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Analytical and numerical solutions for the problem of geosynthetic-reinforced fills over a void have been the subject of investigation for the last four decades. A common feature of this prior work is that all methods have treated the analytical solutions as deterministic. While the treatment of some input parameters must be taken as deterministic, there are other parameters that have uncertainty. Furthermore, the underlying mechanistic models for load and resistance terms in the limit state equations for the reinforced fill over a void problem can be expected to have different accuracy. This paper revisits the problem of geosynthetic-reinforced fills over voids from a probabilistic point of view for reinforcement tensile strain, tensile strength, and geosynthetic stiffness limit states. Particular attention is paid to the method used to select the isochronous stiffness of the reinforcement and the associated uncertainty in the magnitude of that value. The paper demonstrates how the factor of safety from deterministic past practice can be linked quantitatively to the reliability index used in contemporary probabilistic design. Finally, the paper demonstrates the advantage of using product-specific constant-load creep test results to maximise margins of safety for strength and stiffness limit states in both deterministic and probabilistic frameworks. [ABSTRACT FROM AUTHOR]

The role of temperature and relative humidity in long-term mechanical and chemical degradation of polyester fibres due to hydrolysis and creep is well documented. This study presents the results of a thermo-hydraulic 2D finite-element model used to estimate the magnitude and distribution of in situ temperature, relative humidity, and degree of saturation in the backfill of reinforced soil walls (RSWs) due to changes in atmospheric boundary conditions. Boundary conditions for in-air temperature, relative humidity and daily precipitation were taken from weather databases for continental, Mediterranean, desert, and tropical climates. Scenarios with different water tables, and permeable or impermeable zones around the reinforced soil zone were analyzed. Numerical outcomes show that mean in-soil temperature values can be related to the mean annual atmospheric value for each geographical location, with relevant fluctuations limited to the first 3 m of distance from the vertical and horizontal boundaries. In-soil relative humidity values depended on the climate dataset and the permeability of the zones adjacent to the reinforced soil. The results of this study and lessons learned are a valuable precursor for future studies of coupled thermo-hydro-mechanical modelling of polyester geosynthetic RSWs under in situ operational conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT: This paper reports the results of three 4 m high full-scale instrumented geogrid-reinforced soil walls constructed with different structural facings having a range of stiffness. The walls were seated on a 2 m deep foundation layer that was laterally supported at the base of the wall face by a rigid bulkhead. Following end of construction, the bulkhead was moved outward in stages to simulate loss of foundation support in the vicinity of the wall toe. Bulkhead loads, wall deformations, backfill settlements, reinforcement loads and earth pressures recorded at end of construction and during bulkhead displacement are presented in this paper. Measured reinforcement loads are compared to predicted loads at end of construction using different design methods. The walls demonstrated that there was available reserve load capacity which prevented internal failure mechanisms from developing in the reinforced soil zone even after significant loss of foundation support in the vicinity of the wall toe. At the end of each test the reinforcement layers were shortened in stages by cutting using nichrome heating wires. For the most flexible wall in this programme, the shortening of the reinforcement triggered a composite soil failure mechanism extending from the base of the foundation zone to the surface of the soil backfill. Implications of the analysis results and other observations on wall performance and design are discussed. [ABSTRACT FROM AUTHOR]

The articles announces the best "Geosynthetics International" papers for 2008 and 2009 which includes "Geotextile Containment for Hydraulic and Environmental Engineering," by C. R. Lawson, "Leachate Chemical Composition Effects on OIT Depletion in an HDPE Geomembrane," by R. K. Rowe and colleagues, and "New Direction for Earth Reinforcement: Disaster Prevention for Earthfill Dams," by Y. Mohri and colleagues.