Effect of Water Retention Properties of Municipal Solid Waste on Landfill Stability

Eric Nero Author

07/27/2020 Added

33 Plays

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In this study, the effect of water retention characteristics of fresh MSW and cover soils obtained from in situ samplings in several county landfills located in rural NE on the stability will be evaluated. With that, unsaturated hydraulic characteristics of the MSW and soils associated with precipitation and leachate circulation will be explored to investigate the landfill stability.

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[00:00:00.000]Hello, my name is Eric Nero and the title
[00:00:03.718]of my project is the Effect of
[00:00:05.388]water retention properties of municipal
[00:00:07.618]solid waste on landfill stability.
[00:00:11.054]The project overview includes 13 different
[00:00:13.324]simulation configurations that were
[00:00:14.753]evaluated to determine how MSW properties
[00:00:16.922]affect pore pressure stabilization time
[00:00:18.927]over a 300 day interval.
[00:00:20.514]Each simulation was run using 4 initial
[00:00:22.914]injection pressures of 49, 98, 147 and 196
[00:00:26.929]kilopascals.
[00:00:27.835]Anisotropy ratios of 1, 2, and 5
[00:00:30.430]were also simulated.
[00:00:32.425]A ratio of 1 was used in every simulation,
[00:00:34.629]while a ratio of 5 was used in simulations
[00:00:36.588]1 through 6, and 13,
[00:00:38.173]and the ratio of 2 was used in
[00:00:39.515]simulations 7 through 12 to see
[00:00:41.624]how the increased ratio will affect
[00:00:44.387]the pore pressure stabilization results.
[00:00:46.534]Slope stability analysis was evaluated
[00:00:48.600]at each initial injection pressure
[00:00:50.388]and each MSW simulation configuration.
[00:00:52.367]While also we determined change
[00:00:54.407]and stabilization in factor of safety
[00:00:57.611]values for each scenario.
[00:01:00.483]The breakdown of each simulation
[00:01:01.928]configuration is here in this table
[00:01:04.636]where we have the 13 different simulations.
[00:01:06.737]The first 6 include aged MSW as we see
[00:01:10.102]the fresh, 1 month old, 1 year old,
[00:01:12.648]3 years old, 6 years old, and 10 years old
[00:01:14.960]MSW, and these come from the first
[00:01:17.310]two studies, while simulations 7 through 13
[00:01:20.572]include different compaction levels
[00:01:22.596]such as fresh, low degraded,
[00:01:24.462]medium degraded, and high degraded MSW.
[00:01:27.241]And these come from the other two
[00:01:29.152]simulations while simulation 13 is our
[00:01:31.974]current study data.
[00:01:34.766]And now here we have the landfill geometry
[00:01:37.149]in GeoStudio where we have the red
[00:01:41.201]boundary along the face of the landfill
[00:01:43.958]is the zero pressure condition which
[00:01:45.680]simulates that no rainfall will hit the
[00:01:50.151]landfill, and we have the drainage
[00:01:52.043]condition which is the blue line at the
[00:01:53.524]bottom, which is simulating the leachate,
[00:01:56.967]or leftover water, flowing into the soil
[00:01:59.713]below the landfill.
[00:02:01.523]Then we have the red point which is the
[00:02:03.444]injection point where we will inject the
[00:02:06.210]initial leachate at the initial pressures
[00:02:10.727]as mentioned before, and directly to the
[00:02:13.233]left of it at 15 feet is the pore pressure
[00:02:16.820]measuring point, which is where we are
[00:02:18.434]taking the pore pressure values from
[00:02:22.025]in the SEEP/W results.
[00:02:24.189]Then the different colored layers
[00:02:25.933]are where we defined the different
[00:02:27.588]material layers in the different configurations
[00:02:30.355]based on parameters in past literature
[00:02:33.220]and volumetric water content and
[00:02:35.467]hydraulic conductivity functions as well.
[00:02:39.484]Now we can see from the SEEP/W and SLOPE/W
[00:02:42.373]results. For the SEEP/W results we start
[00:02:44.935]with the stabilization pore pressures
[00:02:47.543]As you can see when we have the initial
[00:02:49.310]pressure of 49 kPa, when we increase
[00:02:51.772]the anisotropy ratio from 1 to 2 to 5
