Permanent Deformation Analysis on Various Base Materials under Accelerated Pavement Testing

Numerous studies have revealed the benefits of using geogrids in a flexible pavement, especially for reducing permanent deformation. One of the questions that remain about the effectiveness of a geogrid in reinforcing of pavement is the extent to which the geogrid is engaged and mobilized throughout its service. This paper presents results of a laboratory study on various geogrid products embedded in flexible-pavement sections. The laboratory-scale pavement sections were subjected to cyclic moving wheel loads by using reduced-scale accelerated pavement testing (APT). During the APT, strains that developed in the geogrids were measured at intervals of loading applications by strain gauges installed in pairs on the upper and lower surfaces of the geogrid ribs. Permanent deformation of the subgrade was also measured at the same intervals of loading applications. The measurements of geogrid strains throughout the construction process indicated that the construction resulted in a considerable prestressing effect on the geogrids. Measurements from the individual strain gauges in pairs showed that the gauges installed on the upper surfaces of the ribs were in compression while those on the lower surfaces were in tension; the situation suggested a significant effect on the flexural deflection of the ribs on the tensile strain measurements from the strain gauges. Furthermore, it was observed that geogrid ribs in the longitudinal direction of traffic loading were not mobilized, while considerable strains were developed in geogrid ribs in the direction transverse to traffic loading. A clear correlation was found between the reinforcing forces developed in the geogrids and the performance of the reinforced subgrade in relation to resisting permanent deformation.

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Measuring Pavement Permanent Deformation in Accelerated Pavement Testing

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120915471 ◽

2020 ◽

Vol 2674 (5) ◽

pp. 340-348 ◽

Cited By ~ 1

Author(s):

Wenjing Xue ◽

Gerardo W. Flintsch ◽

Brian K. Diefenderfer

Keyword(s):

Surface Deformation ◽

Permanent Deformation ◽

Practical Method ◽

Virginia Tech ◽

Pavement Performance ◽

Forensic Investigation ◽

Accelerated Pavement Testing ◽

Pavement Materials ◽

Pavement Structure ◽

Pavement Testing

Permanent deformation is an essential criterion for evaluating pavement performance. In an accelerated pavement testing (APT) experiment at the Virginia Tech Transportation Institute, a laser profiler, multi-depth deflectometer (MDD), and forensic investigation were used to measure the permanent deformation of a pavement system. This paper analyzes the permanent deformation measured via the three methods during the APT experiment. The major concern among the three methods is applicability rather than accuracy. To measure surface deformation, the laser profiler is a more practical method than MDD in APT, as it can scan the whole surface instead of just one point. To measure the deformation within a pavement structure, MDD provides deformation development throughout the whole experiment, which is helpful for a deeper understanding of pavement materials and structures. However, MDD is also more expensive and requires significant installation effort and maintenance during the experiment compared with forensic investigation, which also needs to be considered.

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Accelerated Pavement Testing to Evaluate the Reinforcement Effect of Geogrids in Flexible Pavements

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198120935120 ◽

2020 ◽

Vol 2674 (10) ◽

pp. 134-145

Author(s):

Bingye Han ◽

Pawel Polaczyk ◽

Hongren Gong ◽

Rong Ma ◽

Yuetan Ma ◽

...

Keyword(s):

Permanent Deformation ◽

Flexible Pavements ◽

Performance Testing ◽

Base Layer ◽

Reinforcement Effect ◽

Accelerated Pavement Testing ◽

Forensic Evaluations ◽

Base Course ◽

Pavement Testing ◽

Response Testing

This study presents an accelerated pavement testing (APT) to evaluate the reinforcement effect of geogrids in flexible pavements. A full-scale conventional three-layer flexible pavement structure was constructed, and was divided into one unreinforced section and two reinforced sections with base reinforced by geogrids placed at different depth of base course. The testing program was divided into three parts: performance testing, response testing, and forensic evaluations. The performance testing recorded the development of surface permanent deformation with the number of loadings. The falling weight deflectometer (FWD) was employed to investigate deflections and moduli of flexible pavements in the response testing. The excavation of pavements was to further analyze reinforcement mechanisms. Test results demonstrated the benefits of incorporating geogrids in base course in reducing the permanent deformation and improving the modulus of base course. Compared with the unreinforced section, accumulated permanent deformations in the two reinforced sections decreased significantly, with a drop of 13%–37%, and the back-calculated moduli of the reinforced base increased by 58%–78% after APT. It was possible that sufficient permanent deformation was needed for mobilizing geogrids to constrain lateral movements of granular particles, to increase the overall structural behavior of the reinforced base course, and to improve the stress distribution on the subgrade. These interaction mechanisms were also confirmed in the pavement trench. For a pavement system consisting of a thin surface and base layer, the proper placement position of geogrids was at the base–subgrade interface for this test and loading arrangement.

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