Destructive testing of polyethylene geomembrane seams: Various methods to evaluate seam strength

The incidence of high-density polyethylene geomembrane liner failures makes it essential that as much information as possible regarding seam performance be extracted from testing. The durability of polyethylene geomembrane seams can be determined largely by the data resulting from conventional seam peel and shear destructive tests.

Unfortunately, current test parameters and acceptance criteria are not used to a great enough extent. Specifically, the seam peel and shear tests can and should be used more fully to assess the effect of seaming on the strength and durability of the seam and the adjacent geomembrane. Specific minimum values for seam shear strength and elongation as well as peel separation should be established by a project's geosynthetic design engineer. In addition, functional seam test acceptance criteria for very low-density polyethylene need to be defined. Another type of testing that can provide valuable information on the aging behavior and defect distribution within field seams is hydrostatic, biaxial burst testing.     

Seaming of geosynthetics

Owners of containment facilities are using geosynthetics at an increased rate. A major concern in their use is the ability to field seam the materials such that the design function of the geosynthetic is transferred through the seam. This paper discusses potential concerns and describes quality assurance techniques that will, when utilized, help ensure that the facility will be constructed according to the design.     

Slope Failures at Yokowatashi and Nagaoka College of Technology Due to the 2004 Niigata-Ken Chuetsu Earthquake and Their Analytical Considerations

Numerous natural or artificially embanked slope failures were caused by the 2004 Niigata-ken Chuetsu Earthquake. Characteristics of large scale natural slope failures that occurred at folding hills, river terraces, etc, were classified from a geometric structural view point. It was noted that surface failures occurred at steep cliffs and landslides occurred at gently slanting dip slopes. The cause of a landslide in a dip slope at Yokowatashi, Ojiya city was analytically investigated based on cyclic shear test results of the laminar sand at the bedding plane. This study revealed that the safety factor of the slope stability became momentarily smaller than 1.0 several times during the earthquake due to the small undrained shear strength of the tuff sand seam and the landslide behavior was simulated by an elasto-plastic dynamic finite element analysis where the strength decrease of the sand seam with increasing number of cycles was taken into consideration. The cause of destructive damage of a school building at Nagaoka National College of Technology (NNCT) was next examined by another elasto-plastic dynamic FEM. From the analysis results, it was confirmed that the building was pulled and twisted by the landslide of the bank shotcrete accompanied with pile fracture.     

Engineering geology investigations of a hazardous-waste landfill in West Central Illinois,USA

Faster-than-predicted pollutant migration at a state-licensed, hazardous-waste landfill was investigated 3 years after its operation was ceased by court order. At that time, the operator of the landfill discovered organic chemicals in a monitoring well during routine sampling, suggesting laekage from the trenches at a rate of 100 to 1000 times faster than predicted by the laboratory tests made for the initial landfill design. To determine the causes for this rapid pollutant migration, investigators studied site geology and stratigraphy, mine subsidence, hydrogeology, condition of waste containers, trench covers, and soil properties. Organic chemical probably leaked when meteoric waters drained freely through the trench covers, flushing liquid wastes from the burial trenches into the permeable, fracture ablation till. Interpretation of aerial photographs was used to find depressions and surface impediments in covers through which the drainage occurred. Pipe-type depressions in covers were probably caused by highly erodible (dispersive) soils. Surface impediments, such as roads and erosion-control dikes, caused runoff to pool over the trench covers. In an attempt to eliminate these problems, the following studies are proposed: geologic studies in exploration and design, field hydrogeologic tests, laboratory tests for highly erodible soils, and postclosure monitoring by photointerpretation and remote sensing.     

Prefabricated bentonite clay liners

The development and use of prefabricated bentonite clay liners is a relatively recent development, even for a technology as young as geosynthetics. There are four currently available commercial products, each of which consists of essentially dry bentonite clay agglomerates (with or without a dry, but water soluble, adhesive) placed on a geotextile or geomembrane carrier layer. Often a covering geotextile is used above the clay, and for two of the products, the entire ‘sandwich’ is needled throughout.

For landfill liner systems, the major use of these materials appears to be as the lower component of a composite primary liner. This use is particularly interesting in the light of response action plans (RAPs) which are being required by many regulating agencies. For landfill closure systems, these materials can readily form the lower component of a composite cap system. Of interest here is their possible capacity to follow subsidence of the landfill and their ability to deform in an out-of-plane manner.

With the newness and potential of prefabricated bentonite clay liners, however, comes a number of questions. This paper attempts to present these questions and the currently available answers regarding the various products. In concludes by giving a number of suggestions and cautions for field placement based on the authors' experiences to date.     

