Browsing by Author "Gunatilaka, IRP"

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item: Conference-Full-text
Influence of linings on stress and deformation in rock around tunnels
(2000) Puswewala, UGA; Gunatilaka, IRP; Hapuarachchi, CL; Nandasena, RM
Stress distribution and deformation in rock around lined tunnel openings subjected to internal pressure are investigated by using plane strain finite element analysis. Two typical tunnel cross- sections, in the forms of an elliptical and a horse-shoe shaped tunnel, are considered with varying thicknesses of concrete linings; material behavior is assumed to be isotropic linear elastic, and analyses are done using typical elastic material parameters to represent a particular type of rock and the concrete. Variation of major and minor principal stresses in the rock medium with increasing liner thickness and distance from the tunnel face is presented for both tunnel shapes. The influence of the lining thickness on the deformation (displacement) characteristics at selected locations in the rock medium is illustrated. The results show the general trend that stresses and deformations in the rock medium decrease with increasing liner thickness, but the effect of the liner thickness depends on the stress or displacement quantity being investigated as well as the shape of the tunnel. Thus an optimal liner thickness has to be estimated as a compromise between economy and effectiveness.
item: Thesis-Full-text
Influence of linings on stress and deformation in rock around elliptical tunnels
(2014-08-01) Gunatilaka, IRP; Puswewala, UGA
Stress and deformation behavior in rock surrounding elliptical tunnels with concrete liners is investigated by finite element analysis. The loading condition is limited to hydrostatic pressure applied inside the tunnel and it is assumed that the constitutive behaviors of both rock and concrete are according to isotropic linear elasticity. Plain strain conditions are assumed to prevail for the tunnels, which is the case when tunnels with straight axis in uniform rock media are considered. Three elliptical tunnel geometries with major to minor axis ratios of 1.156, 1.358 and 1.500 are considered for the study. Each problem geometry was analysed for liner thickness varying from 0.0 m (unlined case) to 1.0 m in steps of 0.2 m, assuming that the Young's Modulus for rock is 1/10th of that of concrete. The result for stress and deformation are presented for the rock domain, both in tabular and graphical forms. These numerical results illustrate the effect of concrete liner thickness and tunnel geometry on stress and deformation in rock. A limited parametric study is conducted by varying the Young's Modulus of rock for a selected tunnel geometry with a concrete liner thickness of 0.2 m. The present research makes a significant contribution to tunnel engineers, providing numerical tools to arrive at an optimum tunnel geometry and liner thickness, by striking a balance between cost and efficiency.