Enhanced moisture management of pavement systems through capillary suction FIGURE 3 Silt column test configuration woven geotextile without the deepgroove fibers, (2) a woven monofilament geotextile, (3) a drainage composite made from high compressive strength cores and combined with nonwoven filter fabrics and (4) the ELDG. Each configuration was then underlain with an impermeable membrane to encourage lateral drainage, thus preventing any moisture from escaping directly underneath the geosynthetic, as seen in Figure 3. Results from these tests indicated that the ELDG removed 3%-4% more moisture from the soil column than any of the other geosynthetics, as shown in Figure 4. According to Budhu (2010), Equation 1 can be used to compare the undrained shear strengths of two samples of the same soil based on the differences in moisture content. (su)A (su)B = exp Gs(wB-wA) λ (1) where: su = undrained shear strength Gs = specific gravity of soil (~2.7 for silt) w = water content λ = compression index (0.15 typical for silt) FIGURE 4 Average moisture content distribution for silt column test 30 In this test, a 3% reduction in moisture content leads to q ~70% increase in undrained shear strength of the silt material. "Since all tested geosynthetics are permeable under saturated conditions and the heights of the soil columns were small (8 inches [200 mm]), gravity induced water flow will not cause differences in moisture content distributions in the soil columns. Therefore, the differences in moisture content distributions in the soil columns are caused by unsaturated water flow induced by differences in suction head" (Zhang and Belmont 2009). Geosynthetics | June July 2020 0620GS_p28-37.indd 30 5/20/20 6:15 PM