This type of mat is used when the columns and walls are uniformly spaced at small intervals and the subjected loads are relatively small. This is the simplest form of raft foundation. Rigid Frame Mat or Cellular Raft Foundationĭifferent types of mat foundation are briefly discussed below.Several types of Raft foundation may be used depending on the condition of soil and the load imposed on the foundation.įollowings are the different types of raft foundation used in construction: Any other type of footing cannot be used advantageously.When soil strata are unpredictable and contain pockets of compressible soil.There is a possibility of differential settlement in case individual footing is used.The columns or walls are placed so closely that the individual footings would overlap.Individual or any other foundation area would approximately cover 50% of the total ground area beneath the structure.Load of the structure has to be distributed over a large area.When to Choose Raft Foundationįor foundation design, one of the most important aspects is choosing the right type of foundation. Total weight of the structure and self-weight of the mat is calculated and is divided by the total area of the foundation it is covering to calculate the stress on the soil.Īs in case of raft foundation the contact area of the foundation with soil is much more than any other type of foundation, so the load is distributed over a larger area and thus the stress on soil is lesser and the possibility of shear failure of soil is also reduced. Stress distribution mechanism of raft foundation is very simple. Raft foundation transmits the total load from the building to the entire ground floor area. Let’s get a quick review of its working principle. To get a better idea about when to use raft foundation, it is important to understand how raft foundation works. Raft foundation is generally used to support structures like residential or commercial buildings where soil condition is poor, storage tanks, silos, foundations for heavy industrial equipment etc. Usually, mat foundation is spread over the entire area of the structure it is supporting.
Raft foundation is actually a thick concrete slab resting on a large area of soil reinforced with steel, supporting columns or walls and transfer loads from the structure to the soil. Definition of raft foundation along with working principle, when to choose raft, types of raft foundation, materials of raft foundation, raft construction steps etc are discussed below. Raft foundation is also known as Mat foundation. The raft foundation is a very commonly used type of foundation system.
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