Citation

Allen TM, Bathurst RJ. Can. Geotech. J. 2014; 51(1): 16-29.

Copyright

(Copyright © 2014, National Research Council of Canada)

DOI

10.1139/cgj-2013-0261

PMID

unavailable

Abstract

An 11 m high dry-stacked masonry concrete block wall reinforced with a high-density polyethylene (HDPE) geogrid was designed, instrumented, and monitored for a period of 2 years as part of a highway-widening project southeast of Seattle, Washington, in the USA. An extensive materials-testing program was conducted to characterize the geogrid and backfill soil properties. The empirical-based K-stiffness method was used to design the wall, and this approach resulted in a 35% reduction in total required reinforcement strength compared with the American Association of State Highway and Transportation Officials / Federal Highway Administration (AASHTO/FHWA) simplified method. The cost savings more than compensated for the cost of the instrumentation program. Geogrid strains were measured using strain gauges and extensometers, and the walls were surveyed to monitor facing deformations. The stiffness of the geogrid materials was computed from the results of laboratory in-isolation constant-load (creep) tests. The time- and strain-dependent stiffness values, in combination with measured strains, were used to compute measured reinforcement loads at the reinforcement connections and at locations within the reinforced soil backfill. The measured loads were compared with class A, B, and C1 predictions using the AASHTO/FHWA simplified and K-stiffness methods. These comparisons demonstrate that the simplified method significantly overestimated reinforcement loads, whereas the K-stiffness method provided estimates that were judged to be in better agreement with the measured results. The paper also quantifies the influence of construction procedures on reinforcement strains and load, shows that long-term creep of the reinforcement after 2 years after construction is negligible, and identifies lessons learned.

KEYWORDS: geosynthetics, walls, stresses, strains, design, soil reinforcement, simplified method, K-stiffness method, hyperbolic isochronous model

Un mur en maçonnerie de 11 mètres de haut, fait de blocs de béton placés sec et renforcé d'une géogrille en polyéthylène de haute densité (HDPE), a été conçu, instrumenté et suivi sur une période de 2 ans. Ce mur faisait partie d'un projet d'élargissement d'une autoroute au sud-est de Seattle, Washington, aux États-Unis. Un vaste programme d'essais sur les matériaux a été réalisé afin de caractériser les propriétés de la géogrille et du sol de remblayage. La méthode de rigidité K, basée sur des lois empiriques, a été utilisée pour concevoir le mur et cette approche a permis de réduire de 35 % la résistance en renforcement totale requise comparativement à celle requise selon la méthode simplifiée de l'American Association of State Highway and Transportation Officials / Federal Highway Administration (AASHTO/FHWA). Les économies en argent ont plus que compensé pour le coût du programme d'instrumentation. Les déformations de la géogrille ont été mesurées à l'aide de jauges de déformation et d'extensomètres,...