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This definition has limitation when its width becomes larger. A sensible definition can be used
-its depth less than breadth
-its depth less than3 meters.
Deep foundation generally transmits loads of structure to considerably greater depth through lower portion of superstructure. The usual deep foundation are
-pile
-pier
-caissons etc.
Shallow foundations, often called footings, are usually embedded about a metre or so into soil. One common type is the spread footing which consists of strips or pads of concrete (or other materials) which extend below the frost line and transfer the weight from walls and columns to the soil or bedrock.
Another common type of shallow foundation is the slab-on-grade foundation where the weight of the building is transferred to the soil through a concrete slab placed at the surface. Slab-on-grade foundations can be reinforced mat slabs, which range from25 cm to several meters thick, depending on the size of the building, or post-tensioned slabs, which are typically at least20 cm for houses, and thicker for heavier structures.
A deep foundation is used to transfer the load of a structure down through the upper weak layer of topsoil to the stronger layer of subsoil below. There are different types of deep footings including impact driven piles, drilled shafts, caissons, helical piles, geo-piers and earth stabilized columns. The naming conventions for different types of footings vary between different engineers. Historically, piles were wood, later steel, reinforced concrete, and pre-tensioned concrete.
Shallow foundation:
A type of foundation that is used when the earth directly beneath a structure has sufficient bearing capacity to sustain the loads from the structure .
1. Light, flexible structure: older residential construction, residential construction which include a basement, and in many commercial structures,
2. Nice soil condition: hard, uniform soil.
3. Cheaper than deep foundation
4. Easier construction
5. Typically types: spreading footing foundation, slab-on-grade foundation, pad foundation, strip foundation, and raft foundation.
Spreading footing foundation: controlled by several factors: lateral and vertical capacity, penetration through near surface layers likely to change volume due to frost heave or shrink-swell.
Mat-slab foundation: the distribution of loads in a mat slab helps reduce differential settlement due to the non-uniform building loads . But the characteristics of the deep foundations are as follo A type of foundation that is used when the soil near the ground surface is weak
1. Heavy, rigid structure: other uncommon building, such as large bridge, tower, and the empire state building.
2. Poor soil condition: liquefaction, soft clay and sands.
3. Typically more expansive
4. More complex to construct and more time than shallow foundation.
5. Typically types: battered piles, bearing piles, caissons, and friction piles.
Friction piles: Friction piles obtain a greater part of their carrying capacity by skin friction or adhesion. This tends to occur when piles do not reach an impenetrable stratum but are driven for some distance into a penetrable soil. Their carrying capacity is derived partly from end bearing and partly from skin friction between the embedded surface of the soil and the surrounding soil.
End bearing piles: End bearing piles are those which terminate in hard, relatively impenetrable material such as rock or very dense sand and gravel. They derive most of their carrying capacity from the resistance of the stratum at the toe of the pile
