Slope Stability Analysis of Industrial Solid Waste Landfills
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
With increasing industrialization, the waste generated has also increased. Sweden generate greatamount of industrial waste every year. In 2008, there were 97.9 million tons of waste generated, out ofwhich 93 million tons were industrial waste. Mining waste made up the majority of the total wasteamounting to more than 58 million tons of the waste generated in Sweden (Avfall Sverige, 2011).64.1% of industrial wastes were deposited in the landfill sites (Jia, 2011).According to Avfall Sverige (2011), 85 landfills were open as at 2009 in Sweden. A large number ofthese landfill sites take non-hazardous waste, while 21 of them accept hazardous waste. 5 of the sitesare limited to inert waste. Landfills that are in the closure stage must be covered with a final cover.Together these landfills cover an estimated area of 25km2, and the estimated total cost for finalcovering of the sites is about 6 billion SEK. Approximately 6-8 million tons of material is used for thefinal covers of landfill sites every year. Because natural material is not always available, secondaryconstruction materials is used instead.Secondary construction materials for the final cover of a landfill is an attractive alternative for manylandfill operators in order to reduce material cost and exploitation of non-renewable virginconstruction materials such as clay and sand. Secondary construction materials that have beeninvestigated and used in different final cover designs are ash, slag from steel making, sewage and fibersludge, treated soil and compost (Travar et. al., 2005, Kim et. al., 2005, Andreas et. al., 2005,Tham et. al., 2003, Kumar et. al., 2003). However, companies and authorities do not know theuncertainty in terms of mechanical stability of these secondary construction materials used in the covermaterial.Stability is a very significant part of the landfill design, especially in a multilayered final cover. Slopefailure of landfill can occur during the construction of landfill, during filling or after closure of thelandfill. Most landfill failures have occurred in slopes of waste, and also in interfaces betweengeosynthetic-geosynthetic and soil-geosynthetic materials. Landfill failures can have disastrous resultincluding loss of life, damage to property, and pollution of the surrounding environment, surface andgroundwater. Therefore the stability of landfill must be dealt with very carefully so as to know howsafe a landfill is or how hazardous a landfill is. This is the essence of our master’s thesis.Direct simple shear test was found to be suitable to determine the shear strength parameters of somefinal cover materials. Based on the laboratory investigation the cohesion of compost, bio-ash,excavated materials, a mixture of green liquor and sludge and rock dust were found to be in the rangeof 0-2.35kPa. The friction angles of these materials were found to be between 15-33 degrees.Different side slopes of landfill were analysed with the SLOPE/W and PLAXIS 2D program. Theseprograms are intended for soil but were found proper for slope stability of landfills. While using theIVSLOPE/W software, our analysis on side slopes with values1:3, 1:4, 1:5 gave a factor of safety of1.08 - 1.25, 1.53 - 1.62 and 1.79 - 1.96 respectively. The PLAXIS software also gave a factor of safetyof 0.9, 1.14 and 1.46 respectively for the same side slopes. Comparing the results we got with thefactor of safety 1.5 used in geotechnical analysis for slope stability, it can be inferred that side slope of1:3 for both SLOPE/W and PLAXIS is less than the recommended value of 1.5. This implies that thelandfill with side slope of 1:3 is not safe with both programs. On the other hand, with a side slope of1:4 SLOPE/W gives a factor of safety greater than 1.5 whereas PLAXIS gives a factor of safety lessthan 1.5.This implies that with a side slope of 1:4, SLOPE/W is safer than PLAXIS. Interestingly, witha side slope of 1:5, both SLOPE/W and PLAXIS gives a safe factor of safety.Since the Obbola landfill has a side slope of 1:4, SLOPE/W indicates a safe factor of safety butPLAXIS indicates that the side slope is unsafe. This is based on our computation and the engineeringjudgement we made in the analyses as above.
Place, publisher, year, edition, pages
2012. , 77 p.
Teknik, Slope Stability, Industrial Waste, Landfills, SLOPE/W, PLAXIS 2D, Factor of Safety
IdentifiersURN: urn:nbn:se:ltu:diva-52669Local ID: 9c56f3b6-1759-4142-8335-292e0419336eOAI: oai:DiVA.org:ltu-52669DiVA: diva2:1026040
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Validerat; 20120604 (anonymous)2016-10-042016-10-04Bibliographically approved