The mechanistic response of an Umbrella Arch (UA) support system that is used as a portion of the overall temporary support in poor tunneling conditions (weak/loose ground/subsidence prone zones) is not currently well understood. This paper compares existing empirical solutions to existing semi-analytical solutions related to UA support systems. The results of such a comparison illustrates the fact that most of the existing models have been designed according to conditions associated with shallow excavations. To date, there is no generally accepted empirical model has been produced in order to incorporate and capture the effects of an Umbrella Arch installed at depths. Therefore, in order to analyze the mechanistic response of an Umbrella Arch system in squeezing ground conditions at depth, a three dimensional (3D) finite difference numerical model was created. A parametric analysis was conducted on the interaction parameters (stiffness parameter in the normal and shear direction of the forepole elements that constituted the UA) to find a possible range of UA element deflection profiles. These deflection profiles were then used to test and modify the pre-existing semi-analytical response. The results of this study produced a new semi- analytical model for Umbrella Arches installed in squeezing ground conditions.
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