Abstract
Initiating at the small-strain shear modulus (Gmax), the mechanical nonlinear stress-strain-strength behavior of soil manifests in the form of modulus reduction, typically expressed in normalized form as Gop/Gmax. Here, Gopis the operative shear modulus – a reduced stiffness value corresponding to strain levels that the soil is experiencing. Assessment of Gopis critical to reliable predictions of load-related deformations within the soil. Among the various categories of loading, deep foundations and pilings exhibit a typical mechanism of axial load transfer to the foundation soil. For friction type piles, the stiffness reduction mostly takes place along the pile shaft-soil interface. Within the framework of an analytical solution, the back analyses from the results of load tests on pile foundations, together with the knowledge of pile geometries and soil parameters, provide an outline for evaluation of Gopat different load increments. This paper explains the methodology employed to develop stiffness reduction curves (Gop/Gmax) as a function of pseudo-strain (γp = wt/d), where, wt= settlement at the pile top, and d = pile diameter. Algorithms that integrate the plasticity characteristics of the soil are also presented. The results afford an improved evaluation of the complete nonlinear load-settlement (Q-wt) response for pile foundations under axial loads.
Highlights
The relevance of the small-strain stiffness of soils, as represented by Gmax, has been a common thread in many research studies over the past three decades [1, 2]
Among the various categories of loading, deep foundations in the form of piles exhibit a typical mechanism of static axial load transfer to the foundation geomaterials
This paper summarizes a methodology employed by the authors in generating a new family of shear modulus reduction schemes meant for use in pile foundations along with an overview of the database employed for this purpose
Summary
The relevance of the small-strain stiffness of soils, as represented by Gmax, has been a common thread in many research studies over the past three decades [1, 2]. Having an appropriate modulus reduction scheme that accounts for important geomaterial parameters, pile geometry, and relevant pile typology (as related to the method of installation that inherently accounts for pile interaction with the surrounding geomaterials along the shaft interface) offers convenience in improved assessment of this load-settlement (Q-w) response. Such a model can be developed via a semi-empirical approach of integrating field data with a rational analytical solution. A new graphical model with its associated algorithms are presented together with a flowchart for its implementation in predicting the nonlinear axial Q-w response of single pile foundations
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