Engineering Geology: Footings and Foundation
FOUNDATION is the lowest supporting layer of a structure. * Purpose: Transfer the building load to the soil. * The size of the foundation is determined by the weight of the building and the load bearing capabilities of the soil. * When the load bearing capabilities of the soil is low, a footing is usually used.
Types of Foundation
1. Shallows Foundations * Shallow foundations are those founded near to the finished ground surface; generally where the founding depth (Df) is less than the width of the footing and less than 3m. * Shallows foundations are used when surface soils are sufficiently strong and stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat, recent lacustrine and alluvial deposits, etc.
2. Deep Foundations * Deep foundations are those founding too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level. * Deep foundations are used when there are weak (“bad”) soils near the surface or when loads are very high, such as very large skyscrapers.
Shallow Foundation Types
1.Pad or column footings (Isolated or Combined)
Isolated - used to support single columns. This is one of the most economical types of footings and is used when columns are spaced at relatively long distances.
Combined - usually supports two columns, or three columns not in a row. Combined footings are used when two columns are so close that single footings cannot be used or when one column is located at or near a property.
2. Cantilever or strap footings-consist of two single footings connected with a beam or a strap and support two single columns. This type replaces a combined footing and is more economical.
3. Continuous footings - support a row of three or more columns. They have limited width and continue under all columns.
4. Wall Footings -
Types of Foundation
1. Shallows Foundations * Shallow foundations are those founded near to the finished ground surface; generally where the founding depth (Df) is less than the width of the footing and less than 3m. * Shallows foundations are used when surface soils are sufficiently strong and stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat, recent lacustrine and alluvial deposits, etc.
2. Deep Foundations * Deep foundations are those founding too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level. * Deep foundations are used when there are weak (“bad”) soils near the surface or when loads are very high, such as very large skyscrapers.
Shallow Foundation Types
1.Pad or column footings (Isolated or Combined)
Isolated - used to support single columns. This is one of the most economical types of footings and is used when columns are spaced at relatively long distances.
Combined - usually supports two columns, or three columns not in a row. Combined footings are used when two columns are so close that single footings cannot be used or when one column is located at or near a property.
2. Cantilever or strap footings-consist of two single footings connected with a beam or a strap and support two single columns. This type replaces a combined footing and is more economical.
3. Continuous footings - support a row of three or more columns. They have limited width and continue under all columns.
4. Wall Footings -