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Fang G.,Shenzhen GAD Environmental Technology Co. | Li C.,Shenzhen GAD Environmental Technology Co. | Guifen P.,Shenzhen GAD Environmental Technology Co. | Yijun C.,CAS Wuhan Institute of Rock and Soil Mechanics | And 4 more authors.
Electronic Journal of Geotechnical Engineering | Year: 2015

A three-dimensional axisymmetric model has been established for quantitative description of the gas migration in bioreactor landfills. This model is based on the fluid dynamics and solute transport theories in porous media. Variables like the distribution of gas pressure and the amount of gas collection from the landfilled solid waste can thus be theoretically evaluated. The modeling results were compared with the in-situ monitoring data of the gas output in a field test (experimental region No. III) located at Wuhan Second Princess Hill landfill. Numerical simulation results show that landfill gas pressure distribution differs at different depths, which is closely related to both the structural design of landfill and the distinct degrading properties of the solid waste. Gas output shows a declining trend with the landfill life increases. Gas production in summer is higher than those in other seasons. The reliability and viability of the model were satisfyingly verified by the consistence between the numerical simulation results and field monitoring data. The impact of permeability on the influencing radius of gas pumping well (GPW) and gas production was investigated. Results show that the influencing radius of GPW expanded to 17.8 m from 8.5 m when the inherent permeability increased by 15 m2. Gas production and the influencing radius are obviously affected by the change of the inherent permeability when gas production increased by 27 m3/h. It is mainly because that the gas pressure gradient and transmission pore space increase with the increasing inherent permeability at early stage. But the biodegradation of the solid waste leads to the gradual compaction of the waste and the reduction of porosity with the prolonging buried duration, and thus result in the decrease in the gradients of gas production and the influencing radius of the GPW. These findings could provide significant guideline to the parameterization and design of the gas pumping drainage system in landfills as well as the researches and applications in effective prediction, collection and control of landfill gas. © 2015 ejge.


Hui X.,Yichang Solid Waste Company | Kai L.,Jiangsu Institute of Zoneco Soil Co. | Guofei W.,Jiangsu Institute of Zoneco Soil Co. | Yan W.,Jiangsu Institute of Zoneco Soil Co. | Guifen P.,Shenzhen GAD Environmental Technology Co.
Electronic Journal of Geotechnical Engineering | Year: 2015

A series of chemical immersion tests were conducted, aiming to reveal the leaching characteristics of metallic ions (iron, calcium, and magnesium) in coal gangue under different pH values and temperatures of the chemical solution. The results indicated that the pH value and temperature of the solution both significantly influence the leaching rate and concentration of metallic ions, except iron, in an acidic environment. The stronger the acidity was, the easier the metallic ions leached from the coal gangue. Under the same conditions, the rate and concentration of the metallic ions leached at 80°C were higher than that at room temperature. The results have important significance in pollution prevention and in the control of the soil-groundwater environment around the coal gangue pile, especially in acid rain-prone areas. The results also provide theoretical basis and technical support for the spontaneous combustion control and resource utilization of coal gangue. © 2015 ejge.

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