Transient ground response during and after tunnelling
File(s)
Author(s)
Xue, Shuai
Type
Thesis
Abstract
The primary objective of the study is to advance the comprehension of transient mechanisms of ground response around tunnels during their construction, concentrating on displacements measured in the short and long term. Valuable information was acquired from the comprehensive field monitoring research relating to the Crossrail tunnelling project in London. This allowed valuable insights to be gained into ground responses at the surface and subsurface that occur during and after tunnel construction. Comprehensive and high-quality field monitoring data from the Jubilee Line Extension (JLE) Project at St James’s Park and Southwark Park were analysed as well as the data from the Crossrail Project at Hyde Park, along with other worldwide tunnelling case histories. In examining the transient ground responses induced by tunnelling, both surface and subsurface displacements, in transverse and longitudinal senses, were investigated. Variables such as volume loss, trough length and width parameters and deflection ratio, relating to tunnel construction processes, are determined in conjunction with other factors (operational parameters, parameters of tunnels and geological environment) that may affect the ground responses during and after tunnelling.
The main thrust of this research primarily concentrates on the tunnelling-induced ground responses at the surface and subsurface in the short-term, using the comprehensive field monitoring results from the Crossrail (subsequent named as Elizabeth Line) Imperial College research site at Hyde Park. Subsequently, the field data collected from the two JLEP research control sites at St James’s Park and Southwark Park were revisited to investigate the transient ground response in a similar fashion to those for the Crossrail tunnels beneath Hyde Park but relating to different ground conditions and tunnelling methods. Based on the analyses and interpretation of the monitoring data from the different cases, the responses are unified as far as possible, using various normalisation approaches, to allow overall generic ground responses to be compared and provide guidance for future projects.
The transient ground responses during tunnelling can roughly be classified into three phases, with the end of short term regarded as the end of phase 2 or start of phase 3. The definition of ‘end of short-term’ helps to identify the boundary marking the end of short-term and the start of long-term tunnelling-induced ground responses. The study has verified that the lateral extent of transverse settlement trough is largely dependent on the tunnel depth and tunnel diameter (C/D ratio), regardless of tunnel excavation method. The quantitative identification of lateral extent based on settlement concentrations (low, intermediate & high level), allows the boundary of tunnel impacted ground to be identified and potential impacts to surrounding structures assessed. From a subsurface perspective, relationships between tunnel settlement trough parameters and depth are investigated in transverse and longitudinal senses, allowing comparisons to be made between 3D ground responses. Additionally, the post-construction period ground responses are investigated for the tunnelling cases, to help understand the time-dependent ground responses in the long term and compare them with those relating to the short term.
The main thrust of this research primarily concentrates on the tunnelling-induced ground responses at the surface and subsurface in the short-term, using the comprehensive field monitoring results from the Crossrail (subsequent named as Elizabeth Line) Imperial College research site at Hyde Park. Subsequently, the field data collected from the two JLEP research control sites at St James’s Park and Southwark Park were revisited to investigate the transient ground response in a similar fashion to those for the Crossrail tunnels beneath Hyde Park but relating to different ground conditions and tunnelling methods. Based on the analyses and interpretation of the monitoring data from the different cases, the responses are unified as far as possible, using various normalisation approaches, to allow overall generic ground responses to be compared and provide guidance for future projects.
The transient ground responses during tunnelling can roughly be classified into three phases, with the end of short term regarded as the end of phase 2 or start of phase 3. The definition of ‘end of short-term’ helps to identify the boundary marking the end of short-term and the start of long-term tunnelling-induced ground responses. The study has verified that the lateral extent of transverse settlement trough is largely dependent on the tunnel depth and tunnel diameter (C/D ratio), regardless of tunnel excavation method. The quantitative identification of lateral extent based on settlement concentrations (low, intermediate & high level), allows the boundary of tunnel impacted ground to be identified and potential impacts to surrounding structures assessed. From a subsurface perspective, relationships between tunnel settlement trough parameters and depth are investigated in transverse and longitudinal senses, allowing comparisons to be made between 3D ground responses. Additionally, the post-construction period ground responses are investigated for the tunnelling cases, to help understand the time-dependent ground responses in the long term and compare them with those relating to the short term.
Version
Open Access
Date Issued
2023-04-21
Date Awarded
01/08/2023
License URL
Advisor
Standing, Jamie
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)