This article is about Pile Foundation Construction Installation, pile foundation construction procedure, pile installation methods, pile foundation construction methods, jacking pile installation method, pile driving methods pdf. The process of installing pile foundations is just as important as the design process. There are two primary methods of installing pile foundations: by using a pile hammer or by boring with a mechanical auger. It is crucial to carefully select the installation method and equipment to avoid damaging the piles.
Pile Installation Methods
If a pile hammer is chosen as the installation method, several factors need to be taken into account. Firstly, the size and weight of the pile must be considered. Secondly, the driving resistance that needs to be overcome to achieve the desired depth of penetration must be factored in. Additionally, the available space and headroom on the site, the availability of cranes, and any noise restrictions in the vicinity should also be taken into account.
The selection of appropriate installation methods and equipment is crucial for pile foundation projects to ensure their success. If a pile hammer is chosen, careful consideration should be given to the size and weight of the pile, the driving resistance required to achieve the design penetration, the available space and headroom on the site, the availability of cranes, and any noise restrictions that may be in place. By carefully considering these factors, the pile foundation installation process can be carried out smoothly and with minimal damage to the piles.
Pile Driving Methods (Displacement Piles)
Pile driving is a common method used in construction to provide support for structures and foundations. Different techniques can be employed for this purpose, and one way to categorize them is based on the energy source used to drive the piles into the ground.
The first method is dropping weight, which involves lifting a heavy weight and dropping it onto the pile head repeatedly until the desired depth is reached. Another technique is explosion, which uses controlled blasting to drive the piles into the ground. This method is not commonly used due to safety concerns and the potential for environmental damage.
Vibration is another pile driving method that involves using a vibrating hammer to transmit energy to the pile, causing it to penetrate the soil. This technique is often used in urban areas where noise and vibration levels need to be kept to a minimum.
Jacking, on the other hand, is a method used for micro-piling and involves the use of hydraulic jacks to apply force to the pile. Finally, jetting is a technique that uses high-pressure water jets to loosen the soil and create a hole for the pile to be inserted into. This method is often used in sandy or loose soil conditions.
In summary, pile driving techniques can be classified based on the energy source used, such as dropping weight, explosion, vibration, jacking, and jetting, each with its own advantages and limitations. Here we explain details for two famous methods 1) Drop Hammer Method of Pile Driving. 2) Pile Driving by Vibrating.
1) Drop Hammer Method of Pile Driving.
Drop hammers are a type of hammer used for driving piles into the ground. They are commonly used in situations where it is not economical to bring a steam boiler or compressor to the site for driving a limited number of piles.
There are two main types of drop hammers: single-acting steam or compressed-air hammers, and double-acting pile hammers. Single-acting hammers comprise a cylinder-shaped weight that is raised up by steam or compressed air admitted to the cylinder through a fixed piston rod. The steam is then cut off, causing the cylinder to fall freely onto the pile helmet, either at the top of the stroke or at a lesser height that can be controlled by the operator.
Double-acting pile hammers, on the other hand, can be driven by steam or compressed air and do not require a piling frame. Instead, they can be attached to the top of the pile by leg-guides, with the pile being guided by a timber framework. When used with a pile frame, back guides are bolted to the hammer to engage with leaders, and only short leg-guides are used to prevent the hammer from moving relative to the top of the pile. These hammers are mainly used for driving sheet piles.
2) Pile Driving by Vibrating.
Vibratory hammers are specialized machines used in construction to drive piles into the ground. They are usually powered by electricity or hydraulics, and consist of contra-rotating eccentric masses within a housing that attaches to the pile head. When activated, the machine generates vibrations that are transmitted to the pile. The amplitude of the vibration is strong enough to break down the skin friction on the sides of the pile, allowing it to penetrate the soil.
Vibratory methods are most effective in sandy or gravelly soil types. These types of soils offer less resistance to the pile, allowing it to be driven deeper into the ground with less effort. In contrast, firm to stiff clays or soils containing a significant amount of coarse gravel, cobbles, or boulders are not suitable for vibratory methods.