天津双口垃圾填埋场垃圾填埋气体收集、发电及清洁发展机制

《京都议定书》中的一项规定允许加入议定书的工业化国家通过从发展中国家的项目中购买排放配额的方式,来完成他们的减排目标。目前中国天津双口垃圾填埋场正在运用清洁发展机制销售认证减排量。西班牙碳基金的托管方世界银行是减排量的购买方。双口垃圾填埋场于2008年夏季开始运营,通过垃圾填埋收集甲烷,继而将其销售给电网用于发电。向电网销售电力的收入可能不足以判断气体收集和电力设备投资的正确性。通过销售甲烷这种全球变暖潜能值较高的温室气体（其全球变暖潜能是二氧化碳的21倍）产生的认证减排量获取的额外收入,对于气体管理体系实现财务上的可持续非常重要。在没有销售排放抵消的情况下,项目的内部收益率是5．87％,而在销售排放抵消时则为15．23％。在内部收益率较低的情况下,项目将不会被运行。该气体管理项目已由天津清洁能源环境工程有限公司（TCEEE）启动,这是由负责管理垃圾填埋场的天津环卫委员会和天津建设管理委员会共同组建的合资公司。世界银行除了托管西班牙碳基金以外,还是另外11家基金会和机构的托管人。TCEEE选择了一家中国公司-南京长期环境技术发展有限公司作为承建拥有运行转让的承包商,以管理垃圾填埋气体收集和电力系统。     

Speciation analysis of arsenic in landfill leachate

As environmental impacts of landfill last from beginning of cell filling to many years after, there is an increasing interest in monitoring landfill leachate composition especially with regards to metals and metalloids. High-performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) has been applied to the speciation of arsenic in landfill leachates. The difficulty is related to the complexity and heterogeneity of leachate matrices. A soft sample preparation protocol with water dilution and filtration of leachates has proved to be sufficient for the achievement of identification and quantification of arsenic species without matrix effect. The cationic-exchange separation method developed has enabled the detection of six arsenic species (AsIII, MMA, AsV, DMA, AsB, TMAO) in different landfill leachates. The wide range of concentrations of arsenic species (from 0.2 to 250 microg As L(-1)) and their repartition illustrate the high variability of these effluents depending on the nature of the wastes, the landfill management, the climatic conditions and the degradation phase, to list a few. These results provide new information about the chemical composition of these effluents which is useful to better adapt their treatment and to achieve the risk assessment of landfill management.     

生活垃圾填埋场随填埋年龄增长对周边大气环境的影响趋势研究

针对生活垃圾填埋场的主要恶臭污染物NH3、H2S、臭气浓度,以某城市生活垃圾填埋场为例,采用该填埋场自运行至今近10年的历史监测数据进行统计分析.结果表明,随着填埋年龄的增加,厂界处恶臭污染物浓度先增加后降低,在填埋场运行的第5～7年,恶臭污染物浓度达到最大值;通过监测数据和现场调查分析可知,该填埋场对周边800 m以外的村庄影响不明显.     

Analysis of shearing of a rock ridge

A rock ridge carrying a major roadway through a quarry in the greater Chicago, IL area sheared along sub-vertical regional joints causing significant distress of the roadway as a result of apparently limited adjacent quarry excavation of a glory hole. The large-scale movement rendered the road unusable. This paper presents a detailed analysis of factors contributing to this response. Post-event field observations of ridge movement revealed that lateral displacements were concentrated along a horizontal thin shaley seam below the bottom of the quarry. These observations show that the sheared ridge slid along the shaley seam and moved as a single block. Three-dimensional numerical analyses of the ridge and the quarry construction activities show that as the quarry was deepened, a buildup of large horizontal stresses occurred in the rock base above the shaley seam. The excavation of the glory hole through this rock base lead to arching and an increase in longitudinal stresses and a reduction in lateral confining stresses along the ridge. The analyses show how the unique combination of large horizontal stresses, the horizontal shaley seam, and stress redistribution due to glory hole construction lead to large shear displacements along the persistent sub-vertical regional joints.     

Cable-bolting-based semi-mechanised depillaring of a thick coal seam

Based on simple rock mechanics principles, the idea of using a grouted steel rope under tension for supporting a high roof as well as an overlying coal band, and to improve the safe span of overhanging strata near the goaf edge for semi-mechanised depillaring of a thick coal seam standing on pillars was first applied at New Chirimiri Ponri Hill (NCPH) colliery of the Chirimiri area of the South Eastern Coal Field Limited (SECL), India. Taking advantage of the massiveness of the coal seam and pattern of stress redistribution around a depillaring face, field application of this technique made it possible to extract the full thickness (6.5 m) of the No. 3 seam of the colliery (developed along floor with 2.5 m gallery height) in a single lift. The success of this field trial triggered a number of applications of the technique in many other collieries of India due to its technical superiority over the conventional method for underground extraction of thick and developed coal seams. Thus, this paper deals with the efficacy of cable bolting in semi-mechanised depillaring of a thick coal seam as observed at NCPH colliery.     

