Environmental loads on control and geosynthetic stabilized pavements over expansive clay subgrades

Expansive clay subgrades have been reported as one of the major sources for damages to roadways in central and east Texas. The frequent and predominant form of damage to roadways over expansive clay subgrades includes longitudinal cracks, which are usually induced by heave and settlement of the expansive clay subgrades due to environmental changes. Over the past years, the Texas Department of Transportation (TxDOT) has utilized geosynthetic stabilization of the base course to mitigate detrimental impacts from expansive (high-plasticity) clay subgrades. The efficiency of this technique has often been evaluated by studying the extents of environmental longitudinal cracks on roadways that were constructed with or without geosynthetic stabilization. This research elaborates three types of roadway design that were founded on expansive clay subgrades. Turnersville Road and Farm to Market Rod 972 (FM 972) were not stabilized with any geosynthetic products. FM 1979 and FM 2924 were stabilized with single geosynthetic in the base course along all the sections. Cabeza Road and FM 1915 were both stabilized with geosynthetics, but more than one type. Two sections of Cabeza Road were constructed using two triangular geogrids with different characteristics while the third section was constructed without geogrid. FM 1915 was also designed with a non-stabilized control section and two geogrid stabilized sections, but the thicknesses of base layers were slightly different. A comprehensive monitoring program was conducted to evaluate the mechanism resulting the development of environmental longitudinal cracks and to compare the performance of different roadway designs under environmental loads. Specifically, status and severity of the environmental longitudinal cracks, identified as the main damage caused by the expansive clay subgrade, were documented in each test section through rigorous visual condition surveys. Vertical movements of the pavement over time trigged by periodically swell and shrinkage of the expansive clay subgrade was measured with total station. Environmental conditions of the field site, in forms of temperature and precipitation changing, were closely tracked too. Additionally, several in-situ tests as Automatic Plate Load Test (APLT), Dynamic Cone Penetration (DCP), and Falling Weight Deflectometer (FWD) were conducted as extra benefits in evaluating the pavement behavior. Analysis of the data collected from field sites provided evidence for mechanisms that result in the initiation and development of environmental longitudinal cracks. Also, comparison of the performance of various test sections underscored the advantages of geosynthetic stabilization in mitigating the damage caused by expansive clay subgrade. Moreover, the observed difference from test sections stabilized with different geosynthetic products proved the influence of geosynthetic properties in base stabilization.Civil, Architectural, and Environmental Engineerin