Environmental assessment of an uncontrolled sanitary landfill,Pocos de Caldas,Brazil

There are more than 20,000 uncontrolled sanitary landfill areas in Brazil. The paper reports an integrated study undertaken to develop an environmental assessment of the uncontrolled sanitary landfill area of the city of Po?os de Caldas, State of Minas Gerais, Brazil. A number of remedial alternatives were evaluated. The USGS modular 3D finite difference groundwater flow model (Modflow) and Modular 3D Finite Difference Mass Transport Model (MT3D) software were used to simulate groundwater flow and contaminant transport modelling, as well as to predict changes due to the proposed remediation measures. The remedial alternatives considered for normal conditions from 20 to 40 year periods were waste removal, vertical cut-off barriers, extraction wells and top capping. The results indicated that extraction wells and waste removal are the best alternatives because they significantly reduce both the extension and levels of the contamination plume even after 5 years. The extraction well proved a less expensive remedial alternative than waste removal.      

Seismic displacements of landfills and deformation of geosynthetics due to base sliding

Seismic design of waste landfills has been a subject of intense research over the past two decades, primarily due to the severe environmental impact of a potential failure. The majority of the related studies have been focused on the stability assessment of landfills utilizing permanent deformation methods. However, previous investigations have not fully addressed the impact of the composite liner system on the seismic performance of the geostructure, mainly expressed as potential sliding development, which is greatly affected by the geometry and the resulting initial static stress state of the landfill. Therefore, the aforementioned issues are investigated via a detailed parametric study, where the dynamic behaviour of the composite liner system is examined both analytically and numerically. The conducted coupled analyses indicated that the most significant parameters of the complex dynamic response of waste landfills can be reduced in two ratios that comprise functions of the main characteristics of the geostructure and of the excitation. Moreover, two distinct failure patterns have been identified with respect to the characteristics of the distribution of the permanent displacements along the interface and the axial deformation along the geosynthetic. The occurrence conditions of these failure patterns can be determined in terms of the two abovementioned ratios as verified by the analytical results of the critical acceleration of a simple SDOF system.     

多头水泥土搅拌桩在填埋场防渗中应用

结合江苏省泰州市生活垃圾卫生填埋场的垂直防渗系统多头水泥土搅拌桩的施工,阐述了多头水泥土搅拌桩的施工原理、施工工艺、技术要求、质量控制和防渗效果的检测。工程实践表明:多头水泥土搅拌桩具有施工效率高、造价低、施工方便和垂直防渗效果好等优点。     

设垃圾坝填埋场的三楔体滑动分析

 提出新建及扩建设垃圾坝填埋场的三楔体极限平衡分析法，给出安全系数的近似解，使得填埋场沿背部、底部及垃圾坝内坡处衬垫界面的三折线型滑动分析大为简化，发现其具有较好的工程适用性。该方法与精度较高的Spencer法所给出的计算结果吻合良好，且能考虑填埋体内摩擦角的影响。研究结果显示，衬垫界面的强度直接影响填埋体沿衬垫界面的稳定性，而填埋场各坡坡度、填埋场高度和宽度以及垃圾坝的高度对安全系数均有较大的影响。对扩建填埋场的分析结果表明，扩建填埋体沿新老场交界面的安全系数较低，在扩建填埋场的设计中应引起重视。另外，扩建填埋场的横向扩建宽度越大，则其界面安全稳定性越好。     

Hydraulic conductivity of GCLs in MSW landfills

The state of the art of the study on the hydraulic conductivity of GCLs is presented in terms of the influence of the effective stress,chemical interactions,freeze-thaw cycles and temperature gradients.The changes of void ratio caused by changes of effective stress have a direct linear effect on the hydraulic conductivity,regardless of the cation concentration or the thickness of the adsorbed layer.The hydraulic conductivity is related to the relative abundance of monovalent and divalent cation（RMD）,and RMD has a great effect on the hydraulic conductivity in weak solution.The long-term susceptibility of GCLs to increased hydraulic conductivity as a response to repeated freeze-thaw cycling is minimal,which has been proved after 150 freeze-thaw cycles.The potential of desiccation cracking increases with the increasing temperature gradient and is related to the initial subsoil water content,the applied overburden stress,etc.     

