What is Piling in Construction?
Piling is a technique used to drive or bore pile foundations into the ground beneath a building. This method ensures that loads from the structure are effectively transferred to the ground, providing essential support. Pile foundations are particularly important in areas with weak soil that cannot adequately support the structure on its own.
What are Pile Foundations?
Pile foundations are slender, elongated structures composed of steel or reinforced concrete. They are designed to transfer the load from the structure through weak, compressible materials to more compact, less compressible, and stiffer soil or rock layers at greater depths. The deeper these piles are inserted, the stronger and more stable the base becomes for the construction project.
Where did Piling Come From?
Today’s advanced piling systems have their roots in ancient practices, driven by a need that has persisted for thousands of years. Early civilizations, particularly river dwellers in Switzerland around 6,000 years ago, built their homes on piles to prevent flooding and protect against attacks by elevating their structures. The Romans further developed piling techniques, using timber piles for shore works and driving them into riverbeds to construct bridges over 2,000 years ago.
Cities and towns in ancient times were often located near rivers for better communication and protection. This necessitated the strengthening of swampy soils with robust foundations, which led to the development of piling. Initially, timber piles were driven into the ground by hand or holes were dug and filled with sand and stones.
As the need for more buildings and infrastructure grew in modern times, it became essential to develop land with less stable soil. Thus, piling has remained a key method in construction, evolving to meet contemporary demands but still rooted in its ancient origins.
Fundamental Types of Piling Based on Load Transfer
The two main types of piling are end bearing and friction piles:
End Bearing Piles
End bearing piles transfer loads directly to a deeper stronger soil or rock layer below the surface.
Friction Piles
Friction piles transfer load by friction between the surrounding soil and the surface of the pile over its full length.
Various Types of Piling Based on Materials and Construction
Given the importance of pilings and the diverse needs of the locations and facilities where pilings are used it is no surprise that there are many various different types of pilings. Let’s take a look at four broad major categories of piling.
Steel Piling
Steel piles are used in a number of construction projects due to their excellent strength and ability to carry a large amount of weight. Generally speaking, fewer steel piles are required for a given project compared to piling constructed out of alternative materials because of the load bearing potential of steel piles. This often provides economic advantages to the project since fewer total piles are needed, thus reducing materials use and the time and labor involved in driving the piles.
Wood or Timber Piling
Wood piles are another popular and excellent option. This type of piling is traditionally treated with a coating in order to prevent insects from boring into the structure, thus increasing durability. Wood or timber pilings have the advantage of being relatively lightweight to transport compared to steel piling. Wood is also a renewable resource and thus offers ecological advantages that may appeal to some companies and consumers. The wood can also be treated to make it suitable for a number of different environments even if it is going underwater.
Composite Piling
This type of piling is made from different types of materials that are put together to form a single, more resilient pile. This style is particularly beneficial for marine applications since it is durable enough to withstand tough aquatic conditions. It is also completely customizable, and can be specifically designed to fit the needs of the particular project.
Concrete Piling
Concrete is incredibly sturdy, and comes in various different types. Reinforced concrete has rebar running through the pile in order to increase its strength. Prestressed concrete piles are great for having a material that is resistant against tension. Concrete piles can be created and installed at the job site, which is referred to as a “cast in situ” piling. This avoids the need to transport the piling, often resulting in cost savings. However, concrete piling can also be created off-site and then pile drived into place to allow for greater control of the finished product.
Methods of Constructing Piles
It’s important to note that the pile foundation and pile are two different things, yet they work in conjunction to ensure that piling can support strong loads. A pile foundation is typically defined as the series of columns that act as the base for structures, whereas the pile itself is the column or cylinder that aids in transferring the load to the lower subsoil.
Driven Piles
Driven piles are the classic type of pile foundation. They can be constructed with timber, precast concrete, or steel.
Timber Piles: Used mainly for coastal works, sea defenses, and jetties.
Precast Concrete Piles: Reinforced to withstand driving stresses, they are usually pre-pressed with a square or octagonal section.
Steel Piles: Available in tubular, box, or H sections. Interlocking steel sheet piles are widely used for wall construction.
Driven piles increase soil bearing capacity by compacting the soil around the pile as it is driven into the ground.
Bored Piles
Bored piles, also known as replacement piles or drilled piles, are constructed when large holes are drilled in the ground and filled with concrete. They transfer the load above ground to the deep rock and soil layers below with minimal settlement.
Rotary Bored Piling: Used when there are significant obstructions in the ground. Involves installing a temporary casing and removing the arisings before placing a steel reinforcement cage and filling with concrete.
