Principle of Floating Foundation

2023-04-11 01:37:47 -0500

What is a Floating Foundation and how do you define it?

floatingfoundation is a foundation that is excavated in soil so that the structure is almost equal to the soil's total weight, including any water. The floating foundation, also known as balancing raft, causes no settlement.

Principle of Floating Foundation

The principle behind floating foundation is to equalize the soil's weight with a structure that has the same weight, causing zero settlement. This foundation is also known as the balancing foundation.

Let's take a ground with a water table at its top, as shown in the picture above. Excavated to a depth below the water table, the ground is then excavated.

In the next step, a structure is built that is equal in weight to the soil and water. Even though excavation depth is lower than the table, the soil's total vertical pressure below the foundation remains the same because of the balancing weight.

One thing to keep in mind is that we can't build a structure right away after excavation. Unbalanced weight can cause the effective vertical pressure to rise slightly during construction. This type of foundation can be called partially compensated foundations, instead of fully floating foundations or compensated foundations.

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Suitability of Floating Funds

For the following soil types, floating foundations are ideal:

Good shear strength soils that are prone to large settlements or differential settlements when subjected to heavy loads. A floating foundation is an option that can help reduce settlement values.

Low shear strength soils with no hard layer at a reasonable depth. Floating foundation is used to lower the shear stresses and prevent settlement.

Construction of a Floating Foundation is a difficult task

You can prevent problems from arising during the construction of floating foundations by being careful. During construction of floating foundation, problems may arise.



Critical depth

Bottom heave

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It is important to carefully excavate the floating foundation. Sheet piles, timber piles, or soldier piles should be used to support the walls of the excavated area.


Dewatering is necessary if the excavation depth is below the watertable. Before you dig, it is best to check the water table level. Be careful when dewatering, as it could cause the water table to drop and disturb adjacent structures.

Benefits of floating foundation

Sites with lower soil bearing capacity (SBC), are advantageous

Reduce the foundation settlement

Use in high-moisture soils

Stabilizes the structure.

It can be used in soils with variable compressibility or over loose soil.

When we need to extend the building without affecting the foundation, it is effective

Because deep footer trenches don't exist, it requires less digging

This helps to prevent water seepage and frosting from leaking

These are the steps for foundation settlement

Site preparation - The site is first checked. The dirt and trespasses are then removed. Next, excavation begins.

Site Excavation for Floating Foundation - Clear the land and excavate as per the plan. This is the first preparation for construction.

Laying Gravel Base to Drainage - allowing water to drain through the gravel base.

Reinforcement Of Floating Fund- Molds are used for the casting process.

Formwork is poured with Floating Slab- concrete after casting.

Curing should take seven days. For curing, water is used.

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