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Introduction to Foundation Engineering

Soil Exploration

Lateral Earth Pressure Theories and Retaining Walls

Arching in Soils and Braced Cuts

Flexible Retaining Structures and Coffer Dams

Bearing Capacity and Settlement of Shallow Foundations

Mat Foundations

Pile Foundations

Well Foundations

Foundation Soil Improvements

Foundation Engineering

The lower part of the structure which connects and transmits the load from structure to the ground soil is called Foundation. Foundation Engineering comes under the combined application of soil engineering and rock engineering (Geotechnical) which deals with the design of foundation structures.
Foundation of a structure is always constructed below the ground level for the lateral stability of the structure. Foundation of a structure acts as a firm and a level surface for transmitting the load of the structure on a large area of the soil lying underneath. The solid ground on which the foundation rests is called the Foundation Bed.

Classification
Foundations are classified under two categories:

  1. Shallow Foundations
    • Spread footing or open trench foundations
    • Grillage foundations
    • Raft foundations
    • Stepped foundations
    • Inverted arch foundations
  2. Deep Foundations
    • Pile foundations
    • Well foundations
    • Caisson foundations

Purpose of Foundation
The main purpose of the foundation is to distribute the structural load over a large bearing area without causing bearing capacity failure and excessive settlement to obtain a level and hard strata or bed for building operations to increase the stability of the structure as a whole. All engineering structures are provided with foundations at the base to fulfill the following objectives and purposes:

  1. To distribute the load of the structure over a large bearing area so as to bring the intensity of loading within the safe bearing capacity of the soil lying underneath.
  2. To load the bearing surface at a uniform rate so as to prevent unequal settlement.
  3. To prevent the lateral movement of the supporting material.
  4. To secure a level and firm bed for building operations.
  5. To increase the stability of the structure as a whole.

Factors Affecting the Selection Of Foundation
Mainly, the foundation of structures is selected on the basis of ground and load conditions. The performance of foundation is based on the interface of the load from the structure and the supporting ground soil or strata.

  1. On the Basis of Ground/Soil Condition
    • Where soil close to the surface is capable of supporting structure loads then shallow foundations can be provided.
    • Where the ground close to the surface is not capable of supporting structural loads, hard strata is searched for, and in some cases, it may be very deep, like in the case of multi-storey buildings, where loads are very high. So, deep foundations are suitable for such cases.
    • Field up ground has low bearing capacity, so deep foundation is required at that place, whereas uniform stable ground needs relatively shallow foundation.
    • The level of the ground also affects foundation selection. If the ground is not leveled and has gradient then step foundation may be preferred.
  2. On the Basis of Loads From Building
    • In the case of low-rise building with the large span, the extent of loading is relatively modest, so shallow foundation is preferred.
    • In the case of the high-rise building with short span have high loads. Therefore, the deep foundation is required in such cases. A deep foundation is provided because ground at greater depth is highly compacted.

Bibliography

  • Foundation Engineering SK Agrawal
  • Foundation Engineering SK Agrawal

 

 


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