Continuous Flight Auger (CFA) Piling: A versatile method where concrete is pumped into a bored hole, then a steel reinforcement cage is inserted.
Driven and Cast-In-Situ Piles
This method combines driven piles and cast-in-situ concrete. A casing is driven into the ground, and concrete is poured into the casing to form the pile.
Permanent Casing Type: Uses a tubular casing made from reinforced steel, driven into the ground, and filled with concrete.
Franki Type: A temporary casing is used; the casing is withdrawn as dry concrete mix is placed and compacted to form a bulb at the base.
Aggregate Piles
Aggregate piles, or stone columns, use compacted aggregate instead of concrete.
Vibro-Type Aggregate Piles: Create densely compacted columns using a vibrating casing.
Geopier-Type Aggregate Piles: Aggregate is rammed into a casing, creating a dense bulb.
Comparative Analysis of Piling Methods
| Type | Advantages | Disadvantages | Best Suited For |
|---|---|---|---|
| Driven Piles | Increases soil bearing capacity, suitable for deep foundations | Noisy, vibration can affect surrounding structures | Coastal works, sea defenses, jetties |
| Bored Piles | Minimal vibration, effective in obstructions | Requires more equipment, can be slower | Urban areas, sites with obstructions |
| Driven and Cast-In-Situ Piles | Combines benefits of driven and bored piles | Complex installation process | Sites needing high load capacity |
| Aggregate Piles | Environmentally friendly, good for soil improvement | Limited load capacity, not suitable for very deep foundations | Soft ground, marine applications |
Environmental Considerations
Modern piling techniques are evolving to reduce their environmental impact. Sustainable practices include using recycled materials for pile construction and adopting low-impact techniques that minimize disturbance to the surrounding environment.
Recycled Materials: Use of recycled steel and concrete in pile construction.
Low-Impact Techniques: Methods like CFA piling that produce less noise and vibration, reducing impact on nearby structures and communities.
Safety Protocols and Best Practices
Safety is paramount in piling operations. Here are key safety protocols and best practices:
Site Assessment: Conduct thorough site assessments to identify potential hazards.
Training: Ensure all personnel are adequately trained in operating piling equipment.
Protective Gear: Mandatory use of personal protective equipment (PPE) such as helmets, gloves, and safety boots.
Rig Maintenance: Regular maintenance and inspection of piling rigs to prevent equipment failure.
Emergency Procedures: Establish clear emergency procedures and conduct regular drills.
Technological Advances in Piling
Recent advancements in piling technology are making the process more efficient and sustainable:
Carbon Fiber-Reinforced Polymers: These materials offer high strength-to-weight ratios and are corrosion-resistant, extending the lifespan of piles.
Automated Piling Rigs: Automation increases precision and reduces human error, enhancing safety and efficiency.
Digital Tools: Software for planning and monitoring piling projects helps in optimizing design and execution, ensuring better outcomes.
Regulatory and Compliance Information
Compliance with local and international standards is crucial for successful piling operations. Here are some key points:
Regulations: Familiarize with local regulations and obtain necessary permits before starting piling operations.
Standards: Follow industry standards such as those set by the American Society for Testing and Materials (ASTM) and the International Organization for Standardization (ISO).
Inspections: Regular inspections by certified professionals ensure adherence to safety and quality standards.
FAQs and Troubleshooting
What is the main purpose of piling in construction?
Piling transfers loads from a structure into the ground, providing stability and support, especially in weak soil conditions.
What are the types of pile foundations?
The two main types are end bearing piles and friction piles.
How are driven piles different from bored piles?
Driven piles are driven into the ground, increasing soil bearing capacity, while bored piles involve drilling holes and filling them with concrete.
What are aggregate piles used for?
Aggregate piles improve soil bearing capacity using compacted aggregate columns, suitable for marine and other applications.
Why are safe working platforms important in piling?
They ensure the stability and safety of piling rigs during operation, preventing accidents and equipment failure.
Selecting the Best Piling for the Project
STI Group carefully considers the piling needs of each and every civil construction project we work on. Piles, regardless of the material being used, are an essential aspect of the construction process and it is important to consider all of the ramifications of selecting different types of pilings and piling designs. We select the specified piling for all applications per client design, engineering codes and standards. Laying a strong foundation allows the construction project as a whole to operate more safely and efficiently, ultimately helping the facility to reach its full potential of long term success.
References and Further Reading
- Piling Handbook
- ASTM Standards on Piling
- International Society for Soil Mechanics and Geotechnical Engineering
Piling is an essential technique in construction, providing the necessary support for structures in various soil conditions. Understanding the different types of piling and their applications helps ensure that construction projects are safe, efficient, and durable.
