Maximum pressure a foundation soil can support without shear failure.
Ultimate bearing capacity (Terzaghi): q_u=cN_c+qN_q+½γBN_γ; allowable q_a=q_u/FS (≈3) subject to settlement limits. Depends on footing size, depth, soil strength and water table. Settlement often governs in clays and loose sands.
A 2 m square footing on dense sand may carry several hundred kPa.
Bearing capacity sets the maximum load a foundation can carry safely, so it decides the size and depth of footings.
Maximum pressure a foundation soil can support without shear failure.
Bearing capacity sets the maximum load a foundation can carry safely, so it decides the size and depth of footings.
The ultimate capacity is the load causing failure, and the allowable value divides it by a factor of safety to give the design pressure.
Soil strength, footing width and depth, the water table and the shape of the foundation all influence the result.
Typical applications include sizing a pad footing under a column in a building, checking whether a shallow foundation on soft clay will fail and deciding whether a raft foundation is needed for a heavy structure.
Study "Shear strength of soil" first (topic 33 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
Shear failure modes. Net vs gross pressure. Eccentric loads.
A 2 m square footing on dense sand may carry several hundred kPa.
The next topic is "Shallow foundations", which builds directly on this one.
It is classed as Beginner in Civil & Structural (topic 34 of 112). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.
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