Influence of deformable geofoam bufers on the static and dynamic behaviors of cantilever retaining walls

Download
2011
Ertuğrul, Özgür Lütfi
Static and dynamic interaction mechanism of the retained soil-compressible geofoam buffer and yielding retaining structures requires further investigation. The present study, initiated on this motive, discusses the results of 1-g physical model tests and numerical analyses of cantilever retaining walls with and without deformable geofoam buffers between the wall and cohesionless granular backfill. 0.7m high walls with various wall thicknesses were utilized in the physical modeling. Dynamic tests were carried out by using a laminar container placed on a uni-axial shaking table. Influence of buffer thickness, geofoam type and wall flexibility as well as base excitation characteristics on the lateral earth pressures and flexural wall deflections were under concern. Outcomes of the analyses performed with FLAC-2D (v6.0) finite difference code were validated against the results of the physical model tests. It was observed that the arching effect induced in the retained soil by the lateral compression of the lower half of the geofoam buffer has a positive effect, as this zone is able to absorb a portion of the total unbalanced lateral force exerted by the backfill thus causing a reduction in the static and seismic lateral wall pressures. Relative thickness and stiffness of the geofoam buffer appear to be the most dominant factors affecting the reduction in earth thrust. Lateral earth pressure coefficients determined from physical model tests were compared with those calculated using methods available in the literature. Good agreement was observed between the predictions. Graphs were provided to estimate the static and dynamic lateral earth pressure coefficients for various combinations of wall stiffness and buffer characteristics. Analysis of a 6m high prototype cantilever wall subjected to an excitation recorded in August 17, 1999 Kocaeli earthquake by finite difference method exhibited the contribution of geofoam buffers on seismic performance of cantilever earth retaining walls. It was observed that the presence of an EPS geofoam inclusion provides a reduction of the permanent flexural wall deflections as well as total seismic thrust likely to be experienced by the wall during an earthquake.

Suggestions

Influence of EPS Geofoam Buffers on the Static Behavior of Cantilever Earth-Retaining Walls
Ertugrul, Ozgur L.; Ozkan, M. Yener (LookUs Bilisim A.S., 2012)
In this study, the effect of expanded polystyrene (EPS) buffers on lateral stresses and deflections of model retaining walls with various flexibility values were investigated. For this purpose, 0.7 m high model walls were instrumented and 1-g model tests were performed in laboratory environment. In the first group of tests, the wall models retain only granular cohesionless backfill whereas in the second and third group of tests, EPS deformable buffers of two different thicknesses were installed between ...
Comparison of factor of safety obtained from limit equilibrium methods with strength reduction factors in finite element modeling
Engin, Volkan; Toker, Nabi Kartal; Erol, Orhan; Department of Civil Engineering (2012)
Designing with Limit Equilibrium Methods involve a factor of safety (FS) in order to maintain the stability and to keep the resisting structure away from limit state on the safe side. Finite Element Program (such as Plaxis) on the other hand, instead of an FS, reduces the shear strength of the soil by introducing a reduction factor that is applied to tanɸ & c values, resulting in different analysis results compared with Limit Equilibrium Methods results. This study aims to associate tanɸ & c reduction facto...
Comparison of safety factors obtained from limit equilibrium methods and finite element analyses
Engin, Volkan; Toker, Nabi Kartal (2012-06-30)
Designing with limit equilibrium methods involves a factor of safety as a measure of stability, i.e. how far the resisting structure is from the limit state, on the safe side. On the other hand, current engineering practice employs finite element programs (such as PLAXIS) which, instead of using a conventionally-defined factor of safety, reduces the overall shear strength of the soil by introducing a reduction factor that is applied to soil strength (i.e. tan  and c values). Such fundamental differences in...
An integrated approach to computational vision - The edge strength function and the nested symmetries
Tarı, Zehra Sibel (1999-01-01)
A new development in local symmetry extraction and its connections to segmentation functionals and the fronts propagating with curvature-dependent speed are examined. The basic tool is a new distance function that attains its maximum value at the shape boundary and decays rapidly away from there. It is shown that the Hessian of the distance function captures perceptual information that can be extracted easily, efficiently, and robustly in the form of nested local shape symmetries at multiple scales. The mos...
Assessment of Transient Stability of Nonlinear Dynamic Systems by the Method of Tangent Hyperplanes and the Method of Tangent Hypersurfaces
Eskicioglu, Ahmet M. (ASME International, 1989-9-1)
Two direct methods, the method of tangent hyperplanes and the method of tangent hypersurfaces, are applied to an elementary nonlinear dynamic system for transient stability assessment. The former method is based on the approximation of the asymptotic stability boundary by hyperplanes at a certain class of unstable singular points in the state-space, and the latter replaces hyperplanes by hypersurfaces. The applicability and accuracy of both methods are evaluated through a comparison of results.
Citation Formats
Ö. L. Ertuğrul, “Influence of deformable geofoam bufers on the static and dynamic behaviors of cantilever retaining walls,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.