In geotechnical engineering practice, the increase over time of pile capacity after installation is sometimes referred to as pile setup or freeze. Pile setup, which is often associated with piles driven into saturated clays and silts, is mainly attributed to soil consolidation around the pile. Field observations have shown that pile setup is significant and continues to develop for a long time after pile installation. Pile foundations are usually expensive. Therefore, taking a small percentage of pile setup into consideration will result in cost reduction and savings in piling projects. This paper presents a general numerical procedure to predict pile setup by simulating the behavior of the pile during its different life stages: installation, subsequent consolidation, and loading. The Hierarchical Single Surface modeling approach, the strain path method, and the nonlinear finite element analysis of porous media were used in the analyses. The procedure was verified by successfully predicting the field behavior of pile segment models installed into soft marine clay. Numerical experiments were also conducted to demonstrate the applicability of the numerical procedure to full-scale driven piles. Piles with diameters of 0.3 m and 0.5 m and a length of 10 m were considered in the analyses.
SUMMARYHierarchical single surface (HISS) 6, and 6, models are briefly discussed. An algorithm for the implementation of 6, and 6, models in a finite element code and the associated subroutines, written in FORTRAN 77, are presented. The algorithm is general and can be adopted for other computer codes with minor changes. Detailed steps and subroutines are included for easy implementation of the models in specific codes. Two example problems are also presented to enable the user to verify the implementation.
SUMMARYSuccessful numerical simulation of geosynthetic-reinforced earth structures depends on selecting proper constitutive models for soils, geosynthetics and soil}geosynthetic interfaces. Many constitutive models are available for modelling soils and geosynthetics. However, constitutive models for soil}geosynthetic interfaces which can capture most of the important characteristics of interface response are not readily available. In this paper, an elasto-plastic constitutive model based on the disturbed state concept (DSC) for geosynthetic}soil interfaces has been presented. The proposed model is capable of capturing most of the important characteristics of interface response, such as dilation, hardening and softening. The behaviour of interfaces under the direct shear test has been predicted by the model. The present model has been implemented in the "nite element procedure in association with the thin-layer element. Five pull-out tests with two di!erent geogrids have been simulated numerically using FEM. For the calibration of the constitutive models used in FEM, the standard laboratory tests used are: (1) triaxial tests for the sand, (2) direct shear tests for the interfaces and (3) axial tension tests for the geogrids. The results of the "nite element simulations of pull-out tests agree well with the test data. The proposed model can be used for the stress-deformation study of geosynthetic-reinforced embankments through numerical simulation.
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