Foundation | Shallow Foundation
According to Terzaghi, the foundation is shallow if its depth is equal to or less than its width.
Types of shallow foundation
- Spread footing
- Combined footing
- Strap Footing
- Mat Foundation
- Raft Foundation
- Grillage Foundation
- Spread footings are these which spread that super-imposed load of wall or column over a larger area.Spread footing helps either column about the wall.
- Each spread footing that holds two or more columns is termed combined footing.
These combined footing someone of the following kinds.
- Rectangular combined footing:– The combined footings will be provided in rectangular shape if columns carry equal loads. The design of rectangular combined footing should be done in such a way that the centre of gravity of the column coincides with the centroid of the footing area.
- Trapezoidal combined footing:- If columns carry unequal loads the footing is of trapezoidal shape are provided.
- Combined column-wall footing: It may be required to provide a combined footing for columns and walls. A such combined footing is shown in Fig.
- If an Independent footing of two columns is connected by a beam, it is called a strap footing.
- Each strap footing may be applied where the distance between this column is so great that the trapezoidal footing becomes very narrow.
- The strap gives not remain in contact with the soil and also does not transfer each pressure to the soil.
- A raft foundation equals a combined footing that treats the entire area beneath a structure and also supports everything the walls and columns.
- They are used in areas where the soil masses contain compressible lenses or the soil is sufficiently erratic so that differential settlement would be difficult to control.
- Raft a foundation may be divided into three types based on their design and construction.
- Solid slab system
- Beam slab system
- Cellular system
- All three types are basically the same, consisting of a large, generally unbroken area of slab covering the whole or large part of a structure.
- It is a special type of isolated footing generally provided for heavily loaded steel columns and used in that locations where the bearing capacity of the soil is poor.
- The pitch of such a foundation is limited to 1 to 2 m.
- The load of steel, a column is distributed over a very large area utilizing two or more tiers of steel joints.
- Each layer is laid at a right angle to the layer below it.
Last updated on Wednesday - June 7th, 2023