Chapter 5: Shallow Foundations - Ultimate Bearing Capacity

What are the different types of shallow foundations and why is bearing capacity important?

Spread footings, strip footings, mat foundations; bearing capacity ensures soil can support loads without shear failure

What is the ultimate bearing capacity of a shallow foundation?

The maximum pressure soil can support before shear failure

How is Terzaghi’s bearing capacity equation used?

Uses c′, φ′, γ, and foundation dimensions to estimate ultimate capacity

Why is a factor of safety applied to bearing capacity?

To prevent failure; allowable capacity = ultimate / FS

How does the groundwater table affect bearing capacity?

Higher water table lowers effective stress and reduces soil strength

What is the general bearing capacity equation?

Includes shape, depth, and load inclination factors for more realistic conditions

Why are additional bearing capacity factors used?

To account for foundation shape, depth, and loading variations

Why are case histories important in bearing capacity analysis?

They show real failures/successes and validate design methods

How does soil compressibility affect bearing capacity?

High compressibility can cause excessive settlement before shear failure

What is the scale effect in bearing capacity?

Larger foundations may have different capacities due to stress distribution

How is bearing capacity estimated for eccentrically loaded foundations?

Load offset reduces effective area, lowering capacity

How is one-way eccentricity handled in bearing capacity?

Reduce width: B′ = B − 2e

How is two-way eccentricity handled in bearing capacity?

Reduce width and length: B′ and L′

How is a continuous foundation analyzed under eccentric inclined load?

Account for both eccentricity and load inclination in capacity calculations