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In this study, in situ experiments were conducted to study the changing characteristics of the lateral and longitudinal resistance of a ballast bed, and a three-dimensional model for the ballast bed and sleeper was constructed based on the discrete-element method. The effects of the lateral and longitudinal resistance of the ballast bed, such as gravel ballast grading, sleeper depth, the angle of the shoulder slope, and ballast bed shoulder width, among others, were studied. The results suggest that (1) the lateral and longitudinal resistance of the ballast bed increases with the widening of ballast grading, and within the size distribution limits, the resistance of the ballast bed satisfies the specification; (2) the lateral and longitudinal resistance of ballast bed increases with an increase in the sleeper depth and the resistance of ballast bed satisfies the specifications for sleeper depth greater than 150 mm; (3) the lateral resistance of the ballast bed increases with a decrease in the angle of the shoulder slope, whereas the longitudinal resistance remains unchanged and the resistance of the ballast bed satisfies the specifications for slope gradient of 1:1.75 or less; and finally, (4) the lateral resistance of the ballast bed increases with the widening of the ballast bed shoulder, whereas the longitudinal resistance remains unchanged, and the resistance of ballast bed satisfies the specifications when the shoulder width is greater than 400 mm.

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SUMMARYThis paper presents a coupled, elastoplastic, finite element and boundary element method for the twodimensional, non-linear analysis of anisotropic jointed rock. The non-linear and anisotropic behaviour of a jointed rock mass is simulated by representing the mass as an equivalent anisotropic, elastoplastic continuum, so that the influence of the jointing system is 'smeared' across the continuum, i.e. the individual joints are not modelled as discrete entities. Numerical examples have been solved to verify the capability, accuracy and efficiency of the present technique. The proposed technique has also been applied to the analysis of tunnel excavation problems in plane strain. The effects of anisotropy and non-linearity of the jointed rock mass during excavation have been investigated in some detail.

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