The Near-Face Displacement of D-Shaped Tunnels in Isotropic and Anisotropic Media   Miguel A. Nunes Graduate Student Department of Civil Engineering and Applied Mechanics McGill University, Montreal, Quebec, Canada E-mail: miguel.nunes@mail.mcgill.ca Mohamed A. Meguid Assistant Professor Department of Civil Engineering and Applied Mechanics McGill University, Montreal, Quebec, Canada E-mail: mohamed.meguid@mcgill.ca
			ABSTRACT

Tunnels are crucial structures in the operation of many Civil Engineering works mainly because there are unique characteristics involved in designing and constructing them, namely the in-situ stresses due to overlaying rock or soil. Elastic theory has proven to be a useful aid in finding solutions and predicting accurately the displacements and stresses that arise from creating an opening within the ground. To this end, much work exists in the literature which addresses tunnel excavation by either investigating only the plane-strain deformations, or by studying the entire displacement profile of the tunnel periphery for the case where there is a uniform in-situ stress distribution in every direction. This paper seeks to conduct a broader investigation into the effects of elastic bi-directional in-situ stress distributions in both isotropic and anisotropic media in terms of radial closure along the entire length of the cavity, with specific attention given to the near-face region. The results presented are obtained from a parametric study based on full three-dimensional finite element analyses. The data are benchmarked using existing field data from the Darlington Intake Tunnel in Southern Ontario. The results of the study are then used for developing a simple expression and charts for predicting wall displacements along the entire length of a tunnel subjected to different in-situ stress conditions.

KEYWORDS: Deep tunnels, horizontal stresses, finite element, isotropic elasticity, convergence, anisotropic.

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