An approach using strength reduction factor (SRF) for finite element analysis, with the provision of a failure criterion, and incorporation of graphical output, to examine the failure zone developed, was used in order to determine slope failure and the corresponding safety factor. The state of the effective stresses in a slope is calculated by the finite element method using eight-node quadrilateral elements of elastic-plastic soil with the Drucker-Prager nonlinear stress-strain relationship and a nonassociated flow rule. Slope failure occurs when the yield zone spreads over the entire slip surface and the corresponding SRF is the safety factor of the soil slope. The slope failure could be clearly defined and progressive failure was also observed. It should be kept in mind that the critical slip surface is not unique. A narrow yielding zone was developed when the slope started to fail and any slip surface passing through the yield zone could be the failure surface. The factor of safety obtained by the proposed procedure is in good agreement with that determined by Bishop's method
Municipal solid waste management (MSWM) is an important environmental challenge and subject in urban planning. A sustainable MSWM strategy should consider not only economic efficiency but also life-cycle assessment of environmental impact. This study employs the fuzzy multiobjective linear programming (FMOLP) technique to find the optimal compromise between economic optimization and pollutant emission reduction for the MSWM strategy. Taichung City in Taiwan is evaluated as a case study. The results indicate that the optimal compromise MSWM strategy can reduce significant amounts of pollutant emissions and still achieve positive net profits. Minimization of the sulfur oxide (SO x ) and nitrogen oxide (NO x ) emissions are the two major priorities in achieving this optimal compromise strategy when recyclables recovery rate is lower; however, minimization of the carbon monoxide (CO) and particulate matter (PM) emissions become priority factors when recovery rate is higher.Implications: This paper applied the multiobjective optimization model to find the optimal compromise municipal solid waste management (MSWM) strategy, which minimizes both life-cycle operating cost and air pollutant emissions, and also to analyze the correlation between recyclables recovery rates and optimal compromise strategies. It is different from past studies, which only consider economic optimization or environmental impacts of the MSWM system. The result shows that optimal compromise MSWM strategy can achieve a net profit and reduce air pollution emission. In addition, scenario investigation of recyclables recovery rates indicates that resource recycling is beneficial for both economic optimization and air pollutant emission minimization.
Municipal solid waste management (MSWM) is an important environmental challenge and subject in urban planning. For sustainable MSWM strategies, the critical management factors to be considered include not only economic efficiency of MSW treatment but also life-cycle assessment of the environmental impact. This paper employed linear programming technique to establish optimal MSWM strategies considering economic efficiency and the air pollutant emissions during the life cycle of a MSWM system, and investigated the correlations between the economical optimization and pollutant emissions. A case study based on real-world MSW operating parameters in Taichung City is also presented. The results showed that the costs, benefits, streams of MSW, and throughputs of incinerators and landfills will be affected if pollution emission reductions are implemented in the MSWM strategies. In addition, the quantity of particulate matter is the best pollutant indicator for the MSWM system performance of emission reduction. In particular, this model will assist the decision maker in drawing up a friendly MSWM strategy for Taichung City in Taiwan.Implications: Recently, life-cycle assessments of municipal solid waste management (MSWM) strategies have been given more considerations. However, what seems to be lacking is the consideration of economic factors and environmental impacts simultaneously. This work analyzed real-world data to establish optimal MSWM strategies considering economic efficiency and the air pollutant emissions during the life cycle of the MSWM system. The results indicated that the consideration of environmental impacts will affect the costs, benefits, streams of MSW, and throughputs of incinerators and landfills. This work is relevant to public discussion and may establish useful guidelines for the MSWM policies.
Municipal solid waste management (MSWM) is an important, practical and challenging environmental subject. The processes of a MSWM system include household collection, transportation, treatment, material recycling, compost and disposal. A regional program of MSWM is more complicated owing to the involvement of multi-municipality and multi-facility issues. Therefore, an effective decision support system capable of solving regional MSWM problems is necessary for decision-makers. This article employs linear programming techniques to establish a MSWM decision support system (MSWM-DSS) that is able to determine the least costs of regional MSWM strategies. The results of investigating a real-world case in central Taiwan indicate that a regional program is more economical and efficient. For the redeployment of MSW streams, the relatively least cost of operation for the MSWM system can still be achieved through the re-estimation of the MSWM-DSS. This tool and results are useful for MSWM policy-making in central Taiwan.
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