UNIVERSITA’ DEGLI STUDI DI PADOVA ICEA Department MSc in Environmental Engineering Master Thesis Massimo Trivellato Geotechnical Slope Stability of the Este MSW Landfill Supervisor Prof. Marco Favaretti Academic Year 2013-2014 Un ringraziamento sincero ai miei genitori, Gianpietro e Loredana INDEX Introduction .......................................................................................................................... - 9 - 1. Italian regulation about landfill slope stability ........................................................... - 10 - 2. Site description ............................................................................................................... - 11 - 2.1 Geographical Information .............................................................................................. - 11 - 2.2 Stratigraphy and Structure ............................................................................................. - 13 - 2.3 Hydrological properties ................................................................................................. - 14 - 2.4 Climate of the site .......................................................................................................... - 16 - 2.5 Seismology ..................................................................................................................... - 17 - 2.6 S.E.S.A. waste treatment activities ................................................................................ - 18 - 2.7 S.E.S.A. landfill description .......................................................................................... - 20 - 2.7.1 General information ............................................................................................. - 20 - 2.7.2 Principal administrative deeds ............................................................................. - 21 - 2.7.3 Sectors and subsectors ......................................................................................... - 22 - 2.7.4 Bottom liner systems ........................................................................................... - 26 - 2.7.5 Top cover systems ............................................................................................... - 26 - 2.7.6 Biogas management ............................................................................................. - 28 - 2.7.7 Leachate management ......................................................................................... - 30 - 2.7.8 Monitoring and control plan ................................................................................ - 31 - 3. General slope stability concepts .................................................................................... - 33 - 3.1 Introduction .................................................................................................................... - 33 - 3.2 Factors of influence........................................................................................................ - 34 - 3.3 Types of landfill’s failure............................................................................................... - 36 - 3.4 Seismic contribution ...................................................................................................... - 40 - 4. Slope Stability Analysis methods .................................................................................. - 43 - 4.1 Introduction .................................................................................................................... - 43 - 4.2 General concepts of Limit Equilibrium Methods .......................................................... - 44 - 4.3 LEM – Method of slices ................................................................................................ - 47 - 4.3.1 General formulation ............................................................................................. - 50 - 4.3.2 Fellenius method/OMS ........................................................................................ - 51 - - 5 - 4.3.3 Bishop’s rigorous method .................................................................................... - 52 - 4.3.4 Bishop’s simplified method ................................................................................. - 53 - 4.3.5 Janbu’s simplified method ................................................................................... - 53 - 4.3.6 Janbu’s generalized method................................................................................. - 55 - 4.3.7 Morgenstern – Price method................................................................................ - 55 - 4.3.8 Spencer’s method ................................................................................................ - 55 - 4.3.9 Lowe – Karafiath’s method ................................................................................. - 56 - 4.3.10 Corps of Engineers method ............................................................................... - 56 - 4.3.11 Sarma’s method ................................................................................................. - 56 - 4.3.12 General limit equilibrium formulation .............................................................. - 57 - 4.3.13 Considerations on the interslice force function ................................................. - 59 - 4.3.14 Summary of the method of slices approaches ................................................... - 60 - 4.4 General concepts of Finite Element Method ................................................................. - 62 - 5. Definition of the input sections and parameters ......................................................... - 64 - 5.1 Chosen landfill sections for the calculation ................................................................... - 64 - 5.2 Geotechnical input data.................................................................................................. - 67 - 5.2.1 Material properties ............................................................................................... - 67 - 5.2.2 Waste properties considerations .......................................................................... - 68 - 5.2.3 Waste properties for Este’s landfill ..................................................................... - 72 - 5.2.4 Pore water pressure .............................................................................................. - 73 - 5.2.5 Reinforcement of soil – structure interaction ...................................................... - 73 - 5.2.6 Imposed loading .................................................................................................. - 75 - 6. Calculation procedure using LEM software: SLOPE/W ........................................... - 76 - 6.1 Introduction .................................................................................................................... - 76 - 6.2 Slip surface shapes ......................................................................................................... - 77 - 6.2.1 Grid and radius method ....................................................................................... - 77 - 6.2.2 Entry and exit method.......................................................................................... - 79 - 6.3 Analysis of section 4-4................................................................................................... - 80 - 6.3.1 Stability Analysis of the top cover system along the steepest slopes .................. - 81 - 6.3.2 Stability Analysis of the entire landfill section ................................................... - 83 - 6.3.3 Stability Analysis of the entire landfill section varying waste parameters .......... - 85 - 6.4 Analysis of section 2-2................................................................................................... - 86 - - 6 - 6.4.1 Stability Analysis of the top cover system along the steepest slopes .................. - 87 - 6.4.2 Stability Analysis of the entire landfill section ................................................... - 89 - 6.4.3 Stability Analysis of the entire landfill section varying waste parameters .......... - 92 - 6.5 Analysis of section A-A ................................................................................................. - 92 - 6.5.1 Stability Analysis of the top cover system along the steepest slopes .................. - 93 - 6.5.2 Stability Analysis of the entire landfill section ................................................... - 94 - 6.5.3 Stability Analysis of the entire landfill section varying waste parameters .......... - 97 - 7. Calculation procedure using FEM software: PLAXIS............................................... - 98 - 7.1 Introduction .................................................................................................................... - 98 - 7.2 Phi-c reduction safety analysis....................................................................................... - 99 - 7.3 Analysis of section 4-4................................................................................................. - 100 - 7.4 Analysis of section 2-2................................................................................................. - 101 - 7.5 Analysis of section A-A ............................................................................................... - 102 - 8. Discussion of the results..............................................................................................