Construction of a deep basement with a single-level prop – prop forces and wall movements

This paper describes the construction of a deep basement in central London. The construction sequence for the basement was a combination of top-down and blue-sky excavation to enable phased delivery of the project. Temporary single-level props enabled blue-sky construction by managing ground movements. Ground movements associated with the basement construction and impact on third-party assets were monitored to validate the design using three-dimensional targets and inclinometers. The ground movements were predicted at each stage of construction using simple models with more complex three-dimensional soil–structure finite-element analysis used when examining the whole basement behaviour under the temporary and permanent loads. Temporary prop loads, and thermal loads on props were also monitored during the bulk digging. The small strain constitutive models for London Clay was shown to closely predict the observed movements.