SUMMARYThe aim of this note is to quantify the in#uence of soil structure on the compression behaviour of natural soils using the disturbed state concept (DSC). The behaviour of the fully adjusted state is chosen to be that of the corresponding soil in a reconstituted condition so that the disturbance function is a direct measure of the e!ects of soil structure. A new DSC compression model is proposed. This model is able to describe the compression behaviour of structured soils under loading, swelling and reloading. Special versions of the proposed model are also described for situations (a) where the compression behaviour of the corresponding reconstituted soils is linear in the e}ln p space and (b) where the compression is one-dimensional. The ability of the proposed model and its various versions to describe the compression behaviour of structured soils has been veri"ed.
SUMMARYThis paper describes the development of a boundary element analysis for the behaviour of single piles and pile groups subjected to general three-dimensional loading and to vertical and lateral ground movements. Each pile is discretized into a series of cylindrical elements, each of which is divided into several subelements. Compatibility of vertical, lateral and rotational movements is imposed in order to obtain the necessary equations for the pile response. Via hierarchical structures, 12 non-zero sub-matrices in a global matrix are derived for the basic in#uence factors.Solutions are presented for a series of cases involving single piles and pile groups. In each case, the solutions are compared with those from more simpli"ed existing pile analyses such as those developed by Randolph and by Poulos. It is shown that for direct loading e!ects (e.g. the settlement of piles due to vertical loading), the simpli"ed analyses work well. However, for &o!-line' response (such as the lateral movement due to vertical loading) the di!erences are greater, and it is believed that the present analysis gives more reliable estimates.
This paper investigates the ground deformation characteristics induced by mechanized shield twin tunnelling along curved alignments by adopting the nonlinear three-dimensional (3D) finite element method (FEM). The performance of the adopted FEM is demonstrated to be satisfactory by comparing the numerical analysis results with the field monitoring data in a typical case history and with the predicted results generated by a modified version of the Peck’s empirical Gaussian formula. It has been found that the tunnelling-induced transverse ground surface settlement troughs and the distributions of the subsurface horizontal and vertical ground displacements are mostly similar in both form and magnitude for the considered various radii of curvature of tunnel alignment including 50 m, 100 m, 150 m, 200 m, 250 m, 300 m, 400 m, and infinity (i.e., straight-line tunnel). Considering the variational characteristics of the ground deformations with the magnitude of the radius of curvature, the radius of curvature of 100 m can be regarded as a critical tunnel alignment radius of curvature controlling the transformation of the curved tunnelling-induced ground deformational behaviors. For the benefit of geotechnical engineers interested in curved tunnelling with a small radius of curvature, a discussion of the technologies for reducing the overexcavation and improving the accuracy of tunnel lining segment installation is also presented.
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