mat foundation
A foundation consisting of a very thick continuous concrete slab.
In locations where the soil is weak and the bedrock is extremely deep, floating or compensated mat foundations are sometimes utilized. For this type of foundation, the amount of soil removed and the resulting uplift (on the foundation) caused by groundwater is equalized by the downward forces of the building and foundation. Yet another variation of the mat foundation is to use it in combination with caissons or piles.