Another technique that may be used to aid the penetration of piles in sandy or gravelly soils is water jetting. This involves using a high-pressure stream of water to displace soil around the pile and create space for it to be driven deeper into the ground. However, water jetting has very limited effectiveness in soils that contain a significant amount of coarse gravel, cobbles, or boulders, or in firm to stiff clays.
Boring Methods (Non-Displacement Piles)
Boring methods refer to the technique of creating piles by drilling or boring a hole into the ground and filling it with concrete or another material to create a stable foundation. Non-displacement piles are those that do not displace the surrounding soil as they are installed. Here are some common boring methods for non-displacement piles:
- Auger Piles: In this method, a continuous flight auger is used to drill a hole into the ground, which is then filled with concrete or grout. The auger is withdrawn while the concrete is pumped in, ensuring that the surrounding soil is not disturbed.
- Driven Cast-In-Place (DCIP) Piles: In this method, a steel casing is driven into the ground to create a hole, and then the casing is filled with concrete or grout. The casing is left in place to provide reinforcement for the pile.
- Rotary Bored Piles: In this method, a drill bit is used to create a hole in the ground, and then the hole is filled with concrete or grout. As the hole is drilled, a temporary casing is used to support the sides of the hole until the concrete is poured.
- Continuous Flight Auger (CFA) Piles: In this method, a hollow auger is used to drill a hole into the ground, and then concrete or grout is pumped through the hollow center of the auger while it is withdrawn. The auger is rotated continuously as the hole is drilled and filled, ensuring that the surrounding soil is not disturbed.
Non-displacement boring methods are commonly used in urban areas where there is limited space and adjacent structures may be sensitive to vibrations or ground movements. They are also useful in areas with difficult soil conditions, such as areas with high groundwater levels or soil that is prone to collapse. Following we explain famous methods only for students and professionals.
Continuous Flight Auger (CFA)
The process of constructing a pile involves the use of a mobile base carrier equipped with a hollow-stemmed flight auger, which is rotated into the ground to the desired depth. Concrete is then poured through the flight auger as it is withdrawn from the ground to form the pile. The top mounted rotary hydraulic motor attached to the mast rotates the auger into the ground.
Once the desired depth is reached, highly workable concrete is pumped through the hollow stem of the auger, which leads to the detachment of the protective cap at the base of the central tube. The auger is then rotated in the same direction as during the boring stage, and the spoil is expelled vertically as the auger is withdrawn. The pile is formed by filling it with concrete.
For the successful operation of the rotary auger, it is crucial to match the rotation of the auger with the flow of concrete to prevent the collapse of the sides of the hole above the concrete on the lower flight of the auger, which may result in voids being filled with soil in the concrete. This method is highly effective on soft ground and can install a variety of bored piles with varying diameters that can penetrate different soil conditions. However, it is important to note that the soil must be self-supporting and reasonably free of tree roots, cobbles, and boulders for the rotary auger to work correctly.
During the operation of the rotary auger, minimal soil is brought upwards by the auger, which helps maintain lateral stresses in the soil and minimize voiding or excessive loosening of the soil. Nevertheless, if the rotation of the auger and the advance of the auger are not matched, the soil may be removed during drilling, which could cause the side of the hole to collapse.
Underreaming
Auger bored piles have a unique feature that allows for the exploitation of the bearing capacity of suitable strata by providing an enlarged base. This technique can only be used in soil that is capable of standing open unsupported. Stiff and hard clays, such as the London clay, are ideal for this purpose. To create the enlarged base, an underreaming tool is fitted inside the straight section of a pile shaft while in its closed position. The tool is then expanded at the bottom of the pile to produce the underream as shown in Figure 3.
