The development and implementation of a tunnel characterization method

Coffman, Richard A.; Garner, Cyrus D.; Salazar, Sean E.

doi:10.1002/geot.201400009

Cited by 1 publication

(2 citation statements)

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“…Such parameter is suggested to be between 0.3 % to 0.6 %, with a maximum value of 1% (Gatti and Cassani 2007). Coffman et al (2014) extensively discussed the relation between the CI and ground loss (g%) using data from several projects. They introduced an exponential relation between g and CI parameters, stating that CI might exceed the offered values depending on local site conditions.…”

Section: Settlement Induced Damagementioning

confidence: 99%

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Tunneling Excavation Induced Settlements in Granular Soils:Case of Keçiören Subway (Ankara)

Sojoudi

Ulamiş

Kılıç

2021

Preprint

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The need for underground transportation is increasing to reduce traffic within metropolitan cities. During excavation, ground loss within the soft soils and associated ground settlements might occur. Tunneling induced ground settlement has to be within tolerable limits. Otherwise, damage to ground level and infrastructures are experienced. In this study, reasons of ground settlement occurred during the excavation of twin subway tunnels at Keçiören (Ankara) are evaluated. In 2006, the first phase excavation caused ground settlement with no considerable damage. The second phase excavation started in 2012, both within the saturated sandy and gravelly soils of Çubuk Creek’s alluvium. At the time, several collapses and associated ground settlements were reported. Due, an investigation program started including resistivity surveying, borehole drilling and in-situ testing. Since ground settlements were known, back calculation was performed to obtain the settlement trough, inflection point and the change of contraction increment. Moreover, the stress conditions and external stresses exerted by existing structures are reviewed. Collapses with volume up to 80 m3 were observed nearby the buildings and free field during the second phase excavation which were determined through 2D resistivity data and boreholes. It was concluded that, the change of settlement at ground level and on the tunnel segments are related to contraction increment based on the numerical modelling of the twin tunnels. Possible reasons for collapse can be listed as TBM cutting head and shield defect, change in ground structure due to underground water level changes, and the impact of the previously excavated tunnel in 2006.

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Section: Settlement Induced Damagementioning

confidence: 99%

“…The contraction increment is related to the ground loss and might reach up to 16% which correspond to a ground loss of 4.82% (Coffman et al 2014). Based on this, the FEM model was run to evaluate the effect of CI on settlement values.…”

Section: Numerical Modellingmentioning

confidence: 99%