Foundations Flashcards
What are the functions of foundations
To transmit combined foundation and ground loads (dead, live, wind),
Any movement of the ground caused by swelling, shrinkage, or freezing of the subsoil, should not impair the stability of the building
What are the 5 types of soils found ?
Rocks
Classified as igneous, sedimentary and metamorphic
Ie granite (high bearing capacity), hard limestone
Non- inclusive soils
Ie Gravel and sand (bearing capacity depends on density, grading and particles size)
Cohesive soils (sticks together)
Ie Clay settle
Peat and organic soils
Made of fibrous vegetable matter, clay or sand silt (not stable ground for foundations)
Made up ground
Variety of material & variable compaction and settlement (unsuitable for foundations)
What are the three main types of loads on foundations
Dead loads - static or constant weight created by the buildings, materials and structural elements. Ie external and internal walls, Floors, doors, windows, ceilings, roofs ,basement
Live loads- known as impose loads. They are moveable loads ie furniture, white goods, people etc. also includes variable loads caused by weather conditions such as rain or snow
Wind loads - (earthquake load) can be positive or negative. It’s the load placed on a structure by wind. Loads are calculated to combat this in high structures
What are the two types of foundations
Shallow
Deep
What are shallow foundations ? 3 points
Found near the finished ground surface
Depth is generally less than the width of the footing, less than 3m.
Shallow foundations are strip (trenchfill), pad, raft and short bore pile and beam
Unsuitable in weak or highly compressible soil
What are deep foundations ? 7points
Found deep underground, greater than 3m
Used for structures with high loads, like deep basements and multi- storey structures
Where the soil is weak
Used when trees and vegetation are near the structure
Include pile, peers and compensated foundations
What are the 4 types of strip foundations ?
Traditional shallow strip foundations
Wide strip foundations
Deep strip foundations
Trenchfill
Draw a strip foundation
Where is a pad foundation used and draw it
Used under isolated piers or columns
Where is a raft foundation used (2 points) and draw it ?
Used for lightly loaded structures on soils with poor bearing capacity heavily loaded frame structures,
Where is short bore pile and beam foundation used and draw it
Used when strip foundation is unsuitable due to ground conditions.
Usually depths of 2-3m long piles
What are the 6 advantages of short, bore pile and beam foundations ?
Clay heave or shrinkage is not affected in clay soils
Groundwater can percolate between piles
Tree roots have little effect
No dewatering is required when piling
Less concrete used then strip
Uses precast connect beams, saves time
What are the 2 disadvantages of short bore pile and beam foundations
The technique require specialist plant and labour
Piling requires a pile rig
What are the 4 main types of materials use for pile foundations?
Timber, steel ,concrete and composite piles
What are the 2 functions of pile foundations?
To transmit a foundation load to a solid ground
To resist vertical, lateral and uplift load
