Building foundations are usually too frail to carry the weight of a superstructure on their own. There are various methods to lower the intensity of loads and fortify the soil. One of the most widely used deep foundation techniques worldwide is piling. Modern piling solutions are very advantageous to the construction project because they are the most efficient method for deep foundation.
How Are Piles Utilised in Construction Techniques?
In order to convey and transfer loads to the soil, piles are driven or drilled through the ground along a specific length of the land. In general, piles are typically used when the soil’s load capacity is insufficient to support the structural weight of the building. Through piling, the loads are transferred by the piles to a depth of solid earth. For deep foundation projects, piling is utilised to ensure that the building structure is supported both above and below ground. Piling rigs are simply inserted into the earth up to bedrock. The weight of what is above ground can then be safely and firmly supported by the pile. In general, additional attachments like conical tips are frequently added to the pile in order to drive it more effectively. According to the design requirements of the contractor in charge of the project, these attachments are welded to the end of the pile.
The Birth of Piling
Pile construction has a long history. It started with the construction of foundations on flimsy peat soils next to rivers in prehistoric times. In order to ensure adequate protection of the land as well as the supply of water, many villages and cities were situated close to lakes and rivers. As a result, timber piles that were either driven into the ground manually or fastened into holes that were filled with stones and sand were used to strengthen the poor bearing ground. There were numerous instances in Britain where timber piles were used. Throughout history, piling has been mentioned in numerous books of various genres. Swiss settlers and lake dwellers used piling years ago and built structures on piled foundations to elevate their homes. The constant demand for buying land has compelled governments and development organisations to use property with poor soil qualities. Piling is essential to the modern construction sectors.
What Kinds of Pilings Are There?
Building engineers must evaluate the parameters of their construction site, including the soil, climate, and other elements, before deciding between piling types. In order to comprehend the scope of their infrastructure project, they will also need to engage with architects. With the use of this knowledge, they can plan for building solutions and select the ideal piling type. Friction piles and end-bearing piles are the two primary forms of piling that are used in construction.
The way friction piles withstand the loads placed on buildings is by growing their capacity to support loads through skin shear stresses. Skin friction develops when the pile surface and the surrounding dirt adhere to one another or rub against one another. All of the pile surfaces efficiently resist the load due to friction or adhesion, which also lowers the bulb pressure on the pile surface. When using friction piles, a pressure zone of cylindrical shape forms around the pile surface.
End Bearing Piles
End bearing piles are used to transmit superstructure load from a weak stratum, (such as rock or extremely dense sand and gravel) to a strong stratum with a higher bearing capacity. The resistance of the dense soil layer at the pile’s end serves as the primary indicator of their load-bearing capabilities. At least three times the pile’s diameter must be inserted from the pile’s end into the hard strata. This action is thought to fully exploit the layer’s ultimate strength beneath the pile tip. End-bearing piles can be constructed using prefabricated piles.
Pile Construction Techniques
A broad variety of pile types are available for applications with diverse soil types and structural requirements. Pile techniques can be determined by their fundamental design purpose.
- Driven Piles
- Aggregate Piles
- Bore Piles
- Screw Piles
Displacement piles, often referred to as driven piles, are a popular kind of deep foundation that supports structures by transferring their weight to strata of rock or soil that are strong enough to hold the weight and have the suitable settlement properties. Driven piles are frequently employed as the most economical deep foundation method in order to support buildings, walls, towers, and bridges. They can also be used for projects like cofferdams and anchorage structures. Driven piles are used for retaining walls, bulkheads, and embankments.
Replacement piles, also known as bore piles, are widely used for building foundations. They can support structures by shifting their weight to the soil that is suited for settling and have a sufficient bearing capacity. Bore heaps are piles where the removal of debris creates a hole. Then reinforced concrete is poured into that hole. In contrast to displacement piles, which are driven or screwed into the ground to push the soil away, replacement piles are used to replenish spoil. Bore piles are typically used in cohesive subsoils in order to create friction piles and build pile foundations adjacent to existing structures. There are two frequently utilised kinds of bored pile foundations known as rotary bore and CFA piling.
