A worker laying the foundation using a hammer.

Any structure consists of two parts, a sub-structure, and a super-structure. These two parts of a structure are separated by a line called the plinth of that structure. The plinth is typically the top of the foundation wall. The sub-structure is the part below the plinth and the superstructure is the part above the plinth level.

As the foundation is one of the most important parts of the structure, the design and construction of it should be precise and cannot be neglected. The main concerns of designing a foundation are bearing capacity of soil and settlement in the soil.

FOUNDATION ENGINEERING is a branch of civil engineering which involves the study and design of sub-structure that is the study and design of structure below the plinth level. It is applied soil mechanics and findings in the design of foundation elements of a structure. A foundation is the part of the structure that bears the load of the superstructure. Also, the foundation transfers load from the structure to the ground/soil.

Foundation design is a process of designing the footing and foundation walls of the structure. The footing can be of many varieties, for example, strip or continuous footings, drilled piles, mat foundations, etc. Designing a foundation is dependent on the geotechnical report. According to the geotechnical report, it is decided whether the structure should have a deep foundation or a shallow foundation.

SHALLOW FOUNDATION:

Shallow foundations are constructed where the hard strata are extremely near the ground surface rather than deep down the sub-layers of the ground, or the quality of the topsoil is sufficient forbearing. Common types of shallow foundations are continuous wall footings and pad or mat footings.

DEEP FOUNDATION:

If the depth of the foundation is more than five times the width of the footing of foundation, it is considered as a deep foundation. Deep foundations need to be constructed where the hard strata or the rock strata is deep into the sub-layers of the ground, or where the soil is poor in quality. This also may be required when construction on hillsides or in water-saturated areas.  Drilled piers are the most common deep foundations, but others include driven piles and helical piers. These foundations help to avoid differential settlement and total settlement in larger structures or anchor smaller structures in less than ideal conditions.

The process of designing a foundation consists of the following activities: 

·Basic site survey.

·Geotechnical survey.

·Checking of bearing capacity of soil and depth of soft and hard strata.

·Consultation of a structural engineer.

·Design of footing.

Proper design of the foundation system is extremely important as foundation or substructure is one of the most important parts of any structure.

After the design and construction of the footing, maintenance is also very important. A regular inspection like settlement, stress, strain, etc on the foundation and monitoring are good ways to ensure the foundation stays effective.

An engineer standing outside inspecting a crack in the main rear wall.

BASIC REQUIREMENTS OF A GOOD FOUNDATION:

As the foundation is one of the most important parts of the structure, the design and construction of it should be precise and cannot be neglected. The main concerns of designing a foundation are bearing capacity of soil and settlement in the soil. Differential settlement is the settlement where one part of the structure settles much more than the other one. Also, total settlement involves a total of uniform settlement as well as differential settlement. The geotechnical engineer designs the foundation for geotechnical conditions and considering the bearing capacity and design loads of the structure. And the footing should be designed by a structural engineer because the footing is a member of structural elements like beams, columns, etc.

Other important aspects to design a good foundation are as follows:

·The design and construction of a good foundation should be carried out in such a way that it can transfer all possible loads to the ground without causing any settlement in the soil mass, including gravity loads and potential lateral loads from wind or seismic activity. 

·If the superimposed loads are not uniform in nature, the structure is prone to differential settlement. Differential settlement can be avoided by providing a rigid base or larger spread footings to the foundation in such areas.

·Because of temperature changes, shrinkage and swelling are the major problems. To avoid these problems, a slightly deeper foundation should be constructed in areas with extreme weather conditions.  Rebar reinforcement is also important in the design under these conditions to mitigate and control cracking.

·Planning of the foundation area should be done considering the future works don't interfere and alter any existing foundation. If you plan to add to the house, later on, be sure to consider this when designing the foundation.

·Expansive clay soil is also an extremely problem-causing soil type as there is a lot of settlement in this type of soil because of low bearing strength. Adequate drainage should be carried out in this type of soil to construct a safe foundation. Watch out for these and make sure to obtain a geotechnical report.

FOUNDATION INSPECTION:

After the design and construction of the foundation, the maintenance of the foundation should be carried out properly. To carry out the maintenance work, the sub-structure needs to be inspected. There are a lot of companies that carry out foundation inspection. If the structure is old and the foundation is in poor condition, the life of the structure can be increased by reinforcing the foundation and some key members of that particular structure. This amazing process of increasing the lifespan of a structure by reinforcing some members is known as retrofitting. Foundation design and inspection are carried out under the directions of a structural engineer.

With the structural engineer, the geotechnical engineer also plays a very important role in designing and maintaining a foundation with time to time inspection and taking note of settlements in the soil. A geotechnical engineer provides the information needed to design the foundation by testing and analyzing the soil. You can also visit our website to get more information. Contact us for a detailed and furnished plan under professional guidance. Let us help you with your project; contact us at (877) 427-5585 for a free consultation.

*Note: The content published above was made in collaboration with members of Design Everest.

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