ABSTRACT:

In this paper an attempt has been made to simplify the complex interface pullout mechanism using nonlinear elastic formulations. Formulations of interface pullout tests are expressed in non-dimensional terms for general applicability. Concepts of relative stiffness and displacement parameters are defined to explain the non-linear pullout response. Comparative parametric studies were carried out for a range of relative stiffness and bond resistance. Normalised load - displacement relations and the variations of pullout force and displacements with distance, are expressed in finite difference equations and solutions presented graphically. The predictions based upon a hyperbolic relation for shear mobilisation are compared with those from the elasto-plastic model. It was observed that the formulations might be used for small to large strain problems i.e., for inextensible to extensible reinforcements. Evaluated results of laboratory and field pullout experiments for steel straps, geotextiles, polymers and nylon geosynthetics are summarised.

INTRODUCTION

Earth reinforcements are increasingly used in offshore/harbour structures, retaining walls, embankments, landfills, liners, foundations, in-situ slopes, excavations and road construction. New developments in the innovative use of geosynthetics have offered engineered solutions for reinforcement, drainage, separation and stabilisation. This has resulted in the applications of the theory to practice of numerous earth structures, such as slopes and embankments, retaining walls, foundations and dams. There have been many hypotheses postulated about the load transfer and interaction mechanisms but none fully explain the phenomena. Major applications of reinforced soil are retaining walls and steep slopes where the reinforcement provides short term as well as long term stability over the design life of the reinforced soil structures. Figure 1 illustrates typical examples of reinforced soils.

FORMULATIONS REVIEWS

To understand the behaviour of reinforced earth various laboratory tests such as triaxial, direct shear, pull-out and physical model tests were investigated and used by many researchers.

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