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School of Civil and Environmental Engineering Life Impact The University of Adelaide Water Balance and the Influence of Soil Structural Changes on Final.

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Presentation on theme: "School of Civil and Environmental Engineering Life Impact The University of Adelaide Water Balance and the Influence of Soil Structural Changes on Final."— Presentation transcript:

1 School of Civil and Environmental Engineering Life Impact The University of Adelaide Water Balance and the Influence of Soil Structural Changes on Final Covers for Landfill Closure Melissa Salt, University of Adelaide Mark Jaksa, University of Adelaide Jim Cox, CSIRO Paul Lightbody, Tonkin Consulting

2 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 1 Research Objectives Measure and compare the drainage to determine if phytocovers reduce drainage to the same extent as conventional covers Correlate changes in drainage patterns over time from the phytocover and conventional cover changes with changes in bulk density, soil water characteristic curve and permeability Assess the tendency for anthropomorphic soil to tend towards the natural profile of the borrow source or toward a new stable profile Determine the effect of changes in bulk density, soil water retention curve and permeability on the predictability of the water balance as estimated from pre-construction laboratory testing

3 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 2 Water Balance P = ET + R + L + D + ΔS WASTE COVER Precipitation (P) Runoff (R) Leachate Drainage (D) Lateral flow (L) Soil moisture storage (S) Evapotranspiration (ET)

4 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 3 Methodology – Field Scale Precipitation - Weather station Runoff - Flow meters Drainage and lateral flow - Tipping bucket rain gauges Soil moisture content – MP406 Soil suction – CS229 Drainage layer Root barrier Runoff collection Drainage collection Soil cover layer 1.5 mm LLDPE geomembrane Interim cover Earthen berms not to scale Monitoring nest

5 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 4

6 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 5

7 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 6

8 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 7

9 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 8

10 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 9 Methodology – Small Scale 1 m x 1 m x 1.5 m deep Replicate conventional and phytocover from Adelaide, including plants Irrigation and measure drainage Destructively sample 1 box of each cover type every 6 months Analyse samples for bulk density, soil water characteristic curve and permeability

11 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 10 Methodology – Core samples To measure any change in permeability or bulk density as a result of alternate saturation and then drying the soil layers proposed to use in the Adelaide A-ACAP trial. Prepared core samples at known bulk density of phytocover soil and clay barrier Wet using falling head permeability apparatus until saturated and hydraulic conductivity measured Dry in oven at 30 o C until equilibrated and observe shrinkage and cracking Repeat process

12 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 11 Water Balance Modelling Moisture content at depth through conventional profile over first 3 years modelled

13 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 12 Water Balance – Adelaide Site Water balance Phytocover (mm/yr & %)Conventional (mm/yr & %) 1 m1.5 m2 mAs placedDried P515 I117 (23)123 (24) 103 (20)125 (24) ET349 (68)357 (69)364 (71)412 (80)369 (72) R0.7 (0.1) 0.8 (0.1) L0000.50 D48 (9)34 (7)28 (5)0.2 (0)23 (4)

14 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 13 Water Balance Predictions Predicted annual runoff volumes when surface soil permeability is reduced by one order of magnitude

15 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 14 Results – Adelaide Soil Moisture

16 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 15 Results – Adelaide Topsoil Moisture Content

17 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 16 Results – Melbourne Soil Moisture

18 School of Civil and Environmental Engineering Life Impact The University of Adelaide Slide 17 Outcomes Water balance comparison of phytocaps for Australian environment Variability of water balance predictions from selected models Quantification of soil structural changes in the short to medium term Impact of soil structural changes on sustainability of the phytocaps Determination of best soil input parameters for pre-construction modelling


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