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In this study, the suitability of developing and applying different types of geogrids to increase road-subbase bearing capacity was investigated. Textile products obtained from natural jute fibers were transformed into a geogrid and used in the road subbase. Studies have revealed that natural fibers, typically obtained from agricultural waste, can be spontaneously degraded via natural processes. Therefore, the jute textile geogrid surface was coated with bituminous materials. In addition, commercially available geogrid materials made using basalt fibers were included as a road-subbase reinforcement in the study for a comparative analyze. The study was performed on a subbase material used in the subbase of a road. The developed and commercial geogrids were classified into different sample groups and subjected to ground tests. In the first group, tests were conducted on the road subbase material without using a geogrid. Thus, the basic physical properties and the California bearing ratio (CBR) values were determined and used as a reference for the bearing strength parameters of the ground. The second group was tested using the basalt geogrid on the same subbase material. The third group was subjected to the same tests using an uncoated geogrid developed with natural jute fibers. Finally, the fourth group was exposed to the same tests after the surface of the jute-fiber geogrid was coated with bitumen. Thus, four sample groups, including a reference (control), were evaluated for comparison. Test results indicated that the bearing strength of geogrid samples with natural fibers increased by 39.7% and 48.5% compared to control samples for CBR values of 2.5 and 5 mm, respectively. In addition, the bearing capacity of bitumen-coated natural jute-fiber geogrid samples increased by 17.8% and 22.4% for CBR values of 2.5 and 5 mm, respectively. After analyzing the bearing capacity of basalt geogrid samples, increases of 6.68% and 5.05% were obtained for CBR values of 5 and 2.5 mm, respectively, compared with reference samples. [ABSTRACT FROM AUTHOR]

This paper presents heave and pullout studies of plain granular pile-anchors (GPAs) and geogrid-encased GPAs. Experiments were conducted in California bearing ratio (CBR) moulds and fabricated moulds of size 381 × 381 × 457 mm in expansive clays. The GPA method is an innovative technique developed for reducing heave and improving bearing capacity and pullout capacity. In this study, GPAs were encased in geogrids to augment the engineering performance of the system. Tests were conducted in CBR moulds and fabricated larger moulds to study and compare the heave and pullout behaviour of plain GPAs and geogrid-encased GPAs. The results indicated that the clay beds reinforced with geogrid-encased GPAs showed better heave and pullout behaviour. Heave decreased by 90.8% and 92.5%, respectively, in the case of plain and geogrid-encased GPAs installed in the CBR moulds and by 95.12% and 98.3% in the case of plain and geogrid-encased GPAs installed in fabricated large moulds. Pullout load on geogrid-encased GPAs in CBR moulds improved by 42.17% over that on plain GPAs and pullout load on geogrid-encased GPAs in the fabricated large moulds improved by 52.25% over that on plain GPAs. [ABSTRACT FROM AUTHOR]

Pavements constructed over poor subgrade soil will lead to rapid increase in construction and maintenance costs due to increase in crust thickness and frequent failure. In a developing country, like India, costs play a very significant role. In India, more than 20% of the land area is covered with soils having low California bearing ratio (CBR) and shear strength values. These soils consist of a substantial amount of fines; i.e., a high percent of silt and clay, losing significantly in strength upon coming in contact with water. This paper presents the effect of geogrid reinforcement on the strength behaviour of poor subgrade soil. The geogrids are placed in single and double layers from the top of mold and heavy compaction and soaked CBR tests are performed. It is observed that geogrid reinforcement increases the CBR value significantly, thus causing significant reductions in pavement thickness and cost. Multiple linear regression models were developed for predicting soaked CBR. [ABSTRACT FROM AUTHOR]

This study attempts to identify mechanical and physical properties of geogrids that are critical to their effectiveness in the stabilisation of pavement subgrade. Geogrid properties, including aperture size, wide-width tensile strength and junction strength, for four geogrid products are correlated with bench-scale interface test results, including direct shear and pull-out, and accelerated pavement testing (APT) results. APT is conducted through the use of a one-third scale APT device, the model mobile load simulator (MMLS3) on geogrid-reinforced pavement sections. The pavement sections are constructed on a subgrade soil with a low California bearing ratio. The performance of each pavement section is evaluated by measuring surface rutting at various trafficking stages. The analysis reveals a strong relationship between performance and junction and tensile strength of geogrids at small strains, whereas aperture size has a positive correlation with pull-out test results. [ABSTRACT FROM AUTHOR]