Browsing by Subject "Geotextiles"
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Item Anti-capillary barrier performance of wicking geotextiles(2012-08) Azevedo, Marcelo Moraes de; Zornberg, Jorge G.; Romanovicz, Dwight K.A capillary barrier develops and restricts water flow when two porous materials with dissimilar pore structures (e.g., a coarse-grained soil overlain by a fine-grained soil) are in contact with one another. This is due to a difference in the unsaturated hydraulic conductivity of the two materials at a given suction. Geotextiles are utilized in a variety of civil engineering applications and have a pore structure similar to that of a coarse-grained soil. This can be problematic in unsaturated soil as the capillary barrier caused by the geotextile may instigate undesirable moisture buildup in the overlying soil and undermine any benefit provided by the geotextile. Various versions of a new geotextile have been manufactured to help dissipate a capillary barrier by "wicking" or laterally draining excess moisture away from the soil. Additionally, nonwoven blends of the unique wicking fiber combined with standard polymeric fibers are tested to assess their ability to minimize the development of a geotextile capillary barrier and not cause additional moisture accumulation in the first place. The unsaturated properties of both woven and nonwoven configurations of these wicking geotextiles were investigated as part of a comprehensive an experimental testing program. The testing program includes small soil column infiltration tests to assess geotextile capillary barrier performance with moisture monitored by time domain reflectometers and capacitance probes. Also, modified hanging column tests were conducted to define the hydraulic properties of the geotextiles in the form of water retention curves. Finally, a microscopy study, involving both optical and scanning electron microscopes, was conducted to observe the wicking behavior of the geotextiles at a micro-scale level. Test results illustrate the enhanced lateral drainage and reduced moisture accumulation of the wicking geotextiles when compared to regular geotextiles. Additionally, the woven version of the wicking geotextile has the potential to perform the functions of separation, filtration, protection, reinforcement, and drainage. All of these functions in a single geosynthetic product could lead to significant cost savings compared to the use of separate products to perform each one of the various functions.Item Modification of waste water treatment using geotextiles(Texas Tech University, 2001-05) Kotha, Kishore KumarRemoval of suspended solids (SS) is one of the unit operation involved in the treatment of wastewater. Sedimentation process is widely used for the removal of SS from wastewater. But this method also has some disadvantages such as sludge handling and low removal efficiencies. In this investigation, nonwoven geotextiles with varying hydraulic and mechanical properties were used to treat municipal wastewater. Also, the performances of different geotextiles in treating wastewater with varying influent SS concentrations, were evaluated. Geotextile retains SS on its upstream face as wastewater is passed through it. Once the geotextile is clogged, it was backwashed with tap water for reuse. Our investigations revealed that the geotextiles were able to achieve very high removal efficiencies in the range of 70-90%, irrespective of the influent SS concentrations. But with a higher range of influent SS concentration (>200mg/L). the geotextiles exhibited very short clogging time, around 5 to 10 min., which required backwashing geotextiles every 10 min. This technique may prove to be suitable for treating low strength and low flow wastewaters having SS concentrations in the range of 100to200mg/L.Item Use of geotextiles with enhanced lateral drainage in roads over expansive clays(2015-05) Garcia Delgado, Ivan Enrique; Zornberg, Jorge G.; Bhasin, AmitExpansive 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.