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Hydrologic Evaluation of Landfill Performance (HELP) model is one of the most accepted tools to simulate

the hydrological attributes of landfills. Although some major deviations from real values has been reported about the

calculated results for leachate generation by HELP model but other researchers and/or engineers in practice have

used it in some places to estimate amount of leachate produced in the landfills. On the Other hand this model is

elaborated and mainly used in developed countries with the waste having low moisture content and also in climatic

conditions with high precipitation. This research investigated the applicability of the model in arid areas, by

construction of two 30m× 50m (effective horizontal length) test cells in Kahrizak landfill (longitude=51°, 20',

latitude= 35° 27' degrees), and monitoring the real leachate generation from each one. A set of field capacity and

saturated water conductivity tests were also performed to determine basic hydrologic properties of municipal waste

landfilled. A comparison was made between values calculated by HELP model and recorded values, shows that a

prediction of leachate on annual basis can be done by HELP model with acceptable accuracy but when the infiltration

of water to waste body increases due to leachate production, the model intents to underestimate water storage capacity

of the landfill, which lead to deviation of calculated values from real ones.

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Municipal Solid Waste (MSW) materials are among the most complicated materials for geotechnical engineering as their composition includes an organic fraction, which suffers loss of mass over time, and a fibrous part, which acts as reinforcement, governing the MSW shear behavior. Because of these characteristics MSW can be described as a viscous material which shows time dependent behavior. Since the decomposition of MSW leads to gas and leachate generation, the changes in the MSW’s mechanical behavior could be linked to gas emission and leachate production from landfills. This paper deals with the characteristics of MSW materials to provide the necessary data for efficient and safe landfill design, construction and operation. The MSW physical characteristics such as composition, water content and organic content at varying ages, field and laboratory measurements of methane generation and leachate production, MSW compressibility behavior and its shear strength are covered. By presenting these data the authors hope to promote a better understanding of the mechanical behavior of MSW and provide useful data for use in landfill management tasks.

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The main purpose of this study is to investigate the influence of urban solid waste leachate on the mechanical properties of the soil. Order to provide a more accurate identification of the contaminated soils, Cylindrical specimens of the soil, according to the density curves with different initial conditions (different initial contamination levels) were prepared, then the soil specimens were loaded at different load levels using a direct shear testing equipment and a universal testing machine to apply axial compression on the specimens. By analyzing the results, the stress-strain and failure behavior of the soil specimens containing different percentages of the solid waste leachate was evaluated. The most important result was reducing the mechanical properties of the soil contaminated with different percentages of solid waste. The results of adding lower quantities of leachate, is far more significant compared to the received results from adding higher amounts of leachate.