Stiff Foundation Mat

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.

Stiff foundation mat.

Ive always thought of strip footing under the wall whoes 45 degree disperse load line doesnt pass thru the bootom as a stiff foundation. Mat foundation is also known as the raft foundation. 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. A stiff foundation mat below is a good type of shallow foundation which can transfer loads from locally liquefied zones to adjacent stronger ground.

Loads on raft or mat foundation. A mat foundation is a thick reinforced concrete slab supporting arrangements of columns or walls in a row or rows and transmitting the loads to the soil. Buried utilities such as sewage and water pipes should have ductile connections to the structure to accommodate the large movements and settlements that can occur due to liquefaction. A mat foundation is in essence a stiff slab that acts as a single foundation element that covers the entire plan area of the structure.

As any shallow foundation a mat foundation has to be checked against bearing capacity failure and excessive total average settlement. It is common to use mat foundation or deep basements. If i imagine this same strip footing placed under 3 columns spaced few meters away and acting as 3 point loads i would say that the foundation would behave a flexible since it will start bending.