Different types of pile foundations are used in construction projects where structures cannot be built on a flat foundation.
A pile is a type of foundation driven into hard layers of earth or rock. The settlement of pile foundations is very low compared to shallow foundations. However, quality control for pile foundations is very difficult compared to shallow foundations because we cannot see anything visually.
Why pour foundations?
There are essentially a few reasons to choose piles as your foundation type.
- Weak soil conditions
If soil conditions are too weak, the bearing capacity of the soil will be too low. As a result, the area of the shallow foundation increases and the settlement of the foundation also increases.
Additionally, building a foundation is not an option in compressible soils such as peat or similar natural soils.
In such situations, we choose this Deep foundation as an option for storing the structure. As there are different types of deep foundations, we can choose the most suitable and economical type of pile foundation.
- High column load or structural weight
The first option we consider for the foundation is a shallow foundation, as this is generally the most economical solution.
However, it is not always possible to rely on shallow foundations.
If the column loads are high, the foundation area must be increased. In these cases, it may be necessary to build a slab foundation. Because the allowable bearing capacity of the soil is limited, not all structures can be built on a slab foundation.
In general, buildings of around ten stories can be built on slab foundations if the soil has the necessary bearing capacity. The costs of constructing a pile and slab foundation can be at the same level. Most of the time, the slab foundation cost can be less.
Taking all aspects into consideration, we can choose the most suitable Foundation, Donation Type. Most tall buildings have very high axial loads. This is why pile foundations are built.
There are different classifications for pile foundations.
Classification of piles by support mechanism
The support arrangement method is considered here to distinguish types of deep foundations. There are essentially two methods we can use to sort stacks.
- Final stakes
Most of the types of piles we build are end support piles.
The tip of the pile counteracts the vertical movement of the pile. The penetration resistance of the pile tip is considered as final support.
The pile rests on the ground, weathered rock or fresh rock. The ultimate load capacity varies depending on the condition of the support material and the foot area.
Rock creates the highest supporting pressure while soil creates the lowest supporting pressure.
The final support of the pile can be calculated as follows:
F b =f b A b
F b – Load capacity of the pile tips. An appropriate safety factor must be applied.
F b – the maximum allowable load capacity cannot be determined by laboratory tests of the soil or rock on which the pile rests.
A b – Velvet toe area
- Friction piles
Most types of driven piles are friction piles.
The friction between the soil and the pile creates resistance to penetration of the pile. This is called Skin Friction .
The pile surface, ground cover, soil type, etc. affect the surface friction of the pile.
When discussing pile skin friction, we need to consider three areas.
Ground surface friction – whether the post is closed or not, we can calculate the skin friction for it pile construction . This is called positive skin friction to counteract the downward movement of the pile.
Negative skin friction – This is a type of skin friction that acts in the opposite direction. Reduces the geotechnical load capacity of the pile. When weak, compressible soils are present, as they settle over time, a downward resisting force is created on the pile. This reduces the load bearing capacity of the pile.
Rock surface friction – If the pile is anchored in the rock, skin friction occurs along this length. The skin friction of the rock is dominant and sometimes sufficient to support the loads of the structure.
The surface friction of the pile is calculated as follows:
F S =f S A S
F S – permitted surface friction of the soil/rock
F S – permitted skin friction stress (from recommendations)
A S – Pile surface of the relevant section
Classification of piles by construction materials
There are many types of pile foundations in this category. Let's discuss each battery type in detail.
- wooden posts
One of the oldest types of poles is the wooden pole.
They were built in ancient times. This involved not only building on land, but also building a structure over water using wooden piles.
Resistant types of wood Wood decay Due to environmental conditions, construction uses materials that have high resistance to support the load of the structure.
- Concrete piles
One of the most commonly used types of pile foundations is concrete piles.
Compared to other types of piles, it has a greater load capacity because concrete has a very high compressive strength.
Generally, the concrete pile is designed as a friction pile or end bearing pile. The precast pile is the friction pile and the cast-in-place bored piles are classified as end bearing piles.
Furthermore, prefabricated piles are also known as driven piles because they rest in the ground and are subsequently driven into a hard layer of soil. Mechanical methods or vibrating hammers are used to drive the piles.
On the other hand, the conventional method is used to cast concrete bored piles in situ. Bored pile construction includes soil and rock excavation, cleaning, concreting and quality control testing.
- Sheet piles (metal piles)
Sheet piles are not the type of pile foundation used for load-bearing purposes like concrete piles.
They are mainly used to support lateral loads. In retaining construction, sheet piles are mainly used to resist earth movements, etc.
The nature of the pile increases its transverse stiffness. Furthermore, they are connected to each other by mutual locking.
Sheet piles are generally driven using vibratory hammers. Some machines produce less vibration. If we use them in a critical location, ground vibrations must be minimal.
- steel piles
Steel piles are only used on special occasions and are not commonly used due to corrosion issues.
If the pile corrodes, it will affect structural stability. It is common practice to check soil and groundwater conditions for harmful chemicals that can cause corrosion.
This reduces the useful life of the structure. Therefore, the construction of metal piles must be carried out with great care.
- Composite piles
Generally, composite piles are a combination of steel and concrete.
If we build a steel pile covered with concrete, it can also be considered a composite pile. However, when constructing the steel pile, we use a concrete cover around the pile to protect it from durability issues.
The steel pile is equipped with a reinforcing mesh inside the steel casing to increase its load capacity. This type of battery is also called a microcell.
- Secant cuttings
For deep underground excavations, secant piles are mainly used as foundations.
When it is necessary to build a deep basement without affecting the surrounding structures, we mainly use this type of pile foundation.
When the water table drops, it has a direct impact on structures built on shallow foundations. Furthermore, continuous dewatering in a deep excavation without affecting the structure is almost impossible.
There are two types of in situ concrete piles in the form of secant piles. Male cuttings and female cuttings. First, the pile is concreted without reinforcement at a certain distance. Then the reinforced cage pile is concreted with some overlap between the female piles. This prevents water from entering the excavation pit.
Secant piles are a type of retaining wall. Therefore, they are generally embedded in the rock to absorb the loads that occur.
