Evaluation of geogrid displacement on subbase reinforcement using specially designed pullout test


AKPINAR M. V. , Sert T.

8th International Conference on the Bearing Capacity of Roads, Railways and Airfields, Illinois, Amerika Birleşik Devletleri, 29 Haziran - 02 Temmuz 2009, ss.1117-1123 identifier identifier

  • Cilt numarası:
  • Basıldığı Şehir: Illinois
  • Basıldığı Ülke: Amerika Birleşik Devletleri
  • Sayfa Sayıları: ss.1117-1123

Özet

The main objective of this study was to determine vertical and horizontal displacements of geogrid samples during pullout tests. Laboratory pullout tests were performed on 1.5 m long 1 m wide geogrid specimens using the same type of soils at similar moisture content and density. Vertical and horizontal displacements of aggregates and geogrids during the pull tests were computed by utilizing digital image processing. Sensors mounted above and below the geogrid samples were used to monitor displacements during the tests. The digital image process was conducted through the 300 mm long and 150 mm plexiglas windows opened on the sides of the special designed large scale pullout test device. A feature of the testing program is that displacements of geogrid samples at each connection of longitudinal and transverse ribs were captured and computed through non-contact measurements. The vertical and horizontal displacements of the geogrid ribs (transverse and longitudinal) were found to be very small.

The use of a proper geogrid reinforcement material drastically reduces the subbase settlement problems due to high interface shear strength. The main interaction mechanisms affecting the shear resistance of extruded geogrids are the skin friction, between soil and reinforcement solid surface, and the bearing resistance, which develops against longitudinal and transverse members of geogrid on the interface shear behavior. The main objective of this study was to determine the geogrids vertical and horizontal displacements during the pullout tests. Laboratory pullout tests were performed on 1.5 mt long x 1 mt wide geogrid specimens using the same type of soil at similar moisture content and density. Vertical and horizontal displacements of aggregates and geogrids during the pull tests were computed using the strain gauges and utilizing the digital image processing. All sensors used to monitor displacement rate and pressure during a test were mounted above and below the geogrid samples. It was found that the normal pressure on the geogrids were not homogenous distributed rather it was random varying from 10 kPa to 45 kPa. Digital image process was conducted through the 300 mm long and 150 mm plexiglas windows opened on sides of the special designed large scale pullout test device. The vertical and horizontal elongations of the geogrid members (transverse and longitudinal) were found to be very small. During these tests it was determined that there is an effect of the geogrid opening size on the bearing capacity at even very small deformations.