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The composition of municipal solid waste (MSW) in the Cairo metropolitan area is investigated. The outputs of MSW sorting analysis at various locations in Cairo with different waste management schemes are presented. Organics (58–75%) and plastic waste (19–28%) are the main components of MSW in Cairo with a higher percentage of organics in landfills compared to dumpsites. The leachate quality is analyzed, and the analysis results indicate that the concentration of macro inorganic pollutants (NH4+, Na+, Ca2+, and Cl−) and heavy metals (e.g., Cd2+ and Zn2+) are exceeding the majority of values reported in the literature in various cities all over the world. There was no evidence of an effect of the recycling process on chloride concentration in leachate, while the concentration of iron was reduced. The variation of leachate quality with time for two samples collected from the same municipal solid waste landfill is presented. The first leachate sample is a two-year-old, and the second sample is a sixteen-year-old. There was a significant increase in the concentration of chloride, sodium, chromium, calcium, and magnesium. The implications of the leachate quality in Cairo on the longevity of barrier systems in an MSW landfill are discussed.

The influence of discrete and randomly distributed polyester (PET) fibers in improving the crack resistance and water-tightness of clay barriers was studied by conducting a series of centrifuge model tests at 40 gravities using a large beam centrifuge available at Indian Institute of Technology Bombay. Model clay barriers with and without fibers were subjected to flexural distress by inducing differential settlements using a settlement simulator. Two types of clay barriers were prepared by using two different types of soil, namely bentonite amended silty soil (Soil A) and kaolin clay-sand mixture (Soil B). Digital image cross-correlation (DIC) technique was used for analyzing the images captured by a digital photo camera and a charged couple device (CCD) camera, mounted along with the model. Unreinforced soil barriers (URSB) were found to lose their water-tightness and integrity at relatively lower distortion levels compared to identical fiber reinforced soil barriers (FRSB). Also, the performance of URSB and FRSB was found to be superior for Soil A compared to Soil B. The capability of PET fibers on preservation of existing unreinforced soil barriers was also demonstrated. The strain at crack initiation, epsilon(c), for FRSB is 2.90 and 2.36 times higher than identical URSB for Soil A and Soil B, respectively. Similarly, the strain at the onset of water breakthrough, epsilon(b), for FRSB is 2.14 and 2.79 times higher than identical URSB for Soil A and Soil B, respectively. There is a significant influence of fiber inclusion in retarding the crack initiation and water breakthrough at the onset of flexural distress for both the soil types. Thus, FRSB can withstand more distortion and strain while maintaining the integrity of the clay barrier. This observed behaviour of restraining cracks and improved performance of FRSB is primarily due to the reinforcement effect achieved due to soil-fiber interactions. (C) 2016 Elsevier B.V. All rights reserved.

OLEDs and organic photovoltaic (OPV) devices require encapsulation from water vapor using a permeation barrier system. As a benchmark for barrier quality, often only a single number is provided as water vapor transmission rate. However, this value is highly dependent on the aging climate. So far, little scientific effort has been undertaken to characterize ultrahigh moisture barriers at different temperatures and relative humidities. We present Ca-test studies on sputtered Zinc-Tin-Oxide and atomic layer deposited AlOx barriers in extensively varied climates. Relative humidities are changed at constant temperatures, and temperatures are changed at constant absolute humidity. We find Henry's law to apply for sorption and discover a fundamental change of the diffusion regime with time related to the interface between the test and the barrier thin-film.

Clay-based landfill covers often have a geomembrane (GM) layer sandwiching between the clay barrier and the cover soil. The knowledge pertaining to the deformation behaviour of a clay barrier along with geomembrane subjected to differential settlements is very limited. Hence, the main objective of this paper is to examine the influence of GM on the integrity of clay-based landfill covers subjected to differential settlements in a geotechnical centrifuge. First, scaling considerations required for modelling geomembrane in a centrifuge are presented. A series of centrifuge tests were performed at 40 gravities using a 4.5 m radius beam centrifuge having a capacity of 2500 g-kN available at IIT Bombay on model clay-based landfill covers with and without GM. By maintaining type moist-compacted conditions of the clay barrier as constant, the thickness of the clay barrier was varied as 0.6 m and 1 m. The performance of the clay barrier with and without GM was monitored by measuring water breakthrough at the onset of differential settlements. The analysis and interpretation of centrifuge test results reveal that with the provision of a GM and an overburden pressure equivalent to that of a landfill cover, the sealing efficiency of the cover system was found to be maintained even after the formation of full-depth cracks within 0.6 m and 1 m thick clay barriers subjected to a maximum distortion level of 0.125. This observed behaviour is attributed to the downward thrust exerted by the deformed geomembrane at the zone of maximum curvature which hinders the infiltration of water through cracks. This indicates the significant influence of GM in maintaining the sealing efficiency of a landfill cover system. (C) 2012 Elsevier Ltd. All rights reserved.

Geological disposal of the spent nuclear fuel often uses the concept of multiple barrier systems. In order to predict the performance of these barriers, mathematical models have been developed, verified and validated against analytical solutions, laboratory tests and field experiments within the international DECOVALEX III project. These models in general consider the full coupling of thermal (T), hydraulic (H) and mechanical (M) processes that would prevail in the geological media around the repository. For Bench Mark Test no. 1 (BMT1) of the DECOVALEX III project, seven multinational research teams studied the implications of coupled THM processes on the safety of a hypothetical nuclear waste repository at the near-field and are presented in three accompanying papers in this issue. This paper is the first of the three companion papers, which provides the conceptualization and characterization of the BMT1 as well as some general conclusions based on the findings of the numerical studies. It also shows the process of building confidence in the mathematical models by calibration with a reference T-H-M experiment with realistic rock mass conditions and bentonite properties and measured outputs of thermal, hydraulic and mechanical variables. © 2005 Elsevier Ltd. All rights reserved.

The present work analyses silicon oxide coated polyester films, with attention paid to the effect of substrate process additives on the coating defect population, and on the coated film mechanical properties. The defect population is characterized by means of reactive ion etching, and the mechanical properties are determined from the analysis of uniaxial fragmentation tests. The coating crack onset strain is decreased by the presence of substrate additives, due to a broadening of the Weibull defect distribution. Moreover, finite element analysis of stress concentrations resulting from additive-induced roughness shows that local stress concentrations are negligible. It is the critical defects, such as microcracks that are the most detrimental to the coating effective cohesive properties.