Uplift occurs when pore-water pressure under a structure or a low permeability confining layer becomes larger than the mean overburden pressure.
The water level can vary due to varying recharge rates (such as high rainfall). If the upward forces become higher than the downward forces the whole structure can be uplifted.
The design of the structure has to overcome the risk of uplift forces from the groundwater beneath, that could be present during both temporary and permanent works.
OGI’s approach is to use the available site investigation information to assess all the different scenarios that show a risk of excessive uplift forces (different water levels, excavation and construction stages, changes in the structure’s state, etc.)
For each scenario the Factor of Safety is calculated as the relationship between the uplift forces and the resistant forces.
OGI can prepare a suitable design that combines a drainage system to relieve the water pressure and improvements to a structure to provide greater resistance against uplift forces.
The design has to be checked against failure in accordance with Eurocode 7.
By application of a finite element mathematical model, OGI can analyse the elasto-plastic stress deformation in order to determine the behaviour of the structure and ground after the implementation of designed improvements.