Retention Mechanism And Environmental Effects Of Clay-solidified Grouting Curtain To Leachate In Landfill

To prevent seepage of leachate from landfill into environment is one of the most important problems for municipal solid waste (MSW) landfill. Based on the engineering practice and a series of methods including theoretical analysis, laboratory tests, site observation and numerical simulation, the retention mechanism and anti-seepaging capability of clay-solidified grouting curtain (CSGC) to leachate are systematically researched and the environmental effects of CSGC applied in MSW landfill is completely evaluated. The main research contents and results in mis paper are summarized as following:1.Permeability of clay-solidified grouting curtain to leachate. The influence of components and their ratio of grouts, concentration and pH of leachate on permeability are studied with laboratory experiment, and the functional formula of hydraulic conductivity and content of clay and cement is brought up. Then the effects and the characters of CSGC anti-seepage to contaminant such as heavy metals and organic matter are studied.2. Adsorption mechanism and property of clay-solidified grouting curtain to contaminant. In this paper, adsorption is firstly described as a function of CSGC, and the effects of component and their ratio of grouts, leachate environment such as temperature, pH and salinity on adsorption are studied with equilibrium experiment. The evidence shows that the adsorption mechanism of CSGC to contaminant conforming to Freundlich Adsorption Model. It provides the theory for establishing CSGC and utilizing adsorption mechanism.3. Transportation and transformation mechanism of contaminates in clay-solidified grouting curtain and contaminates' transportation features in CSGC. Contaminates in the process of transporting in CSGC and groundwater, of adsorbing, of exchanging, and of transforming willtake place physical, chemical and biological reaction, which makes leachate purified further. Moreover, the features of contaminates' transporting speed, concentration distribution, and contaminates existing form in CSGC are studied.4. Mathematical models and their solutions for hydrodynamic transport of contaminant in clay-solidified grouting curtain. The base formula of transportation that of leachate and contaminant in CSGC and the formula of ground water seepage are put forward. The leachate transport equation with time-varying hydraulic coefficient is established and its mathematical solution is obtained and programmed by finite difference ADI method. By means of mathematical simulation based on the laboratory experiments, the assessment of anti-seepaging and retention effect of leachate seepage and basic parameters describing contaminant transportation and transformation are carried out.5. Longtime environmental effects of clay-solidified grouting curtain applied in MSW landfill. The longtime environmental effects of CSGC controlling leachate anti-seepaging and contaminant are probed systematically at the first time in two aspects of anti-seepaging and purifying, and the durability of CSGC is also studied with experiment in the paper.6. Application of clay-solidified grouting curtain on anti-seepaging engineering in MSW landfill. It has brought great social, economic and environmental benefits in the construction of MSW landfills in Nanchang and Changsha. The application shows that CSGC can meet the design requirement and the sohe poisonous substances well.