Persistent Link:
http://hdl.handle.net/10150/290003
Title:
The effect of gas on general stability in wet landfills
Author:
Fritz, Wolfgang U.
Issue Date:
2003
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Due to regulatory legislation enacted over the past few decades, the design of municipal sanitary landfills has evolved from simple open dumps to relatively sophisticated storage and treatment facilities. Bioreactor landfills, which were first introduced in the mid 1990s became a popular landfill management technique and. A bioreactor landfill uses leachate recirculation to enhance the degradation processes thus degrading the waste constituents much faster than would be experienced with arid landfills. However, the well-accepted set of design criteria and methods of analysis for stability, settlement, degradation, gas generation, and water infiltration that had been developed for the arid landfills were not necessarily appropriate for the bioreactor landfills. Whether due to leachate recirculation or extreme precipitation, the waste in a landfill may tend to become saturated. The high saturation levels then reduce the permeability of the waste to landfill gas thus leading to pore pressures that are greater than what would be predicted by fluid statics. In this case, the factor of safety for global stability within the landfill will be lowered, potentially creating failure. A theoretical model predicting the time and depth dependent development pore pressures due to the formation of landfill gas in a wet landfill is presented. The model is then quantitatively approximated with a finite difference scheme. It was found that below the level of saturation, the steady state pressure distribution appears to be hydrostatic except that the unit weight of the fluid is significantly heavier (14.0 kN/m³) compared to water (9.81 kN/m³). In the ten days preceding July 10, 2000, approximately 0.75 m (30 inches) of rain fell onto the Payatas Landfill near Manila, Philippines. Results of HELP modeling indicate that this precipitation caused a 10-m deep zone of saturated waste at the bottom of the waste mass. Through a back-analysis of the failure, a factor of safety of 1.0 for stability was calculated by using an increased unit weight of pore fluid of 20.9 kN/m³, which is similar to that predicted by the finite difference scheme of 14.0 kN/m³. Hence, this research shows that the build-up of landfill gas can play a significant role in the stability of wet landfills.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Civil.; Engineering, Sanitary and Municipal.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Civil Engineering and Engineering Mechanics
Degree Grantor:
University of Arizona
Advisor:
Merry, Scott M.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleThe effect of gas on general stability in wet landfillsen_US
dc.creatorFritz, Wolfgang U.en_US
dc.contributor.authorFritz, Wolfgang U.en_US
dc.date.issued2003en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractDue to regulatory legislation enacted over the past few decades, the design of municipal sanitary landfills has evolved from simple open dumps to relatively sophisticated storage and treatment facilities. Bioreactor landfills, which were first introduced in the mid 1990s became a popular landfill management technique and. A bioreactor landfill uses leachate recirculation to enhance the degradation processes thus degrading the waste constituents much faster than would be experienced with arid landfills. However, the well-accepted set of design criteria and methods of analysis for stability, settlement, degradation, gas generation, and water infiltration that had been developed for the arid landfills were not necessarily appropriate for the bioreactor landfills. Whether due to leachate recirculation or extreme precipitation, the waste in a landfill may tend to become saturated. The high saturation levels then reduce the permeability of the waste to landfill gas thus leading to pore pressures that are greater than what would be predicted by fluid statics. In this case, the factor of safety for global stability within the landfill will be lowered, potentially creating failure. A theoretical model predicting the time and depth dependent development pore pressures due to the formation of landfill gas in a wet landfill is presented. The model is then quantitatively approximated with a finite difference scheme. It was found that below the level of saturation, the steady state pressure distribution appears to be hydrostatic except that the unit weight of the fluid is significantly heavier (14.0 kN/m³) compared to water (9.81 kN/m³). In the ten days preceding July 10, 2000, approximately 0.75 m (30 inches) of rain fell onto the Payatas Landfill near Manila, Philippines. Results of HELP modeling indicate that this precipitation caused a 10-m deep zone of saturated waste at the bottom of the waste mass. Through a back-analysis of the failure, a factor of safety of 1.0 for stability was calculated by using an increased unit weight of pore fluid of 20.9 kN/m³, which is similar to that predicted by the finite difference scheme of 14.0 kN/m³. Hence, this research shows that the build-up of landfill gas can play a significant role in the stability of wet landfills.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Civil.en_US
dc.subjectEngineering, Sanitary and Municipal.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineCivil Engineering and Engineering Mechanicsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMerry, Scott M.en_US
dc.identifier.proquest3119944en_US
dc.identifier.bibrecord.b45629559en_US
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