垃圾填埋场的沉降分析、计算及灰色模型预测

分析了垃圾场的沉降原理,并给出计算方法,应用灰色系统理论,对沉降实际数据进行处理,建立灰色动态GM模型,作出对填埋过程中和封顶后的沉降预测。这对解决城市垃圾填埋场的沉降问题提高垃圾场的潜在处理能力、增加填埋场的有效存贮容量有着十分重大的意义。     

Mechanisms of Leakage through Synthetic Landfill Liner Materials

The introduction of synthetic lining materials for leachate containment and the prevention of groundwater contamination was an important development in landfill technology. These materials have a low hydraulic conductivity which results in minimal leachate release by bulk fluid flow (advection) provided that the barrier (and its construction) is free from defects. However, the effectiveness of these materials as barriers cannot be confirmed unless contaminant release by diffusion is also taken into consideration.
This paper reviews the mechanisms by which transport through barriers occur. It highlights the role of diffusion as a pathway for organic compounds to migrate through synthetic liners and indicates its importance in terms of environmental impact and landfill design.     

Geosynthetic use as daily cover

The application of daily cover material is standard operating procedure at most solid waste landfills. Traditionally, daily cover consists of a soil layer applied over the active working face. Since landfill airspace has become more scarce, there has been a heightened interest in recovering the airspace displaced by the daily cover. Waste Management of North America, Inc., has been evaluating geosynthetics for use as substitutes for soil daily cover. Due to their satisfactory performance, negligible airspace displacement, simple operation, and their relatively low price, geosynthetic materials are an attractive alternative to soil for daily cover. This paper presents a discussion of the purpose of daily cover along with an outline of the types of geosynthetics evaluated and the operational procedures involved in their use. The paper also presents a major conclusion that alternative materials, such as geosynthetics, should be allowed by regulatory agencies if they can meet performance criteria.     

垃圾填埋场边坡稳定安全监测指标及警戒值

随着垃圾的产量和填埋量迅速增加,垃圾堆体的稳定问题日益突出,填埋场运行中安全监测显得十分重要。针对某大型垃圾填埋场失稳事件,对该填埋场堆体边坡开展了近2年的监测,获得了各种气象条件下渗滤液水位、地表水平位移、竖向位移、深层侧向变形等监测数据,特别是2008年6月强降雨期间垃圾堆体边坡局部失稳和2009年2月污泥坑周边堆体滑移过程中完整、全面的监测数据。基于监测数据,并结合实际降雨条件、填埋场运行状况,对填埋场失稳的内在因素进行详细的分析,得出渗滤液水位过高是导致堆体边坡失稳的主要内因,水平位移速率是填埋场边坡稳定状态最为敏感的指标。最后 根据监测数据 进行统计分析 ,提出垃圾填埋场稳定安全监测关键指标及警戒值, 为今后垃圾填埋场的现场监测工作提供重要依据 。     

Removal of non-biodegradable organic matter from landfill leachates by adsorption

Leachates produced at the La Zoreda landfill in Asturias, Spain, were recirculated through a simulated landfill pilot plant. Prior to recirculation, three loads of different amounts of Municipal Solid Waste (MSW) were added to the plant, forming in this way consecutive layers. When anaerobic digestion was almost completed, the leachates from the landfill were recirculated. After recirculation, a new load of MSW was added and two new recirculations were carried out. The organic load of the three landfill leachates recirculated through the anaerobic pilot plant decreased from initial values of 5108, 3782 and 2560 mg/l to values of between 1500 and 1600 mg/l. Despite achieving reductions in the organic load of the leachate, a residual organic load still remained that was composed of non-biodegradable organic constituents such as humic substances. Similar values of the chemical oxygen demand (COD) were obtained when the landfill leachate was treated by a pressurised anoxic-aerobic process followed by ultrafiltration. After recirculation through the pilot plant, physico-chemical treatment was carried out to reduce the COD of the leachate. The pH of the leachate was decreased to a value of 1.5 to precipitate the humic fraction, obtaining a reduction in COD of about 13.5%. The supernatant liquid was treated with activated carbon and different resins, XAD-8, XAD-4 and IR-120. Activated carbon presented the highest adsorption capacities, obtaining COD values for the treated leachate in the order of 200mg/l. Similar results were obtained when treating with activated carbon, the leachate from the biological treatment plant at the La Zoreda landfill; in this case without decreasing the pH.     