[00:02:54.541]the overall pore pressure stabilization points
[00:02:57.607]do increase, but as we increase the
[00:02:59.981]initial injection pressures, the
[00:03:01.847]stabilization pore pressures actually
[00:03:03.954]decrease with the increase in the
[00:03:05.931]anisotropy ratios.
[00:03:08.184]Which correspond directly to the number
[00:03:09.703]of days it takes to stabilize for each
[00:03:11.556]simulation. As we can see in the gray
[00:03:13.958]we have the anisotropy ratio of 1 takes
[00:03:16.590]far longer than all of the other simulations
[00:03:19.379]and as we increase the anisotropy ratios
[00:03:23.292]from 2 to 5, which goes right along with
[00:03:26.551]that because as the stabilization pore
[00:03:28.489]pressures actually decrease and the anistropy
[00:03:31.309]ratios increase, which is the rate at which
[00:03:34.774]the water moves vertically.
[00:03:36.912]You would expect with more speed it would
[00:03:38.728]take less time to stabilize as the graphs show.
[00:03:43.045]Based on that, we looked at the stability
[00:03:45.811]analysis in SLOPE/W where we have the 4
[00:03:48.775]different studies and as you can see
[00:03:51.220]all 4 of them roughly start at about the same
[00:03:53.332]factor of safety at about a 2.15 to 2.17 range
[00:03:57.551]and they all stabilize at roughly the same
[00:04:00.239]factor of safety as well from about
[00:04:01.748]2.09 to 2.1 range, but the main
[00:04:04.539]difference is the number of days they
[00:04:05.956]took to stabilize. As you can see with
[00:04:08.021]the first three simulations it took only
[00:04:10.573]about 74 days to stabilize, while the next
[00:04:13.372]nine took 107 days and the current study
[00:04:17.000]data took 262 days to stabilize.
[00:04:21.929]Which these also follow directly from the
[00:04:23.720]SEEP/W results because as we can see
[00:04:26.669]with the first 3 simulations as compared
[00:04:29.233]to the next 9 and then the 13th simulation.
[00:04:32.492]The first 3 on average take less time
[00:04:35.028]than the next 9 simulations to reach their
[00:04:39.006]pore pressure stabilization points
[00:04:41.418]which means they would stabilize in factor
[00:04:44.073]of safety a little bit faster which they have
[00:04:48.681]and then the current study data took
[00:04:51.220]the longest to stabilize in pore pressure
[00:04:53.303]and it also took the longest to stabilize
[00:04:54.984]in the factor of safety.
[00:04:57.501]Overall as we expected based on previous
[00:04:59.865]literature each SEEP/W simulation resulted
[00:05:02.015]in the pore pressure stabilizing after so
[00:05:03.644]many days, while the different MSW
[00:05:05.664]layer combinations affected the number of
[00:05:07.589]days in which it took to stabilize.
[00:05:10.131]An increased anisotropy ratio also
[00:05:12.116]resulted in overall smaller pore pressure
[00:05:13.686]stabilization points, while also reducing
[00:05:15.733]the amount of time to stabilize.
[00:05:17.742]Then the slope stability analysis
[00:05:19.112]shows that each simulation configuration
[00:05:20.861]resulted in similar factor of safety
[00:05:22.608]results, meaning that the different
[00:05:24.322]combinations do not significantly affect
[00:05:26.095]the stability of the landfill.
[00:05:28.131]And compacted MSW, which were
[00:05:29.808]simulations 7 through 13 took longer to
[00:05:32.016]stabilize overall in factor of safety
[00:05:34.032]when compared to the aged MSW
[00:05:36.448]which were simulations 1 through 6.
[00:05:39.310]These are our references of the past
[00:05:41.088]literature and then the acknowledgements
[00:05:43.376]of Dr. Jongwan Eun and Sina Mousavi from
[00:05:46.727]the University of Nebraska-Lincoln
[00:05:48.176]for all of the help they've provided me
[00:05:49.606]and then the Unversity of Nebraska-Lincoln
[00:05:51.155]REU summer program for giving me the
[00:05:53.440]opportunity to fulfill this research.
[00:05:55.617]Thank you.

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Effect of Water Retention Properties of Municipal Solid Waste on Landfill Stability

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