Limit equilibrium analysis of translational failure of landfills under different leachate buildup conditions

Excessive leachate levels in landfills can be a major triggering mechanism for translational failure. The scope of this paper is to present the development of the calculation methods for limit equilibrium analysis of translational failure of landfills and the effects of parametric variation on the factor of safety （FS） of landfills under different leachate buildup conditions. During the development of the calculation methods, 4 leachate buildup conditions are considered. The FS for an interface with high friction angle and low apparent cohesion generally drops much more quickly when leachate levels are increased than that for an interface under inverse conditions. The critical interface of a multilayer liner system with the lowest FS for the entire waste mass can shift from one to another with changes in the leachate levels. The different interfaces of a multilayer liner will have different FS-values under different leachate buildup conditions.     

Computer Simulations that Illustrate the Heat Balance of Landfills

The characterization of landfills with respect to geometry, temperature, gas flow, water content, and heat generation yields important information about landfill activity and possible risks; insufficient or defective surface sealing, for example, can lead to increased biogas release or to local overheating. The aim of this work was to develop a model in order to simulate the thermal behavior of landfills. The most important variables of interest have been identified, in order to make recommendations for the completion of existing landfills. Furthermore, sealed landfills requiring action regarding the temperature development can be studied. Simulations thus offer the possibility to identify causes and make proposals for solutions. Heat transport within the landfill can be described by the model developed in this work. The maximum temperatures predicted in the center of the landfill are in the range of values measured on different landfills up to 353 K. The interaction with gas flow gives good results, too. A temperature rise of some kelvin between the leak surface site and surrounding surface parts was determined, in agreement with measurements.Paper presented at the Sixteenth European Conference on Thermophysical Properties, September 1-4, 2002, London, United Kingdom     

用于垃圾填埋场防护与排水的非织造土工布的耐化学性研究

采用在韩国垃圾填埋中常用的涤纶 (再生或不可再生 )非织造土工布、丙纶非织造土工布和复合土工布等 8种材料作为测试样本 ,运用修正的EPA90 90测试方法在pH值分别为 3、8、12的溶液和垃圾沥出液中比较了不同材料的化学稳定性。     

垃圾填埋场封顶系统的设计与水分平衡

为了解决传统压实黏土封顶系统在干旱及半干旱地区存在干燥开裂的问题,三种新型的ET（Evapotranspiration）封顶系统的设计方案被提出了。其中,一种ET封顶系统设计方案的结构由上下各1m厚的植物生长土层和阻隔土层构成,另外两种ET封顶系统分别在中间与底部增设了一层生物阻隔层。在考虑降水与蒸发蒸腾循环补给的条件下,建立了水汽在多层非饱和土壤中迁移的一维数学模型。以1976年大连市全年的降水与蒸发蒸腾强度为边界条件,模拟了水汽在四种封顶系统中的迁移规律。计算结果表明,在传统压实黏土封顶系统中,由于压实黏土层具有极低的渗透性,致使整层土壤不能得到有效的水分补给;ET封顶系统中整个土层可以在降水的过程中有效地从边界得到补给,同时在蒸发蒸腾的条件下,把土层中的储水释放;ET封顶系统设计方案2中设置的生物阻隔层,不仅可以防止生物对阻隔土壤层的破坏,而且起到了排水作用。     

考虑生物降解的填埋场封场后沉降分析模型

探讨了生物降解在封场后填埋场沉降中的作用，揭示了填埋体组成及颗粒密度对填埋场沉降
的影响。提出了填埋场的最终降解沉降率取决于降解速率与填埋时间的乘积以及填埋体的可降解有机质的
体积分数，修正了填埋场封场后的沉降分析模型。提出了“限制拟合”的概念，改进了拟合填埋场沉降曲
线的方法，并利用沉降观测曲线进一步修正预测结果。利用提出的模型拟合了7个填埋场的13条沉降曲线
，结果表明该模型能够较好地估算填埋场的封场后沉降。