International Journal of Geomechanics

In this work, we present the solutions for displacements and stresses along the centerline of a uniform vertical circular load in an inhomogeneous cross-anisotropic half-space with its Young’s and shear moduli varying exponentially with depth. The planes of cross anisotropy are assumed to be parallel to the horizontal surface. The presented solutions can be directly integrated from the point load solution in a cylindrical coordinate system, which were derived by the writers. However, the resulting integrals of the circular solution for displacements and stresses cannot be given in closed form; hence, numerical integrations are required. For a homogeneous cross-anisotropic half-space, the numerical results agree very well with the exact solutions of Hanson and Puja, published in 1996. Two examples are given to elucidate the effect of inhomogeneity, and the type and degree of soil anisotropy on the vertical displacement and vertical normal stress in the inhomogeneous isotropic/cross-anisotropic soils subjected to a uniform vertical circular load acting on the surface. The proposed solutions can more realistically simulate the actual stratum of loading problem in many areas of engineering practice.

This paper presents an analytical investigation of the ability of friction sleeves of varying lengths to reliably identify layer interfaces and stratigraphic anomalies within the subsurface. Analytical and parametric analyses were performed using synthetic sleeve $fs$ profiles that are statistically equivalent to piezocone penetration test $fs$ profiles, thereby enabling study of realistic profiles with known statistical properties. This approach demonstrates that the standard friction sleeve lengths can cause incorrect interpretations of the location of distinct interfaces and of the sleeve friction measurements near this interface. The study also shows that the vertical extent of thin anomalies can be overestimated and the frictional characteristics of the soil within the anomaly can be incorrectly interpreted if the length of the friction sleeve relative to the thickness of the anomaly is not considered.

This paper studies the advantages of geocell reinforcement on the performance of earth embankments constructed over weak foundation soil through laboratory model tests and proposes a simple method for the design of geocell-supported embankments. Model embankments were constructed above a layer of geocells formed using geogrids on top of a soft clay bed prepared in a steel test tank. Uniform surcharge pressure was applied on the crest and pressure-deformation behavior of the embankment and strains in the walls of geocells were monitored continuously until the failure was reached. The influence on the behavior of the embankment of various parameters—like tensile stiffness of geocell material, height and length of geocell layer, pocket-size of the cell, pattern of formation of geocells, and type of fill material inside the cells—was studied. Geocell reinforcement was found to be advantageous in increasing the load-bearing capacity and reducing the deformations of the embankments. The experimental results were validated using a general purpose slope-stability program and a design procedure useful for the preliminary design of geocell-supported embankments is illustrated.

This study is concerned with the constitutive modeling of asphalt concrete. Unlike most constitutive models for asphalt concrete that do not take into account the evolution of the microstructure of the material, this study incorporates the evolution of the microstructure by using a framework that recognizes that a body’s natural configurations can evolve as the microstructure changes. The general framework, on which this study is based, is cast within a full thermomechanical setting. In this paper, we develop models within the context of a mechanical framework that stems from the general framework for models based on the full thermodynamic framework and the resulting equations represent a nonlinear rate type viscoelastic model. The creep and stress relaxation experiments of Monismith and Secor are used for validating the efficacy of the model, and it is found that the predictions of the theory agree very well with the available experimental results. The advantages of using such a framework are many, especially when one wants to model the diverse mechanical and thermodynamic response characteristics of asphalt and asphalt concrete.

This paper addresses the problem of a circular footing of finite but nonzero stiffness embedded in an isotropic nonhomogeneous elastic half-space. The problem is solved by coupling the scaled boundary finite-element method with axisymmetric shell finite elements. The coupling of the two methods is validated by comparing computed solutions with analytical solutions for a flexible footing subjected to a uniformly distributed vertical load embedded in an elastic full-space. Based on the finding that the bending stiffness of the footing dictates the response for vertical and moment load cases, whereas the normal stiffness of the footing dominates the horizontal response, a convenient method for estimating dimensionless elastic stiffness coefficients is presented graphically. New results are presented for homogeneous and Gibson soil profiles and Poisson’s ratios of 0.2 and 0.499, to represent both sand and clay. An example demonstrating a practical application of these results is also provided.

The effect of principal stress rotation on the mechanical behavior of Kaolin clay is investigated using combined axial-torsional tests on hollow cylindrical specimens. The yielding behavior and failure criteria are found to be strongly dependent on the principal stress rotation angle $\left(\beta \right)$ and plastic work. A unique plastic potential function determined solely by the current stress state is not sufficient to model the plastic flow observed in these experiments. Therefore, a single hardening elasto-plastic model that includes a loading-history-dependent plastic potential function is proposed for normally consolidated Kaolin clay subjected to principal stress rotation. A general methodology for incorporating history dependency in modeling complex elasto-plastic behavior of cohesive soils is presented along with comparisons of model predictions with experimental data.

Since the planes of foundations are not usually regularly shaped, and the loads are often applied on the anisotropic materials, such as transversely isotropic soils or rocks, calculating the induced displacements and stresses by an arbitrarily shaped load for a transversely isotropic medium is rather tedious and time consuming. Hence, how to estimate those values correctly and quickly by computer was the major objective in constructing the fast anisotropic displacements and stresses (FADAS). FADAS is based on the solutions of displacements and stresses in a transversely isotropic half space subjected to three-dimensional buried right-angled triangular loads, which were derived by the first writer. Utilizing these solutions, the displacements and stresses for a general triangular region at any point can be obtained by superposition. An illustrative example is given to demonstrate a few features of FADAS, and to elucidate how to compute the vertical displacement induced by a uniform vertical circular load in an equivalent medium. Results from FADAS reveal that the usage of it is correct, easy, and very fast to offer a good tool for practitioners.