Foundation and overall structure designs of continuous spread footings along with soil spatial variability and geological anomaly

•Foundation and overall structure designs of continuous spread footings are compared.•Spatial variability of soil modulus is modeled by geostatistical methods using real data.•Presence of geological anomaly increases settlement and bending moment estimations.•Load redistribution effect reduces bending moment but it cannot completely absorb it.•Overall structure design appears more appropriate approach in presence of geological anomaly.

Spatial variability of soil properties and geological anomaly can be very important in the case of low weight buildings with continuous spread footings inducing differential settlements which can have harmful consequences on the structure. They are also the major source of uncertainty in the choice of the soil design parameters. In this study, the design of continuous spread footings is performed with two approaches: the first approach with a foundation design using a one-dimensional finite element modeling and the second approach with an overall structure design using a three-dimensional finite element modeling. These approaches are compared for two cases: the first case dealing with the spatial variability of soil modulus and the second case with the spatial variability of soil modulus coupled with the presence of a geological anomaly (low stiffness zone of soil). Spatial variability of soil modulus is modeled by geostatistical methods using data from a real construction site. The values of the maximum settlements, maximum differential settlements and maximum bending moments obtained from the both approaches for the first case are nearly close together where the latter values for the second case are significantly greater than the first case. These results show that in the case of the presence of a geological anomaly on the construction site, the overall structure design appears the more appropriate approach compared to the foundation design in the design of continuous spread footings.