Types of Foundations

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The foundations may be classified in two categories

(i) Shallow Foundations- A foundation is said to be shallow foundation when its depth is equal to or less than its width.

(ii) Deep Foundations- When the depth of the foundation is equal to or greater than its width, then the foundation is termed as deep foundation.

Types of Foundations

Types of Shallow Foundation

(i) Strap Footing- When two or more footings are connected on beam, then it is called strap footing. It may be used where the distance between the columns is so great that a combined trapezoidal footing becomes quite narrow with high bending moments.

(ii) Raft Foundation- A Foundation consists of thick reinforcement concrete slab covering the entire area of the bottom of the structure is known as a raft Foundation.

(iii) Combined footing- The footing which is constructed for two or more columns, is called combined footing. The general shape of combined footing is either rectangular or trapezoidal.

(iv) Spread footing- spread footings are those which spread the superimposed load of the structural over a large area. The spread footing sir following types-

single footing for column, stepped footing for a column, sloped footing for column etc.

Construction Work

Types of deep Foundation

The deep Foundation are mainly three types-

1. Pile Foundation 2. Pier Foundation 3. caisson or well Foundation.

A pile is a long article load transferring member composed of either Timber steel or concrete. Pile Foundation is commonly in construction. A number of piles are driving in the base of the structure in pile Foundations. It is most suitable for bridges.

The pier foundation is suitable for heavy structure like flyover.The caisson is a box of metal,timber or reinforced concrete which is open both top and bottom side.

Classification of piles

1. Classification based on materials and composition

These piles are as follows-

(i) Concrete piles- The concrete piles maybe precast piles and cast in situ piles. The precast concrete piles are generally used for a maximum design load of about 800 kN except for large prestressed piles. The length of precast concrete price varies from 4.5 m to 30 m. The cast in situ concrete piles are casted in position inside the ground and need not to be reinforced in ordinary cases.

(ii) Steel piles- A steel pile may be rolled section, H-section, box pile or circular tube piles. These piles are generally used in retaining walls. The box piles are generally rectangular octagonal or square in shape.

(iii) Timber piles- The timber piles are generally square or circular in cross section and having cast iron shoe at its bottom. The length of the pile should not be more than 20 times of its talk width. The size of square and circular piles maybe between 300 to 500 mm. The timber piles can take a maximum load of 200 KN.

(iv) Composite piles - These piles are made of two portion of two different materials Driven one above. Two common types of composite piles are steel and concrete and timber and concrete.

(v) Screw piles- this file is made of hollow cast iron or steel shaft. The screw pile functions more efficiently in soft clay or loose sand.

(iv) Dise piles- A pile which consist of hollow cast iron pipe with a dise or casing enlarge size at the bottom.

2. Classification based on the function

(i) Bearing piles- The pile do not support the load by themselves, but act as a medium to transmit the load from the foundation to the resisting sub stratum, are known as bearing piles.

(ii) Frictional piles- The pile is driven in such type of soil where the rate of increase strength with depth is very slow. This pile is called frictional piles.

(iii) Compaction Piles- The piles which are driven into granular soil for increasing the bearing capacity of soils, are known as compaction piles.

(iv) Batter piles- The piles which are driven at an inclination to resist inclination force, are called Batter piles.

(v) Fender piles- The piles used to protect water front structures from the abrasion or impact, are called Fender piles.

(vi) Sheet piles- These piles are used to reduce seepage and uplift under hydraulic pressure.

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