FINITE ELEMENT MODELING AND STRUCTURAL BEHAVIOR OF CONCRETE TUNNEL LININGS.

摘要

An improved understanding of the structural behavior of concrete tunnel linings is obtained through a series of numerical analyses of the ground-lining interaction problem with emphasis on nonlinear lining behavior. A rational analysis approach is recommended for linings in rock and soil that will include the nonlinear effects and interaction in a realistic manner. For numerical analysis, a nonlinear finite element computer program was developed to perform parametric studies to investigate a wide range of the key variables and determine how they affect the design.;Different analysis methods, closed form or numerical analysis, were compared to come up with a rational analysis approach. The performance of different finite element models and their applicability to specific situations have been investigated with consideration to the various interaction components and the way the ground loads reach the final lining. In the finite elements models the lining is represented by beam elements that can account for the nonlinear behavior of the concrete and the reinforcing steel, if present and can include the nonlinearity due to geometry change if deformations are large. The medium can be represented by radial and tangential springs with linear or nonlinear properties, or it can be represented by two-dimensional elastic isoparametric continuum elements. Also in the latter representation an interface element developed for this study can be included between the lining and the medium that has failure conditions defined by the cohesion and angle of internal friction, and elastoplastic stress-strain properties. In the recommended analysis for linings in rock, the beam-spring is suggested for use with loosening rock loads. For linings in soft ground, the excavation loading and a linear analysis is suggested for which available closed form solution could be used or a beam-continuum model is also appropriate. For some creep sensitive soils with low cohesion, fissures or other discontinuities, if the designer feels that a loosening load might occur, the lining should be checked for such loading using a beam-spring model.