What is foundation in construction work:-
Foundation of structure
Foundation is the lowest structure in any building, it will transfer the load from the superstructure to the soil. (Substructure) But because of the small perimeter the pillar punch (setter or goes inside the soil) Therefore, foundation is provided only to increase the circumference so that the load can be distributed over the larger area. Foundations are generally classified as two categories shallow foundations and deep foundations. ... Once the foundation is packed tightly, or the hardener has dried, we can begin to build the building superstructure
Two types of foundation:-
1.Deep foundation.
2.shallow foundation.
Deep foundation:-
Deep foundation
Deep foundation :- A deep foundation is a type of foundation that is placed at a greater depth below the surface of the ground and transfers the structure load to the earth at depth
The structuring process of a deep foundation is more complex and more expensive than that of a shallow foundation.
If the depth of the footing is equal to or more than the width of the footing, it is known as deep foundation. Deep foundations are used where the bearing capacity of the soil is very
low
Types of deep foundation:-
pile foundation
casson
Cylinder
basement
hollow box foundation (buoyancy raft)
shaft foundation
1. pile foundation:- Pile foundations are constructed by driving prefabricated units into the required founder level or by drilling, driving tubes filled with concrete, to the desired depth. Tubes can be filled with concrete in a variety of ways – they can be filled during or before evacuation, or by drilling unlined, partially lined, or fully lined boreholes before being filled with concrete. can be filled through
Pile foundation
These foundations are used when soil, construction or economic conditions make it necessary to transport the load of structures to levels beyond the reach of shallow foundations. In addition to supporting structures, piles can be used to help resist uplift, overturn and lateral forces. They are used as foundations for waterfront installations, bridges and buildings.
2. casson:- These are hollow substructures that can be constructed near or on the ground surface and submerged as a unit to the desired level. They have heavy load bearing capacity and are commonly used for bridges.
3. Cylinder :- These are small caissons containing only one cell.
4. basement foundation:- These hollow substructures provide storage or work space below ground level. They are built in open excavation. Functional requirements govern their structural design.
5. buoyancy raft:- Buoyant rafts, also known as hollow box foundations, are designed to form a semi-enthusiastic or buoyant structure beneath which the loading on the soil is reduced to the low intensity required. They can be constructed in open excavations or can be submerged like caissons.
Hoist rafts are more expensive than traditional forms of foundation. For this reason, their use is usually limited to sites on silts, soft sands and other alluvial deposits that are too deep, or where loads can be kept concentric. Plans requiring underground tanks or where it is economical to incorporate deep basements into the design are common.
6. shaft foundation:- These foundations are constructed by drilling a cylindrical hole within a deep excavation and later placing a concrete or other prefabricated load-bearing unit in it. Their length and shape can be easily tailored. Drilled shafts can be constructed near existing structures and under low overhead conditions, making them suitable for use in many seismic retrofit projects. However, they can be difficult to establish under certain conditions such as boulder soil, soft soil, loose sand and underwater sand.
Shallow foundation:-
A shallow foundation is a type of building foundation that transfers structural loads to the earth very close to the surface, rather than a subsurface layer or a range of depths, as a deep foundation does. Traditionally, a shallow foundation is considered to be one when the width of the entire foundation is greater than its depth. [1] Compared to deep foundations, shallow foundations are less technical, thus they are more economical and most widely used for relatively light structures
Types of shallow foundation:-
1. wall footing:- Also called strip footing, this footing is a continuous bar that supports structural and non-structural load bearing walls. Found directly under a wall, its width is usually 2-3 times wider than the wall above it.
2. isolated footing:- Also called single-column footing, it is a square, rectangular, or circular slab that supports structural members individually. Normally, each of its pillars gets its own base to transmit and distribute the load of the structure towards the soil below. Sometimes, an isolated footing may be placed on a slope or base to spread more load. This type of footing is used when the structural load is relatively low, the columns are widely spaced, and the soil carrying capacity is sufficient at shallow depths.
Categories of Isolated footing
3. joint footing:- When more than one column share the same footing, it is called combined footing. It is used when the spacing of the columns is very limited, if separate footings are used, they will overlap each other. Also, when the property line loads individual footings eccentrically, combined footings are preferred.
When the load between the pillars is equal, the joint base may be rectangular. Conversely, when the load between the pillars is unequal, the joint base must be trapezoidal.
4. Strap footing:- Strap footing occurs when individual columns are attached to each other using a strap beam. Strap footing has the same general purpose as combined footing, where the spacing is probably limited and/or the columns are adjacent to property lines.
5. Matte Foundation :- Also called a raft foundation, it is a single continuous slab that covers the entirety of the base of a building. The mat foundation supports all the loads of the structure and transmits them evenly to the ground. Soil situation may Interrupt other footings from being used. Since this type of foundation distributes the load coming from the building more evenly over a fairly large area, it is suited when individual feet are inefficient due to the low bearing capacity of the soil
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