Leveraging FEA and InSAR for Accurate Settlement Analysis
Hutton Hub - Hertfordshire, United Kingdom
Highlights
-
Extensive site investigation data allowed the top of chalk and infill properties to be mapped in detail.
-
The geometrical detail was transferred to a 3D FEA model of the raft foundation.
-
Differential settlements were found to be within acceptable limits for the glazed facade.
-
18-month post-construction settlements measured by DInSAR were less than 3mm.
-
Bending moment and shear force output were used in the structural design of the raft.
The University of Hertfordshire’s new Hutton Hub building, designed for the Student Union, featured a distinctive glass façade that required precise control over differential settlement of its foundation.
​
Given the complex conditions at the site, this was a significant challenge. The site investigation revealed a vast network of solution and mining features beneath most of the building’s footprint, with depths reaching up to 25 meters. The infill varied considerably, from soft clay spots to dense sand and chalk, conditions that made differential settlement a major concern. This ruled out the use of a raft foundation, leading to the recommendation of piled foundations.
​
In the event a raft foundation could have been feasible, the structural engineers needed detailed spring stiffness values and other soil-structure outputs to account for the complex ground conditions. The site had already undergone extensive investigations in multiple phases, allowing for precise mapping of the infill properties in three dimensions.
​
To address this, a 3D Finite Element Analysis (FEA) model was created using advanced FEA software. The finite element method (FEM) allowed for the detailed simulation of the raft foundation and the supporting ground, incorporating material properties and boundary conditions. The model also included shear and core walls to account for their stiffening effects. Structural loads were simulated to analyse how the raft foundation would perform under various conditions.
​
The final result showed that the raft foundation could effectively span the soft spots in the infill, with predicted differential settlements significantly lower than those projected by conventional analysis methods. These findings were further validated by InSAR (Interferometric Synthetic Aperture Radar) analysis to detect surface deformation. The InSAR data revealed less than 3mm of settlement in the 18 months following construction, confirming the accuracy of the FEA model.
​
The successful application of FEA and InSAR technologies led to the adoption of the raft foundation, avoiding an additional cost of around £1 million for planned foundation piling. This also prevented associated delays and reduced CO2 emissions from piling operations.
