Geogrids in cold climate : Temperature controlled tensile tests & Half-scale installation tests at different temperatures

• Main Authors: Bonthron, Björn, Jonsson, Christian
• Format: Bachelor Thesis
• Language: English
• Published: Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser 2017
• Subjects: geogrid; cold climate; low temperature; tensile test; half-scale test; Geotechnical Engineering; Geoteknik; Luleå; Northern Sweden
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-63204

Due to the findings of extensive damage on geogrids used in a road embankment in northern Sweden, the Swedish Transport Administration (TRV) started to investigate the reason of these damages. Since the geogrids were installed at low temperature, below 0°C, it was suspected that the damages were connected the low temperature. To analyse whether low temperatures have an influence on the extent of installation damages, both a half-scale setup and temperature controlled tensile tests have been carried out on geogrids. In total five different types of geogrids have been tested; 3 extruded polypropylene geogrids, 1 woven PET geogrid, and 1 welded PET geogrid. All geogrids had an aperture size of approximately 35 mm and specified tensile strength of approximately 40 kN/m. The Half-scale tests was conducted by building a small road embankment inside a freeze container, at the Luleå University of Technology (LTU). The embankment contained crushed aggregate, type 0-70 mm, and geogrids. The purpose of the half-scale test was to simulate installation of geogrids at different temperatures and thereby investigate whether low temperatures have an influence on the rate of installation damages. The half-scale test was done for each type of geogrid at the temperatures: +20°C, -20°C and -30°C. First, the geogrid was covered by 150 mm of crushed aggregate. Then a vibratory plate (160 kg) was used to compact the crushed aggregate. After each installation, the crushed aggregate was removed carefully by vacuum suction. The geogrid was removed and then analysed by visual control and tensile tests conducted according to ISO 10319:2008 (wide width tensile test). Results from the half-scale tests indicate that 2 out of 5 of the tested geogrids were affected by the testing procedure. The results indicate that: - one of the geogrids of polyprophylene (here referred to as G2) was more damaged at lower temperatures compared to installation at +20° C. - the geogrid of woven PET (here referred to as G5) was less damaged at lower temperatures ...