Estimating insitu soil stiffness from changes in atmospheric pressure
The small strain elastic modulus of stiff soils can vary over many orders of magnitude for relatively small operational strains. It is important to obtain small strain modulus data (i.e. a reference modulus) for predictions of small strain ground displacement due to deep excavations. This was famously demonstrated during the construction of the underground car park at the Palace of Westminster; the Clock Tower leaned towards the adjacent excavation, rather than away as predicted (Burland, 1989).
The project will develop a methodology to measure the small strain(<0.01%), drained modulus of stiff, insitu soils by measuring piezometer response to barometric (atmospheric) loading pressure. A laboratory testing programme will provide due diligence and insitu geophysical testing (MASW) will provide comparative measurements of the in situ soil shear modulus.