It is important to inspect the shaft and the underream of the pile before concrete is casted. To do this, a man carrying cage is lowered to the bottom of the pile. This inspection ensures that everything is in order and that the pile is capable of providing the necessary support. By using this technique, the bearing capacity of the pile is significantly increased, which makes it a popular choice in the construction industry. However, it is important to note that this technique can only be used in suitable soil conditions, as the soil must be able to stand open unsupported.
Figure 3 displays three different pieces of drilling equipment commonly used in the field of geotechnical engineering. The first piece of equipment, shown in part (a), is hydraulic rotary drilling equipment. This type of equipment is used to drill boreholes into the ground and is powered by hydraulic pressure.
Part (b) of the figure shows a Continuous Flight Auger, which is another type of drilling equipment. This tool is used to bore holes in the ground by screwing into the soil and then removing the soil in a continuous flight. The flight auger is a hollow tube with a cutting edge on the bottom and a central shaft that rotates and drives the auger into the soil.
The third piece of equipment shown in Figure 3, part (c), is an underreaming tool in its open position. This tool is used to enlarge the diameter of a borehole after it has been drilled. The underreamer consists of several arms that can be extended and retracted by a hydraulic mechanism. When the arms are extended, they create a wider diameter hole than the original borehole.
Pile Driving Methods
The pile method of underpinning is a construction technique used to stabilize and strengthen the foundation of an existing building or structure that has settled or shifted due to unstable soil conditions or other factors.
In this method, piles (long, slender columns made of steel, concrete, or wood) are driven vertically into the ground at regular intervals around the perimeter of the structure, usually on the outside of the existing foundation. The piles are driven deep enough to reach a stable soil layer or bedrock, and they provide additional support and stability to the foundation by transferring the weight of the structure to the stronger ground below.
Once the piles are in place, a steel needle or pin is inserted through the existing foundation wall and connected to the pile cap, which is a horizontal beam that supports the weight of the structure. The needle or pin helps distribute the load from the foundation and walls evenly across the piles, ensuring that the structure is properly supported and stabilized.
The pile method of underpinning is often used in situations where the existing foundation is too weak to support the weight of the structure or where the soil conditions are not suitable for traditional foundation construction. It can be a complex and expensive process, but it is often the most effective way to prevent further damage to the building and ensure its long-term stability.
FAQs about Pile Foundation Installation
1. Is a new technique used for the installation of pile?
The use of micropiles in foundation construction is not a new technique. However, the specific method you described, using a nozzle on an excavator to install the micropiles directly in the knocked-out wells, may be a relatively new development.
Micropiles are typically small-diameter piles that are drilled and grouted into the ground. They are often used in situations where traditional pile installation methods are not feasible, such as in areas with limited access or low headroom.
Using an excavator with a nozzle to install micropiles could potentially offer some advantages over traditional drilling methods. For example, it may be faster and more efficient, and could potentially reduce the amount of material that needs to be excavated and removed from the site. However, the effectiveness and safety of this method would depend on a variety of factors, including soil conditions, the size and type of the excavator and nozzle, and the skill and experience of the operator.
2. What is pile method of underpinning?
The pile method of underpinning is a construction technique used to stabilize and strengthen the foundation of an existing building or structure that has settled or shifted due to unstable soil conditions or other factors.
In this method, piles (long, slender columns made of steel, concrete, or wood) are driven vertically into the ground at regular intervals around the perimeter of the structure, usually on the outside of the existing foundation. The piles are driven deep enough to reach a stable soil layer or bedrock, and they provide additional support and stability to the foundation by transferring the weight of the structure to the stronger ground below.
Once the piles are in place, a steel needle or pin is inserted through the existing foundation wall and connected to the pile cap, which is a horizontal beam that supports the weight of the structure. The needle or pin helps distribute the load from the foundation and walls evenly across the piles, ensuring that the structure is properly supported and stabilized.
The pile method of underpinning is often used in situations where the existing foundation is too weak to support the weight of the structure or where the soil conditions are not suitable for traditional foundation construction. It can be a complex and expensive process, but it is often the most effective way to prevent further damage to the building and ensure its long-term stability.