers large super-imposed loads to the stable strata below. The weight is transferred using an end bearing pile; unlike a pile foundation, pier foundations can only transfer load by bearing and not skin friction as they are generally shallower than pile foundations.
Pier foundations fall into two categories:
- Masonry or concrete pier – used if a good bearing stratum exists up to 5m. The nature of the soil as well as the depth of the bed will dictate the size and shape of the piers required.
- Drilled caissons – These usually refer to the cylindrical foundations. A large compressed member is subjected to axial load at the top and reaction at the bottom.
Caisson Foundations
When constructing bridges, dams, or any other construction beneath water sources such as rivers or lakes, these watertight retaining structures are used. These foundations can literally be floated to the desired location before being sunken into place. To do this the foundation is ready made in a cylindrical hollow column which is depressed into the soil up to the desired level. This tube is then filled with concrete, converting into a foundation once dried. You will see these most commonly used for bridge piers.
For more information on piling in Manchester, contact the team at Rhino Piling today and speak to one of our seasoned engineers.