Relationship between joint movement and mining subsidence

The hazards associated with the possible collapse of old mine workings underlying an active landfill site in north-east England have been identified as a significant concern to both the regulatory authorities and to the landfill operator. A quantitative assessment of the hazards and their perceived risks to the integrity of the composite lining system in place beneath the landfill has been undertaken using a combination of field observation, established mine subsidence prediction tools and numerical modelling techniques. Field observations have identified the presence of extensive fissuring within the limestone underlying the site, however, it is difficult to assess the extent to which mining has contributed to the development of these features. In light of this, an influence function technique has been used to attempt to predict the degree of fracturing that could have been experienced at the surface due solely to mining, with the intention of illustrating whether the scale of movements on pre-existing joints could be attributed to mining subsidence. The results of this analysis have subsequently been used within a finite-difference numerical model to assess the effect that a fracture of the scale predicted would have on the composite lining system.     

Diversion of the River Calder at Welbeck: An Engineering and Environmental Challenge

The Welbeck reclamation and landfill project (near Wakefield) is reclaiming over 1.5 km² of former aggregate and colliery workings through the creation of a new landform. This is to incorporate millions of tonnes of colliery spoil and controlled (i.e. household, trade) wastes, and to avoid the need for disposal on less suitable sites elsewhere.
The scheme is already under way, but the proposed diversion of the River Calder to one side of the site would more than double its capacity for landfill. In environmental terms, the project has been seen as the creation of a new river corridor, rather than simply the diversion of a river channel.
The paper outlines the engineering of the river diversion, which is routed for about 2 km through varied and difficult ground conditions, and gives a number of examples of the priority attached to landscape and after-use factors, and their intrinsic importance in design.     

Landfill site selection utilizing TOPSIS methodology and clay liner geotechnical characterization: a case study for Ankara,Turkey

The purpose of this study was to select alternative landfill sites for Ankara based on the growing trends of Ankara toward the Gölba?? municipality, and to eventually select the best alternative through the use of decision-making tools. Geographic information systems (GIS) and multi-criteria decision analyses were employed to perform landfill site selection. Several criteria, including geology, slope, proximity to roads, availability and proximity of landfill containment material, settlement, suitability for agriculture, vegetation cover, erosion, and lineament system were gathered in a GIS environment. A weight value was assigned to each criterion by applying the pairwise comparison method and the analytical hierarchy method. An ideal point method, namely, the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) was applied to choose the best alternative landfill site. The geotechnical properties of “Ankara clay”, which shows widespread distribution in Ankara, were reviewed and assessed for the clay's suitability as a single, compacted clay liner and as a component of a geomembrane-compacted clay composite liner for the alternative landfill site selected. The HELP model was employed in order to determine the cumulative, mean leachate head and cumulative, unitized expected leakage rate amounts through the landfill. Four different profiles, from the least conservative to the most conservative, were created and analyzed.     

Subsidence performance of landfills

This paper presents field measurements of landfill subsidence for five municipal solid waste landfills. Data from the.five sites are within the range of landfill subsidence reported in other publications.

At one site with variable subsidence of up to 10 percent of the landfill height in 3 years after capping, portions of an in-situ HDPE cap geomembrane were uncovered. The geomembrane showed no visual signs of subsidence-induced distress.     

垃圾填埋场衬垫土壤材料对Cr(Ⅵ)的吸附特性研究

通过静态平衡吸附试验对采用颗粒活性炭及酸活化膨润土改良的垃圾填埋场衬垫土壤材料吸附重金属的特性进行了观察。试验结果表明:研究中的所有土壤样本对Cr(Ⅵ)的吸附属于非线性的Langmuir模式。经颗粒活性炭及酸活化膨润土改良的衬垫土壤材料与天然黏土材料相比,对Cr(Ⅵ)的吸附强度有了很大的提高,说明颗粒活性炭和酸活化膨润土可以作为改良衬垫土壤的材料去吸附重金属。所有土壤样本对Cr(Ⅵ)的吸附量均随着温度的升高而增大,随着土壤固体颗粒浓度的增大而减小。Langmuir等温参数(qm,b)随着土壤固体颗粒浓度的增大而呈对数性减小,但随着土壤固体颗粒浓度进一步增大到某一临界值(例如200 g/L),其值基本稳定了,另外等温参数也随着温度的升高呈线性增大的趋势。由试验结果可以得出,采用较低的土壤固体颗粒浓度所确定的吸附参数值不适合模拟实际工程条件,其值将引起对垃圾填埋场衬垫的迟滞因子作出过高估计。因此,为了获得与实际工程条件比较接近的吸附参数值,静态平衡吸附试验必须在一个充分大的固体颗粒浓度条件下进行。