Use of geotextiles with enhanced lateral drainage in roads over expansive clays
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Expansive clays are very abundant across the central United States in general and in the state of Texas in particular damages induced by expansive clays have been reported to reach several billions of dollars per year. Volume changes in expansive soils due to change in their moisture content varies has caused significant cracking in roads and has resulted in costly maintenance projects over the lifetime of these roads. In Texas, expansive soils have been often treated with lime stabilization, which is not always possible, and in some cases by removing and replacing them with nonexpansive soils, which can be very costly. Recently, geosynthetic reinforcements have been incorporated in roads founded on expansive clays to make the structure stiffer and less prone to cracking. A new geotextile, which is capable of providing enhanced lateral drainage through capillarity has been recently develop. Facilitating moisture redistribution would be a feasible approach for roads on expansive clays as they may lead uniform vertical displacements resulting in minimized cracking in the asphalt layer. Eight test sections with different geotextiles were constructed on State Highway 21 in Bastrop, Texas. The road is founded on expansive clays. A number of geotextiles, including one with enhanced lateral drainage capabilities, were incorporated to 500 feet long test sections. All sections were equipped with sensors to monitor moisture beneath the geotextiles and were periodically surveyed to document pavement distresses. Results showed that the geotextile with enhanced lateral drainage was able to maintain a uniform moisture content along the length of the soil in contact with this geosynthetic. Condition surveys showed that the geotextile with enhanced lateral drainage prevented cracking in the portion of the pavement above it. As expected, cracks often developed in areas of the pavement section beyond the extent of the geotextile. This suggested that the geotextile was capable of providing enhanced lateral drainage, although placement of the geotextile over the full width of the road (and not only under the shoulder) would be necessary to minimize the development of longitudinal cracks. In conclusion, the geotextile with enhanced lateral drainage can deal with pavements on expansive clays by improving the pavements long-term performance.