Foundation depth in clay soil | best Foundation type for clay soil | minimum and maximum depth of foundation in clay soil | what type of foundation is best for clay soil | how deep footing in clay | how deep do footing need to be in Clay soil.
A foundation/footing is a lower portion of building structure or substructure that transfers its all coming loads of structure to the ground. The design of size and depth of foundation depends on the total load on the building and the type of sub soil and its bearing capacity.
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Foundations are generally broken into two categories mainly, shallow foundations and deep foundations.
Foundation with depth less than 3 meter are shallow foundations. Such foundations are used for structures that do not carry much load. They are also used in case the soil has high bearing capacity. Examples of Shallow Foundation is isolated footing, combined footing, strap footing and raft footing.
Foundations with depth greater than 3 meter are deep foundations. They are deep below the finished ground surface such that their base bearing capacity is not affected by surface conditions. Examples of deep Foundation is Pile and piers formation.
The choice of the appropriate type of foundation is governed by some important factors such as the nature of the structure, the loads exerted by the structure,The subsoil characteristics and the allotted cost of foundations.
Clay soil have high moisture content about 40% of water when there is presence of tree near by their moisture content is differential increases, clay soil is not suitable for foundation of building, because of its squeezing nature, I moiture content, swelling and shrinkage nature in rainy and summer season respectively.
Swelling and shrinkage of clay soil results extra pressure on foundation, swelling nature creates upward push pressure on foundation of footing and shrinkage nature creates downward pull pressure on foundation, this leads to unstability of foundation crack in footing and roof and maybe leads to structural failure, its needs extra care when building foundation is layout on clay soil.
Foundation depth in clay soil | best Foundation type for clay soil
What are the problems created foundation in clay soil? Soils rich in clay and silt have the greatest potential to damage a foundation. Clay absorbs water easily, expanding in volume as it becomes more saturated. So-called “expansive clays” can cause foundations to crack, heave and shift.
When clay soils dry out, they shrink and crack, leaving gaps around a house where water from the next storm can penetrate easily and repeat the expansion cycle. Clay-rich soils can cause more foundation damage by expanding than by contracting.
There is different grade of clay soil present in all over the world United States of America, England, continent Asia and India. First Clay soil with the higher plasticity have higher moisture content, and their expansion and contracting volumetric change is increase that is more adversely affect on foundation of building, 2nd type clay soil have medium plasticity have Less moisture content compared to high plasticity, its moderate effect on foundation, third type clay have low plasticity,less moisture content,at low risk for foundation of building.
Foundation depth in clay soil:- Foundation depth in clay soil depend on plasticity nature of volumetric expansion and contracting, depth of foundation of footing in clay soil of higher plasticity, it could be 1m (1000mm) deep, of medium plasticity, it could be 0.9m (900mm) deep and for low plasticity, it could be 0.75m (750mm) deep beneath the soil where hard strata of soil have been found.
Minimum depth of foundation in clay soil:- according to volumetric changes expanding and shrinkage nature and plasticity condition, minimum depth of foundation of footing in clay soil is kept around 0.75m(750mm) deep beneath the soil where hard strata of soil have been found.
Maximum depth of foundation in clay soil:- according to volumetric changes expanding and shrinkage nature and plasticity condition, maximum depth of foundation of footing in clay soil is kept around 1m(1000mm) deep beneath the soil where hard strata of soil have been found.
How deep should Foundation be in Clay soil:- it is not easy task, first we do soil test, it is either clay soil with higher plasticity or low plasticity get the report, higher plasticity and higher risk of foundation of footing, lower plasticity, low risk of foundation of footing of building. Foundation of footing should be 1m to 3m deep in clay soil, where hard strata of soil have been found.
What type of foundation is best for clay soil? Usually clay has a higher moisture content and when the moisture content becomes stable upto certain depth it becomes suitable for the substructure. Raft foundation is best to use when the clayey soil is compact and hard. Even strap foundation can also be used. Soft clayey sand is prone to expansion and shrinkage need to be provided with pile formation.
What Foundation is suitable for clay soil? Raft foundation is suitable when the clayey soil is compact and hard bearing low plasticity. strap foundation can also be used for medium clay of medium plasticity, Soft clayey sand is prone to expansion and shrinkage need to be/more suitable provided with pile formation.