1. Soils and Foundations

2. Foundation Loads
A foundation supports a number of different kinds of loads:
Dead Load – of the building which is the sum of the weights of the frame, the floors, roof, and walls.
Live Load – which is the sum of the weights of the people in the building, the furnishings and equipment they use, and snow, ice and water on the roof

3. Foundation Loads
Wind Loads – which can apply lateral downward and uplift loads to a foundation
Horizontal pressures – of earth and water against sub building walls
Horizontal thrusts – from arches, rigid frames, domes, and vaults
Buoyant uplift force – from underground water, identical to the force that cause a boat to float
Earthquake forces – horizontal and vertical forces caused by the motion of the ground relative to the building.

4. Satisfactory Foundation
A satisfactory foundation for a building must meet three general requirements.
The foundation including the underlying soil and rock must be safe against a structural failure that could result in collapse.
During the life of the building, the foundation must not settle by an amount that could damage the structure or impair its function.
The foundation must be feasible both technically and economically and practical to build without adverse effects to surrounding property

5. Foundation Settlement
All foundations settle to some extent as the soil adjust around and beneath them because of the load
No settlement (unnoticeable)
Uniform settlement
Differential settlement

6. Soil Classified for Engineering Purposes
Rock – continuous mass of solid mineral material
Soil – general term referring to earth material
Boulder – two hands to pick up
Cobble – one hand to pick up

7. Soil Classified for Engineering Purposes
Course Gravel Soils
gravel – can be lifted with thumb and forefinger
sand – can be seem but cannot be pick up .25 in in.
Fine gravel soils
Silt – equal dimension range in size from .002 in in
Clay – play shape and smaller then in.

8. Cohessive vs. Frictional
Clay Soils – cohesive – retain a measurable shear resistance in the absence of confining forces
Sand and Silt soils – fictional or cohessiveless – the shear resistance is directly proportional to the confining force pushing particles together.

9. Other Issues
Peat and other organic soils are not suitable for the support of buildings foundations
Water passes readily through clean gravels and sans, slowly through very fine silts and sands, and almost not at all through many clays.
An excellent way to keep a basement dry is to surround it with a thick layer of clean gravel or crushed stone. Water passing through the soil toward the building cannot reach the basement without first falling to the bottom of the gravel layer.

10. Subsurface Exploration and Soil Testing
Prior to designing a foundation for any building larger than a single family house, it is necessary to determine the soil and water conditions beneath the soil and water conditions beneath the site.
Test pits are useful when foundation is not expected to extend deeper than about 8 ft. Test water level and soil contents
Boring machines use on deeper soil test.