2013 Session: 623

• Reinforcement Tensile Behavior Under Cyclic Moving Wheel Loads
  Abstract: Numerous studies have revealed that the use of geogrids in a flexible pavement can lead to an improvement in the performance of a pavement structure, especially its resistance to permanent deformation. One of the questions that remains regarding the effectiveness of the geogrid in reinforcing the pavement is how much 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 built on soft soil subgrade. The laboratory-scale flexible pavement sections were subjected to cyclic unidirectional moving wheel loads using reduced-scale accelerated pavement testing (APT). During the accelerated pavement testing, strains developed in the geogrids were measured at intervals of loading applications by strain gages installed in pairs on the upper and lower surfaces of the geogrid ribs. Subgrade permanent deformation was also measured at the same intervals of loading applications. The tensile behavior of the various geogrids embedded in pavements were compared and examined. Based on the measurements of geogrid strains throughout the construction process, it was found that the pavement construction resulted in a considerable prestressing effect on the geogrids. Measurements from the individual strain gages in pairs show that the strain gages installed on the upper surfaces of the geogrid ribs were in compression while the gages on the lower surfaces were in tension, indicating a significant effect of ribs¡¯ flexural deflection on the tensile strain measurements from the strain gages. Furthermore, it was observed that geogrid ribs in the longitudinal direction of the traffic loading were not mobilized while considerable strains were developed in geogrid ribs in the direction transverse to the traffic loading. A clear correlation was found between the reinforcing forces developed in the geogrids and the performance of the reinforced subgrade in terms of resisting permanent deformation.
  Authors: Tang, Xiaochao; Palomino, Angelica M.; Stoffels, Shelley M.
  Authors: Tang, Xiaochao; Palomino, Angelica M.; Stoffels, Shelley M.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-0481
• Performance Assessment of Geosynthetics Versus Cement as Subgrade Stabilization Measures
  Abstract: Work in this paper presents the results of field testing on four instrumented roadway sections constructed on poor subgrade soils and stabilized with select fill, geosynthetics or cement. Loading was applied using 1000 consecutive truck passes and profile surveying was performed to provide permanent deformation (rutting) data. Peak vertical stresses at the subgrade as well as moisture conditions were also monitored. Results indicated that the deep undercut (31 inch) with select material backfill section produced the largest cumulative rut depths due shallow incremental plastic strains induced during each axle pass. The use of a thin ABC surface layer (2 to 3 inch) over the select material reduced the rate of rutting. The biaxial geogrid and the high strength geotextile showed a relatively equal performance in all aspects of the study. The cement stabilized section produced slightly larger average rut depth than the geosynthetically-reinforced sections due to localized areas of pronounced cumulative rutting. However, there were several areas of the soil-cement test section that performed as well as the geosynthetically-reinforced sections.
  Authors: Cowell, Tim; Pyo, Sangchul; Gabr, Mohammed A.; Borden, Roy H.; Kim, Kyung Jun
  Authors: Cowell, Tim; Pyo, Sangchul; Gabr, Mohammed A.; Borden, Roy H.; Kim, Kyung Jun
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-1536
• Numerical Analysis of Geocell-Reinforced Aggregate and Ballast Overlying Soft Clay Subgrade
  Abstract: Over the past several decades the geotechnical engineers have experimented with many forms of reinforcement techniques for construction of embankments, retaining walls, pavements and foundations where in geotextiles and geogrids were extensively used. Geocells is one of the recently found applications of reinforcement technique, which provides a three dimensional confinement to the infill material. Although the amount of research conducted on sand, clay and layered soil subgrades has been extensive, limited research has been conducted on the aggregates reinforced with geocells. This paper presents a study the behavior of geocell reinforcement under monotonically loaded plane strain plate on a thin layer of aggregates of size ranging from 20 to 75mm overlying soft clay subgrade. Results of a series of laboratory model tests on an unreinforced and geocell reinforced aggregate overlying soft clay subgrade prepared in a test tank of dimensions 700mmx300mmx700mm are presented. In addition to the laboratory model tests, the model tests were simulated using a finite difference code to predict the behavior of geocell reinforced aggregate. The numerical simulations are compared with the experimental results. The numerical and experimental results manifested the importance that the geocell reinforcement has a significant effect on the aggregate behavior. The results also depicted that the stiffness of underlying soft clay subgrade has a significant influence on the geocell-aggregate composite material in redistributing the loading system.
  Authors: Saride, Sireesh; Sitharam, T. G.; Puppala, Anand J.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-3057
• Performance Assessment of Geosynthetics Versus Cement as Subgrade Stabilization Measures
  Authors: Kim, Kyung
  Authors: Kim, Kyung
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-1536
• Reinforcement Tensile Behavior Under Cyclic Moving Wheel Loads
  Authors: Tang, Xiaochao
  Authors: Tang, Xiaochao
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-0481
• Numerical Analysis of Geocell-Reinforced Aggregate and Ballast Overlying Soft Clay Subgrade
  Authors: Puppala, Anand
  Authors: Puppala, Anand
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-3057
• Numerical Analysis of Geocell-Reinforced Aggregate and Ballast Overlying Soft Clay Subgrade
  Authors: Saride, Sireesh
  Authors: Saride, Sireesh
  Year: 2013
  Document Type: Presentation
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-3057
• Performance of Geogrid-Stabilized Gravel Flexible Base with Bituminous Surface Treatment
  Abstract:

  A full-sale test section was constructed and trafficked at the U.S. Army Engineer Research and Development Center (ERDC) to evaluate the performance of geogrid stabilized low-volume roads. The test section consisted of two typical low-volume “farm-to-market” lanes constructed with a double bituminous surface treatment over a crushed limestone flexible base course, meeting TxDOT criteria, and a medium subgrade support (CBR 6%). One lane was stabilized with geogrid and constructed with a 6-in. base course. The second lane was constructed with an unstabilized 8-in. base course. Each test lane contained a suite of instrumentation consisting of strain gauges, earth pressure cells, moisture probes, pore water pressure transducers, and temperature probes. The test pavements were subjected to accelerated trafficking to evaluate the relative performance of the different pavement structures. Permanent surface deformations and pavement stiffness were measured periodically throughout traffic testing. The results of the study showed that the performance of the thinner geogrid stabilized pavement section was equal to the performance of the thicker unstabilized control pavement. Results were used to develop effective base course structural coefficients which provide a means for comparing the various pavement structures

  Authors: Norwood, Gregory; Kwon, Jayhyun; Tingle, Jeb S.; Wayne, Mark H.
  Authors: Norwood, Gregory; Kwon, Jayhyun; Tingle, Jeb S.; Wayne, Mark H.
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Pavements
  Session: 623
  Paper Number: 13-4737