Footing and foundations

The more common types of foundation structure are: isolated spread footings (one to each column); combined footings (one to two columns); and mat, or raft, foundations (all columns resting upon a heavy slab).

Spread footings may be used under either walls or columns and may be of timber, steel, plain masonry, or reinforced con­crete.

Wall Footings. —The footings in this case act as a cantilever beam with the load acting upward and the support at the middle.

Continuous Footings under Columns. —When footings are built continuously under columns, the footing takes on the nature of a beam carrying concentrated loads at column points acting downwards and distributed load acting upward.

Floating Foundations is a term applied to practically monolithic footings built under an entire structure which have been used widely for construction on soils of more or less plas­tic nature. Pile foundations are used in the areas where the other kinds of foundations cannot be constructed. By driving bearing piles, the support of structure is transferred in an irregular manner to the earth stratum.

Timber piles. —Timber piles have been used almost exclusively in the past in foundation work; but with the growing scarcity of timber and the development of concrete, reinforced concrete piles are coming to be extensively used.

Pile driving. —Piles may be driven by means of a pile driver or a water jet. Pile drivers may be classed as drop ham­mers and steam hammers.

Caissons. —The word " caisson" is derived from the French word meaning " case". As applied to engineering construction, a caisson may be defined as a large watertight box used to exclude water or other fluid and semifluid material during excavating of foundations and the construction of substructures and ultimately becoming an integral part of the structure.

Tasks after reading:

Define which of these statements contain the main idea of the text. Prove your opinion

1. The more common types of foundation structure are spread, combined footings and raft foundation.

2. Footings and foundations may rest either on the bearing soil or on the heads of piling.

Put these sentences in order according to the context. Add some more necessary sentences

1. The support of structure is transferd in an irregular manner to the earth surface. 2. It may be defined as a large watertight box.3. They act as a cantilever beam.4. They may be driven by means of a pile driver or water jet.