However, it is required to consider the water pressure on the basement slab during the operations. there will not be water inside the excavation. If the area to be built is covered with shorings such as sheet pile walls, secant piles, etc. Usually, these slabs are designing for uplift forced applied on the basement slab after the construction only. Further, they are constructed in several stages.įurther, there could be several levels in the basements. Mostly the basement floors are constructed below the groundwater table. The base slab should be designed for the pressure applied by the water and soil pressure due to loads from the tank.

The factor of safety against uplift pressure = weight of the structure/uplift force > 1.2.

If dewatering is done until the structure gains its strength, the total weight of the structure could be considered for evaluation of the factor of safety against uplift. In such situations, part of the structure to be constructed in the first stage shall be considered for the weight calculations. The weight shall not be the total weight of the structure if stage construction is done without dewatering.

Calculate the weight of the structure.

Calculate the uplift force as per the above equation.

The following procedure could be used to check the uplift. Generally, the factor of safety against uplift is in the range of 1.2 – 1.5. Uplift Force = ϒ wh A Factor of Safety Against Uplift Pressure

The following figure indicates a tank constructed under the ground.Īs indicated in the above figure, uplift pressure will be applied to the foundation. Further, it could lead to structural failure. Let’s see what the structures that we need to consider the uplift pressure.ĭesign of Underground Tanks for Uplift PressureĪ tank constructed below the water table will be floated on the water if we don’t consider the upward pressure by the water.

Knowing how to calculate the uplift pressure is very important for structural engineers as mostly many structures are constructed below the groundwater table. When the depth of the excavation is deeper, the greater the upward pressure applied by the water. Uplift pressure is a design load to be considered for the structures constructed below the groundwater table.

Hydrostatic force in a water tank