In this paper, the performance of geogrid base reinforcement in flexible pavements was evaluated using cyclic plate load testing. A 40-kN cyclic load was applied through a 305-mm diameter steel plate. The investigated parameters included geometry, location and tensile modulus of geogrids. The stress distribution, permanent vertical strain and developed porewater pressure in the subgrade, as well as, the strain distribution along geogrids were studied. The test results showed that the inclusion of geogrid can significantly improve the performance of a flexible pavement and that the traffic benefit ratio can be increased up to 15.3 at a rut depth of 19.1 mm. Better performance was observed when geogrid layer was placed at the upper one-third of the base aggregate layer. The results also demonstrated that the geogrid helps in redistributing the applied load to a wider area on top of the subgrade layer, thus resulting in less accumulated permanent deformation in the subgrade.

This study evaluates the performance of geosynthetic-reinforced unpaved road sections over soft subgrade using plate load test. The parameters investigated included the location and tensile modulus of geosynthetics, and the number of geosynthetic layers. Stress distribution on top of the subgrade layer and strain distribution along the geosynthetic reinforcements were also investigated. The test results indicated that geosynthetic reinforcement resulted in appreciable reduction of surface deformation and increase of bearing capacity. The test results also demonstrated the effects of geogrid arrangement/location on the performance of unpaved test sections, with double reinforcement location consistently yielded the best improvement. The definite trend of increasing Bearing Capacity Ratio (BCR) and reloading elastic modulus with increasing tensile modulus of geosynthetics was observed when geosynthetics were grouped according to aperture shape and polymer type. The BCR is defined as the ratio of the bearing capacity of reinforced unpaved sections to that of unreinforced unpaved section.

This research evaluated the benefits of geogrid reinforcement of granular base specimens and studied the effect of different factors contributing to their performance. This includes geometry, tensile modulus, arrangement/location of geogrids, the moisture content of specimen, and stress state. Five geogrids of different tensile modulus and aperture geometries (three rectangle or biaxial and two triangle or triaxial) were used. The study was experimentally carried out by conducting repeated load triaxial (RLT) tests to evaluate the resilient and permanent deformations of the specimens. The test results demonstrated the potential benefit in placing the geogrid within the granular base specimens. Less permanent deformations were measured under cyclic loading for geogrid-reinforced base specimens compared to unreinforced specimens. The geogrid geometry and tensile modulus had noticeable effects on the specimens’ performance. Of the five geogrids used, the triaxial geogrid (TX1) with triangle geometry and the ...

A finite-element response model was developed using ABAQUS software package to investigate the effect of geogrid base reinforcement on the response of a flexible pavement structure. Finite-element analyses were then conducted on different unreinforced and geogrid-reinforced flexible pavement sections. In this analysis, the base course (BC) layer was modelled using an elasto-plastic bounding surface model. The results of the finite-element analyses showed that the geogrid reinforcement reduced the lateral strains within the BC and subgrade layers, the vertical strain and shear strain at top of subgrade, and the surface permanent deformation. The higher tensile modulus geogrid resulted in larger reduction of surface permanent deformation. Based on the response parameters computed from the finite element analysis, the improvement of using geogrid for BC reinforcement was then evaluated using the damage models for rutting in the mechanistic–empirical method developed through NCHRP Project 1-37a. The results of mechanistic–empirical analyses showed that the traffic benefit ratio values can reach as high as 3.7 for thin base pavement section built over weak subgrade using high tensile modulus geogrid.

An accelerated wheel load testing program was conducted to evaluate the benefits of using geosynthetics to enhance the performance of pavement constructed over soft subgrade. Six full-scale test sections were constructed, among which two sections were reinforced by one or two layers of triaxial geogrids, and two sections were reinforced by one layer of high strength geotextile with different base layer thickness. The test sections were instrumented by a variety of sensors to measure the load- and environment-associated pavement response and performance. The results of full-scale accelerated load testing demonstrate the benefits of using geosynthetics in terms of reducing the permanent deformation in the pavement structure. The geosynthetics benefit to reducing the maximum stress on top of subgrade is more distinguishable at a higher load level. It was also found that the geosynthetic placed at the base-subgrade interface was able to improve the performance of both subgrade and base layers. By placing an additional layer of geogrid at the upper one-third of the base layer, the performance of the base layer was further enhanced. While the geosynthetic showed appreciable benefit to reducing the permanent deformation of subgrade in this study, it showed little effect on the resilient properties of subgrade.

Soil cement as pavement base has been used in practice since 1915 due to its effectiveness in preventing pumping of the subgrade soils and its relatively high strength. In this research, the factors affecting the strength of cement-sand were investigated based on laboratory compaction tests and unconfined compression tests. The test results showed that the dry density, moisture content (w), water to cement ratio (w/c), initial void ratio (e _ini ), and cement content (C _w ) are the main controlling factors in the behavior of cementsand. A simple empirical correlation method is proposed to estimate the unconfined compressive strength of the cement-sand based on cement content, initial moisture content, and water to cement ratio. The tube suction tests were also performed in an effort to evaluate the water susceptibility of cement-sand, as the strength of cement soil can be affected by the soaking condition at field. The tube suction tests showed that the cement-sand can be classified as good quality base material based on the dielectric value.