Ground movements due to underground construction and impact on the built environment
Ground movements due to underground construction and impact on the built environment
A – Finite element analysis of tunnel-soil-building interaction scenarios
It is possible to develop detailed 3D finite element models to predict the way in which buildings respond to the construction of shallow tunnels. However, to conduct risk assessments on the large number of buildings that are typically considered at risk in major urban infrastructure projects, simplified models are needed. Research is being conducted on numerical models at a variety of levels of complexity from full-coupled 3D finite element models as shown in Fig 1a to simplified approaches as illustrated in Fig 1b in which specially-formulated soil-foundation elements remove the need to include the soil (and tunnel) explicitly in the model. New methods to idealise the structure with new reduced-order finite element models are also explored in this research.
Fig 1a – Fully coupled 3D finite element analysis (Yiu et al. 2017)
Fig 1b – Simplified S2M model (Burd et al. 2021)
B – Large scale tests
The Oxford team is contributing to a set of tests in Turkey (see Fig 2). The tests are being led by Dr Deniz Dalgic, with the support of the company Fibrobeton. The Oxford team designed detailed instrumentation to monitor the strains and displacements the developed in four two-storey building models when ground-level movements (simulating tunnel construction) are induced by jacking. When complete, the test data will support the development of new assessment models, improve existing monitoring approaches and propose reversible and sympathetic techniques with fibre-reinforced plaster materials to prevent damage. The project was awarded the IStructE 2020 Research Award.
Fig 2a – Large-scale settlement tests on masonry buildings
Fig 2b – Point cloud of St Mary Abchurch
C – Field monitoring
The Oxford team has experience in developing and deploying monitoring techniques to support underground construction activities in the vicinity of high value assets. The collaborative work conducted in collaboration with Transport for London involved monitoring Grade-1 listed buildings (St Mary Abchurch and Mansion House) with a range of techniques. The data helped prevent unnecessary mitigation measures. The project was awarded ‘Research Impact Award’ at the 2018 NewTechFest and ‘Instrumentation and Monitoring Award’ at the 2018 Tunnelling Festival.
D – New computer vision systems
Research is underway, supported by Arup (Ben Gilson and Michael Devriendt), on the development of new computer vision-based systems for the monitoring of masonry assets that are subjected to construction-related ground movements. It seeks to develop (i) new point cloud comparison techniques to enable non-contact and full-field displacement monitoring of field structures with laser scanners, and (ii) new virtual tell-tales which will enable non-contact crack measurements from inspection photographs for use in future construction activities.