Mat Foundation Settlement

The settlement of the mat foundation will be within limits that the structure can safely tolerate as a flexible structure.

Mat foundation settlement.

A mat foundation is used when the subsoil is weak and column loads are so heavy that the conventional spread footings cover more than 50 of the building area. It is used to reduce differential settlement of buildings. Mat foundations are sometimes preferred for soils that have low load bearing capacities but that will have to support high column or wall loads. The columns can be subjected to axial horizontal and moment forces.

This spreadsheet can be used to complete the design of mat foundations. Use of a larger foundation to produce lower soil contact pressures. It is a continuous thick concrete slab on the soil that extends the entire footprint of the building and increases the soil bearing capacity power. Mat foundations are popular in areas where basements are common.

Under some conditions spread footings would have to cover more than half the building area and mat foundations might be more economical. Mat foundations are commonly used where settlements may be a problem for example where a site contains erratic deposits or lenses of compressible materials suspended boulders etc. Mat foundation is also used for low bearing capacity soil in order to spread the load of a building and hence construct a stable foundation. Mat foundation is also known as the raft foundation.

The designer can analyse a mat foundation of any size including up to 32 columns placed anywhere on the foundation. Raft or mat foundation is used when the soil layer is unstable. Compared to spread footings the differential settlement in a mat foundation is much more reduced as the mat bridges over the loose pockets and lenses of a soil deposit. If settlements beneath the mat foundation are more than the rigidity of the structure will permit a redistribution of loads takes place that will.

This foundation supports the entire building loads and safely transfer it to the ground. The settlement tends to be controlled via the following. Whereas for footings only 25 mm is specified for the same allowable differential settlement of 18 mm 3 4 inches for both cases. Mat foundation is specified to bridge over pockets of weak spots in moderately weak soil.

Common types of mat foundation. It has been found that for the same loading intensity and soil condition the differential settlement in a mat foundation is about 1 2 than that of a spread foundation.