Many large commercial, civil, and marine projects require a pile foundation to handle the significant loads necessary to erect large structures like bridges, highways, and multi-story buildings.
Foundation piles need to be installed deeper in the earth to deliver higher load-bearing capacities for larger structures or for projects where soil composition cannot support significant loads. Pile foundations also resist horizontal loads and transfer vertical loads to solid bedrock or high bearing capacity earth.
How are Foundation Piles Used?
Generally, foundation piles are only used in larger projects that require significant load-bearing capabilities. Though, other applications include projects where the site conditions feature water or compressible strata that is too weak to support large loads.
Pile foundations are carefully engineered to ensure safety standards are met at every local, state, and federal level. These plans are based on a professional soil analysis to ensure that the foundation is not beyond its maximum bearing capacity.
Each pile is surrounded by a zone of confluence in the surrounding soil. Engineers take care to place each pile far enough apart to bear the load without piles interfering with their respective confluence zones.
Some common site conditions where a pile foundation makes sense:
- If the water table is too high
- If a non-uniform load is imposed
- If the site contains compressible earth at shallow depths
- In locations where pile scouring may present future complications
- If there are deep drainage structures or canals adjacent to the job site
- If excavation cannot reach depth
- If the site experiences consistent seepage
While there is no easy answer to whether or not a project will require a pile foundation consulting with licensed engineers and performing a comprehensive soil analysis will identify the right course of action.
Every project presents its own unique issues and soil conditions, and there are a variety of pile classifications to provide adequate load-bearing support.
Piles can be classified by their design or by their method of construction. Design classifications include end-bearing or friction piles which can be used in tandem should the site require it. Construction classifications include replacement/bored and displacement/driven piles.
End bearing piles support loads by transferring the energy to solid rock or dense earth. At its fundamental level end bearing piles simply go through the weak soil and terminate at depths that can support the necessary load. One of the easiest ways to understand end-bearing piles is to think of them as columns.
Friction piles operate on an entirely different principle. They work to transfer the entire load to the surrounding earth, relying on the friction to provide robust load-bearing capacities. The greater the depth of a friction pile, the more significant load it can bear, and the capacities are directly proportional to the piles’ length.
Driven or displacement piles are among the most commonly utilized types and are popular because they are often the most cost-effective solution for large projects. They are also used frequently in marine projects like cofferdams and bridge construction.
Bored or replacement piles are drilled and filled with concrete piles that are poured on the site. These pile foundations are well suited to urban projects or spaces where headroom is limited.
How is a Pile Foundation Installed?
There are a number of factors to consider when identifying the best pile foundation for your project. These include the excavation depth, pile material, pile driving angles, local regulations, and other environmental concerns. Bored and driven piles require different installation methods, equipment, and materials.
Displacement piles are driven by pile drivers, which can be traditional diesel hammers, vibratory hammers, hydraulic, and air pile hammers. This is one of the most traditional pile driving methods and remains one of the most efficient ways to install a powerful foundation pile.
Replacement piles require drilling rigs equipped with large augers that can bore a hole deep into the earth, which is then filled with steel-reinforced concrete.
Both installation methods present their advantages and challenges, and ultimately identifying the best solution will be a coordinated effort between engineers, licensed operators, and geotechnical specialists. Proper planning and site examination will help ensure a successful project before soil is broken.
No two projects present the same site conditions, and certain considerations should be analyzed during the planning phase. Failure considerations require analysis of settling, the impact of vibrations near the site, deterioration, and other environmental features. Structural soil considerations should define the existing load-bearing capabilities and the requirements for the project’s load. Safety considerations are subject to local, state, and federal guidelines, which are implemented to ensure that a structure is constructed to code and will not experience a catastrophic failure.
With careful planning and analysis, pile foundations provide robust solutions for construction projects in sites with poor soil conditions that cannot bear significant loads. Different conditions will determine which pile foundation will deliver the bearing capabilities necessary for even the most significant construction projects.