Advancing Design Models for Estimating Groundwater Inflow in Underground Construction
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Authors
Markus, Simone
Date
2025-10-27
Type
thesis
Language
eng
Keyword
tunnel , groundwater , numerical modelling , finite element method , rock mechanics , inflow , cavern
Alternative Title
Abstract
This research aims to validate and test the limits of analytical solutions for estimating tunnel and cavern groundwater inflow and uses numerical modelling to assess the impact of different boundary conditions and complicating factors such as heterogeneity, anisotropy, precipitation, irregular geometry, and three-dimensional and transient flow. When these factors are considered, it becomes apparent that simple analytical solutions lose validity, and a more detailed approach is required.
As groundwater inflows are difficult to measure, and real-world data does not allow for the isolation of factors influencing flow, this thesis relies on numerical models to perform this validation, completing multiple sensitivity analyses using 2D and 3D FEM modelling for tunnel inflow. Results are compared with analytical solutions, in order to provide guidance on their use, and in some cases to propose new semi-empirical methods, where analytical solutions fall short.
The major contributions of this thesis to the field of tunnel groundwater inflow are as follows:
• A new semi-empirical method for relating tunnel groundwater inflow to excavation induced drawdown, which considers the distance to a source of recharge.
• A semi-empirical method for estimating how long after tunnel excavation it will take for inflows to reach a steady state, based on rockmass hydraulic conductivity, initial head above the tunnel, and distance to a source of recharge.
• For tunnels in anisotropic and heterogeneous rockmasses, including tunnels in and below aquifers, guidance is provided for use of existing analytical solutions for inflow, with suggested modifications.
• Discussion on how precipitation rates relate to model boundary conditions and groundwater drawdown.
• For groundwater inflow into caverns, an example is provided which demonstrates that analytical solutions will underpredict groundwater inflow.
• For predicting transient inflow into tunnels during excavation, examples demonstrate that over a period of one year, with an advance rate of 2-4 meters per day, that total inflows will be approximately 1.8-2.1 times that which would be predicted by steady state methods.
These contributions allow for site-specific characteristics to be taken into account for groundwater inflow estimation in early phases of projects. Guidelines for dealing with each complicating factor are summarized in the conclusions chapter of this thesis.
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Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution-ShareAlike 4.0 International