Foundation is the most significant part of any structure/building which transfers the total loads of the structure and its components to a competent surface on the ground. Foundations are broadly classified into two types. ie. Shallow and Deep Foundations.
Foundation is the last part of the structure which touches the ground. The area of contact with the ground is called the foundation bed.
Every structure is divided into:
a) Sub structure
b) Super structure
Components of a structure that are coming below the ground level are called substructure, and above ground level is called superstructure. Foundations are coming in the substructure category. Foundations are responsible for transferring loads of superstructure components to the ground.
HOW TO FIX TYPE AND SIZE OF FOUNDATIONS?
The selection of foundations depends on the bearing capacity of the soil and the purpose of the structure. Geotechnical engineering is a field of Civil Engineering, which analyses the physical and chemical properties of soil and furnish designers with the inputs on the soil properties and proposed types of foundations. The Safe bearing capacity of the soil determines the foundation type and dimensions.
SAFE BEARING CAPACITY OF SOIL
Bearing capacity is the capacity of soil to support a structure without settlement or failure. To keep the structure safe, the bearing capacity has to be calculated at different locations. The ultimate bearing capacity has to be divided by a factor to derive the safe bearing capacity of the soil. Safe bearing capacity is defined as the maximum load per unit area soil can withstand without settlement and failure. The safe bearing capacity is determined by conducting field tests or soil investigations.
QUALITIES OF A WELL DESIGNED FOUNDATION
A well-designed foundation is supposed to possess the following qualities.
a) Have to distribute the total load on the structure to a larger area.
b)Have to counter unequal settlement in case of any displacement.
c) Has to prevent the structure from lateral moments.
d) Foundations are responsible for the total stability of structures.
DIFFERENT TYPES OF FOUNDATIONS
Foundations are classified into
a) Shallow Foundation
b) Deep Foundation
Shallow foundations transfer the load laterally to the soil. It is also called stripped foundations. The depth of a shallow foundation is less than its width.
Characteristics of shallow foundations
Shallow foundations are adopted when the load acting on a structure is reasonable and has a competent soil layer capable of negotiating the loads available at a shallow depth or shorter depth.
Shallow foundations are placed on the surface of the ground. The depth of a shallow foundation can range from 1 meter to 3.5 meters and sometimes more.
The width of the shallow foundation is greater than the depth. Shallow foundations are very easy to construct and do not require highly skilled manpower and professional supervision. These foundations can even be done with the help of medium-skilled workers. A shallow foundation is very economical when compared with a deep foundation. Shallow foundations are end bearing type foundations that transfer loads to the end of the foundation.
Shallow foundations are considered as the most preferred option when the safe bearing capacity of the soil is reasonable and the structural loads are within the permissible limits.
Characteristics of deep foundation
The width of the deep foundation is less than the depth. The depth can even go up to 60 meters or more depending on the design, loads, and availability of capable strata.
Deep foundations require technical expertise, sophisticated equipment, and highly skilled manpower for interpreting and executing works.
The deep foundations are costly due to their way of execution involving the infusion of quality materials, skilled labor, professional engineering support, and equipment
Deep foundations do not rely only on end bearing for transferring the loads. The skin friction developed between the foundation surface and the soil surrounding it may also be considered in the design stage.
The deep foundations can resist uplift pressure much more than shallow foundations and hence the chances of failure are less compared to shallow foundations.