Piling Fitted with a Rotary Bore
Rotary bore piling is utilised by construction companies when there are severe impediments on the earth. This piling rig installs a temporary shell to act as support for the structure. A revolving cage is inserted into the ground to reinforce unstable soil, and the pile is then extracted using an auger unit. After the bore has been carefully cleaned to the proper depth and the pile has been inserted, the casing is removed, leaving the finished pile behind. Rotary Bore Piles are used to fortify the ground. That way, the ground can hold the load of the structure that will be erected on top of it. In this method, drilling is done to the designated depth using a crane-mounted or track-mounted hydraulic drill.
Piling Fitted with Continuous Flight Auger
CFA piling is the most adaptable, efficient, and widely used kind of pile foundation since it doesn’t require the use of temporary casing. It is also one of the most quietest forms of piling. The Continuous Flight Auger is an auger-bored replacement pile that includes soil extraction and pressure-pumped concrete. A helical screw with a hollow stem that has been bored into the earth to the desired depth is used to build the pile. Concrete pouring is accomplished by injecting fluid concrete down the auger’s hollow stem and into the pile bore. The piles are usually raised to the surface during the drilling and concreting phases.
In screw pile, a helix is present close to the pile toe, which enables the piles to be pushed into the earth. Depending on the purpose and the ground circumstances, a screw pile may contain more than one helix, also known as a screw. If a heavier load is necessary or soft ground is encountered, more helices are typically supplied. Large torques are applied by strong hydraulic motors in order to insert a screw pile further into the soil. A lot of thought must be given while designing the interaction between the pile and the structure. The building and the surface that the piles are drilled into are taken into account while designing the connection. Casting the screwpile’s head into the concrete foundations of the building is the most typical way to attach a screw pile to a building’s foundation. Fixing is achieved by casting steel reinforcing bars into the piles, some of which extend into the building’s footing.
Aggregate piles are basically columns of compacted stone. They are erected in groups inside the poor soil in order to improve bearing pressure and reduce settlement under structural footings. Bibro stone columns or rammed piles may both be referred to as aggregate piles. Due to the materials used in aggregate piles the speed of construction is a lot faster. Aggregate piles are frequently the most affordable alternative for building on soft soils. To force it out of the ground in order to form a dense bulb usually aggregate is shoved into a casing.
There are numerous techniques for installing piles, and each is chosen according to the situation of the soil. The following are some of the many variables that may affect the method of installation:
- Your excavation’s depth
- The materials used to create your piles
- How steeply you’re driving your piles
- There are environmental problems that could affect the piling installation.
The process of installing displacement pilings involves driving piles into the earth without removing any dirt or other materials. In order to lower the underlying soil resistance and enable the pile to slide into the earth, driven piles can be hammered, jacked, or vibrated into the earth. There are various tools that are used for piling, such as a percussive hammer, hydraulic motor, or rams.
Guidelines for Working Platforms (FPS)
Depending on the type of piles and their size, a variety of piling rigs are produced. Rigs must be manoeuvred and positioned precisely for each pile location. The piling platform is the location where the rigs are placed. In order to create platforms, a layer of filling is often compacted to a predetermined depth. For brownfield developments, the required fill might be delivered to the site. Demolition debris from the site could also be used to create a filling. To maintain the safety and reliability of the rig, the piling platform is necessary to disperse the weight from the tracks. A qualified engineer should properly design the working platforms by utilising the soil data. Platforms must be correctly built, and the contractor must do routine inspections and maintenance. According to the Federation of Piling Specialists, piling platforms are involved in one-third of all dangerous incidents on construction sites. Every dangerous incident involving the piling platform is said to be a possible fatality. The piling platform must be designed and built by the primary contractor for the project, who frequently outsources the design work to a licenced engineer. The Principal Contractor is needed to sign the certificate indicating that the platform has been designed correctly. The contractor makes sure that everything is constructed in line with the layout and that it will be routinely inspected and maintained. The Federation of Piling Specialists maintains a certification system for the piling platforms.