Performance of an 11 m high block-faced geogrid wall designed using the K-stiffness method

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.

3D modelling of strip reinforced MSE walls

“…Hence, the quantitative outcomes reported here must be appreciated in relative terms. Examples of the significant influence of construction technique on facing alignment can be found in the papers by Allen and Bathurst [4] for an 11-m-high modular block wall reinforced with geogrids and a steel strip reinforced 17-m-high incremental concrete panel wall reported by Runser [44] and Runser et al [45]. Numerical modelling of these walls by Yu et al [52] and Damians et al [21] was not able to explicitly account for the effects of documented construction issues in their numerical simulations.…”

Nonlinear load–strain modeling of polypropylene geogrids during constant rate‐of‐strain loading

“…Hence, average strain rates during construction can be computed to be in the range of 1 × 10 −4 % strain/min to 1 × 10 −5 % strain/min. In a more recent case of an instrumented field wall constructed with a HDPE uniaxial geogrid, a maximum average strain rate of about 1 × 10 −4 % strain/min can be deduced from strain measurements . These strain rates are five to six orders of magnitude less than a conventional test performed at 10% strain/min according to the ASTM: D6637‐11 method of test.…”

“…Predicted and measured load–strain–time measurements for the same PP used in the pullout box test program mentioned above are compared using both models. The first model uses a hyperbolic expression with the general form reported in earlier articles by Hatami and Bathurst and Allen and Bathurst but has been modified to explicitly include the influence of strain‐rate on load–strain response of the PP geogrid material under monotonic and stepped constant rate‐of‐strain testing. Hyperbolic models have also been used in geomechanics problems to model interfaces , soil reinforcement pullout , and triaxial compression tests on soil .…”

Benefits of geosynthetic reinforcement in widening of embankments subjected to foundation differential settlement

“…The calibration factor of the geogrid was 1.0, based on the strain gauge measurement on the geogrid when the global strain was smaller than 3%, and would be 1.05 when the global strain of the geogrid was 4%. Allen and Bathurst (2014) reported the calibration factors for high-density polyethylene geogrids ranging from 1.0 to 1.7 (the stiffer geogrid had a lower factor). Based on the test results, the average tensile stiffness of the geogrid used in the physical model test was approximately 500 kN/m.…”

“…Geosynthetic reinforcement including geogrids, woven geotextiles, and geocells have been used for roads (Berg et al 2000;Han et al 2011), walls (Bathurst et al 2002;Leshchinsky and Han 2004;Huang et al 2009a;Allen and Bathurst 2014) and embankments (Han and Gabr 2002). Li and Gong (2001) used geogrids with gravel cushions to enhance the integrity of the existing and widened portions of the embankment.…”