Factors affecting the shear strength behavior of municipal solid wastes.

In this study, the shear strength behavior of European (E-1), Turkey (T-1), and United States of America (U-1) average synthetic municipal solid waste (MSW) compositions were investigated. The large-scale direct shear tests were conducted using fresh and aged MSW samples collected from the Manisa Landfill. The natural samples' test results were compared with synthetic samples. The affecting factors such as ageing, waste composition, and waste type (synthetic and natural) on the shear strength of MSWs were investigated. The effect of composition was evaluated using three main and six modified synthetic MSW compositions. In addition to the synthetic fresh MSW samples, synthetic aged samples were also used. Angle of shearing resistance decreased with increasing organic content whereas cohesion intercept increased with increasing organic content. The fresh and aged wastes with higher coarse fraction lead to a higher angle of shearing resistance. The synthetic aged samples had higher internal friction angles but lower cohesion values than the synthetic fresh samples. Waste with average European composition had the highest internal friction angle as it has the highest fibrous content. On the other hand, the highest cohesion belonged to the Turkey composition, which had the highest organic matter ratio. The main differences between E-1, T-1 and U-1 samples in terms of compositions were observed. The results of this study indicated that shear strength of waste significantly depends on composition and hence a site specific evaluation is recommended.

Suction characteristics of compacted zeolite-bentonite and sand-bentonite mixtures.

Soil suction is one of the most important parameters describing soil moisture conditions for unsaturated soils used in landfill liners. However, few studies have been conducted on the suction characteristics of compacted zeolite-bentonite mixtures (ZBMs) and sand-bentonite mixtures (SBMs), which are proposed for use as liner materials. Nevertheless, zeolite is known for its microporous skeleton containing cages and tunnels and it has a great physical affiliation to water uptake. Zeolite and bentonite, in a mixture, are thought to be in competition for water uptake and this may alter the distribution of water content for each soil in the mixture. The present study investigated the suction properties of compacted ZBMs and SBMs for varying mixing ratios and compaction water contents. The soil suction measurement technique chosen was the filter-paper method. The suction characteristics of powdered, granular, and block zeolites, as well as 0, 10, and 20% bentonite in ZBMs and SBMs were measured and compared with each other. Contaminated compacted ZBMs are compared with those of uncontaminated compacted ones at the optimum water content for the 10% and 20% mixtures. The results show that suction capacity of zeolite increases with grain size. As bentonite content increases, both matric and total suction increase for both mixtures. ZBMs have higher matric suction values than SBMs, but not total suction values. Contaminated total suction values are found to be higher than those of uncontaminated samples due to an increase in dissolved ion concentration.

Compaction behavior of synthetic and natural MSW samples in different compositions.

Compaction is the one of the most important stages of the storage process in landfills. Well-compacted municipal solid waste (MSW) occupies less volume than an uncompacted MSW sample of the same weight and provides a safer storage area. The composition of MSW changes in between countries and even cities. For that reason, for effective compaction, the composition effect should be investigated. In this study, effects of composition, degradation and energy on the compaction behavior of artificially-prepared and natural fresh and aged MSW samples were determined. Artificial samples were prepared in representative different compositions Europe (E-1), Turkey (T-1) and the USA (U-1) to examine the effect of the composition. In addition to the synthetic MSW samples, natural MSW samples were obtained from the municipal landfill area of Manisa, Turkey. The standard Proctor test results have shown that the highest maximum dry unit weight was observed with the U-1 composition, which has the lowest organic content and the highest metal content. The degradation effect was investigated on the natural samples. The degraded MSW sample (3-4 years) has significantly higher maximum dry unit weight than the fresh natural MSW sample because of its low organic content. According to the results of this study, with respect to the composition effect, the percentage of organic waste is the most important factor on the compaction behavior of MSWs. As paper, organic and plastic contents increase in the MSW composition the γdry-max value decreases and wopt increases. The ash content does it reversely, as such that any increase in γdry-max decreases the wopt value of the MSW.