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. �`�� ^�Mx)�.'•Y;�°.5�.'#.•'y;7� _,..a!tlaSR^l': `k:• v.%7>.+.. ..,rti�.`.r 7'�n•. . .n-.+ c ? Pr station and Dis uttlnn of Resul[s In a contour plot, a contour line represents the same elevation along a line. A closed contour therefore indicates either, a depression or a mous The presence of closed contours representing a deep depression is an unacceptable condition i - the design of a liner system. The deformed surface elevations in each grid point are calculated by the computer program. The deformed surface contours on the 7 percent sloping surface are then plotted for each case, as shown on Figures EX—1 - EX 4. Where the thickness -of the soil/waste layer is 1.8 m (6 feet), as shown on Figure EX 1, the presence of the void will create a depression 9 em (0.3 feet) deep. This depression could trap and accumulate liquids, hindering -the free flow of leachate towards a collection point. When the thickness of the soil/waste layer above the void is increased to . 2.25 m (7.5 feet), the depression .is seduced to less than 3 cm (-0.1 foot), as shown on Figure EX 2. With a 2.7 in (9 foot) tluck soil/waste layer over the void, the depression disappears. The disturbance in the liner surface decreases as the depth to the void increases, as seen when the thickness of the soil/waste layer is increased to 3.6 m (12 feet) (Figure EX—3 and EX 4). To evaluate the potential for grade reversal, a characteristic curve of required soil/waste thicknesses M over a 0.9 m (3 feet) wide by 0.9 in (3 feet) deep by 1.8 m (6 feet) long void versus liner surface grades (a) is il-lustrated on Figure 3. 5 n E iZ 4 N R7 N � N C 3. E s o ►— U � 2. p m >` p N Ck: p �. V) v 0.1 0 5 10" 15 (V20 25 30 35 40 Conioinmenl liner Grade (degree) Figure 3 Required controlled fill thickness to prevent grade reversal ('T) versus containment liner grade (a) on 0.9m x 0.9m x 1.8m (3'x3'x6') void Geosynthuics '93 - Vancouver, Canada -1305 n