Mat Foundation Settlement

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 settlement.

The mat foundation can be analysed as either rigid or flexible depending on the size and thickness of the mat and the strength of the subgrade. If settlements beneath the mat foundation are more than the rigidity of the structure will permit a redistribution of loads takes place that will. It is common to use mat foundation or deep basements to transfer the column loads to the underlying soil as well as provide floor slab for the basement. 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.

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. Mat foundations are popular in areas where basements are common. Thus an allowable maximum settlement of 50 mm is usually specified for raft foundations. Whereas for footings only 25 mm is specified for the same allowable differential settlement of 18 mm 3 4 inches for both cases.

This foundation supports the entire building loads and safely transfer it to the ground. The designer can analyse a mat foundation of any size including up to 32 columns placed anywhere on the foundation. 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. It is used to reduce differential settlement of buildings.

The settlement of the mat foundation will be within limits that the structure can safely tolerate as a flexible structure. This spreadsheet can be used to complete the design of mat foundations. Mat foundations are sometimes preferred for soils that have low load bearing capacities but that will have to support high column or wall loads. Common types of mat foundation.

Raft or mat foundation is used when the soil layer is unstable. The columns can be subjected to axial horizontal and moment forces. Mat foundation is specified to bridge over pockets of weak spots in moderately weak soil. The settlement tends to be controlled via the following.

Under some conditions spread footings would have to cover more than half the building area and mat foundations might be more economical. 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.