A simplified analytical model for run-out prediction of flow slides in municipal solid waste landfills

Flow slides in municipal solid waste (MSW) landfills are common geoenvironmental issues in the urban environment and can pose a serious threat to the surrounding population and infrastructure. Prediction of the maximum run-out distance of flow slides in MSW landfills is therefore an essential part of hazard and risk assessment in engineering design. Based on the framework for simple analysis originally developed by Hungr (1995), we propose a simplified analytical model for calculating dam breaks in a plastic fluid along a single inclined base. In the proposed model, a quarter-elliptical shape is used to describe the approximate configuration of the flow slide. Following this step, the physical laws relating to the conservation of mass and energy are used to calculate the potential flow. Of additional note is a boundary condition in mathematics relating to this simplified analytical model, which is also reported in this study. Taking the obvious mobility characteristics of the MSW at point of failure into consideration, a three-phase simplified model along double inclined bases has been further developed for run-out prediction of the flow slide in MSW landfill. The proposed three-phase model is then applied to estimate the maximum run-out distance of two typical flow failures of landfills located in Sarajevo and Bandung, which demonstrate the capability of the proposed simplified analytical model for use in hazard assessments of landfills.     

Comparative study of municipal solid waste treatment technologies using life cycle assessment method

The aim of the study is to analyze three different waste treatment technologies by life cycle assessment tool. Sanitary Landfill, Incineration and gasification-pyrolysis of the waste treatment technologies are studied in SimaPro software based on input-output materials flow. SimaPro software has been applied for analyzing environmental burden by different impact categories. All technologies are favorable to abiotic and ozone layer depletion due to energy recovery from the waste treatment facilities. Sanitary landfill has the significantly lower environmental impact among other thermal treatment while gases are used for fuel with control emission environment. However, sanitary landfill has significant impact on photochemical oxidation, global warming and acidification. Among thermal technology, pyrolysis-gasification is comparatively more favorable to environment than incineration in global warming, acidification, eutrophication and eco-toxicity categories. Landfill with energy recovery facilities is environmentally favorable. However, due to large land requirement, difficult emission control system and long time span, restriction on land filling is applying more in the developed countries. Pyrolysis-gasification is more environmental friendly technology than incineration due to higher energy recovery efficiency. Life cycle assessment is an effective tool to analyze waste treatment technology based on environmental performances.     

Stabilization of desert sands using municipal solid waste incinerator ash

This paper presents experimental results on the use of incinerator ash in stabilizing desert sands for possible use in geotechnical engineering applications. The incinerator ash was added in percentages of 2, 4, 8, 10 and 12%, by dry weight of sand. Laboratory tests such as compaction, unconfined compression, shear box and hydraulic conductivity were performed to measure the engineering characteristics of the stabilized material. The results showed substantial improvements in unconfined compressive strength and shear strength parameters (c and φ). Thus, incinerator ash can be used to improve the shear strength characteristics of desert sands. The permeability of the sand–incinerator ash mixture was relatively low.     

Geoenvironmental site investigation using different techniques in a municipal solid waste disposal site in Brazil

Different geoenvironmental site investigation techniques to assess contamination from a municipal solid waste disposal site in Brazil are presented here. Superficial geophysical investigation (geoelectrical survey), resistivity piezocone penetration tests (RCPTU), soil samples collected with direct-push samplers and water samples collected from monitoring wells were applied in this study. The application of the geoelectrical method was indispensable to identify the presence and flow direction of contamination plumes (leachate) as well as to indicate the most suitable locations for RCPTU tests and soil and water sampling. Chemical analyses of groundwater samples contributed to a better understanding of the flow of the contaminated plume. The piezocone presented some limitations for tropical soils, since the groundwater level is sometimes deeper than the layer which is impenetrable to the cone, and the soil genesis and unsaturated conditions affect soil behavior. The combined interpretation of geoelectrical measurements and soil and water samplings underpinned the interpretation of RCPTU tests. The interpretation of all the test results indicates that the contamination plume has already overreached the landfill’s west-northwest borders. Geoenvironmental laboratory test results suggest that contamination from the solid waste disposal site has been developing gradually, indicating the need for continuous monitoring of the groundwater.     

垃圾土蠕变-降解特性的室内试验研究

通过室内蠕变-降解对比试验,研究了城市固体废弃物（MSW）的长期变形过程,详细地分析了MSW应变、沉降速率以及孔隙比随时间的变化规律。试验结果显示,考虑有机物降解情况下沉降速率与时间在双对数坐标下呈线性关系;不同的生物降解条件下MSW的变形特性表现出不同的规律。研究表明,MSW的蠕变变形是应力与有机物生物降解耦合作用的结果,采用室内蠕变-降解试验可以很好地模拟垃圾土的沉降变形过程,为室内进一步研究垃圾土的蠕变降解特性提供了很好的依据。     

城市固体垃圾填埋场不均匀沉降分析

老垃圾填埋场竖向扩建时垃圾堆体的不均匀沉降控制是中间防渗衬垫系统设计的基础,正确计算和分析垃圾堆体的不均匀沉降将是老填埋场竖向扩建时成功与否的关键。研究了竖向扩建时垃圾不均匀沉降,并介绍了不均匀沉降的计算方 法,结合工程实例对老填埋场竖向扩建时垃圾不均匀沉降影响进行了分析,从工程技术角度提出了相应的解决方案。     

Petrogenesis of municipal solid waste combustion bottom ash

A petrographic study was conducted on a suite of bottom ash particles from 3 different modern municipal solid waste combustors. The object of the study was to evaluate the mineralogical characteristics and formation process of the bottom ash by using standard geological techniques of light microscopy, electron microscopy, and X-ray microanalysis. This information was subsequently used to model the bottom ash petrogenesis based upon an examination of the mineralogy, melt structure, and composition of the ash.Bottom ash can be divided into two major groups: 1) refractory waste products and 2) melt products. The refractory waste products consist largely of rock and mineral fragments, various waste metals, and unmelted glass shards. The melt products consist of two distinct glasses: 1) isotropic glass, and 2) opaque glass. Complex silicate minerals are precipitated from and are abundant in the isotropic glass whereas both metal oxide and silicate minerals are precipitated from the opaque glass.The isotropic and opaque glasses formed simultaneously in different locations on the combustor grate. The contrast in melting (liquidus) temperatures shown by these glasses suggests that the isotropic melts were produced at localized hot spots (1500°C to 1650°C) and the opaque melts formed at cold spots (1150°C to 1400°C) on the grate. This could be the result of heterogeneous distribution of combustible municipal solid waste on the grate or from localized hot spots where air is introduced through the grates. In some instances the two glasses then had the opportunity to variably mix with each other. Fe-oxides represent waste metal fragments that were assimilated by melting and later recrystallized.Bottom ash is produced via a co-mingled two melt system that forms melilite-bearing, alkaline, volcanic-like rocks. The great similarity of the bottom ash residues between these 3 different MSW combustors suggests that, despite variable combustor designs and heterogeneous waste feed, high temperature combustion of MSW produces bottom ash of fairly uniform composition and structure that formed via the petrogenetic process described above. Alterations to the combustion process or implementations of secondary treatment technologies may render the bottom ash residue into a more environmentally stable material better suited for aggregate or long term secure disposal in landfills.     

Geophysical imaging of municipal solid waste contaminant pathways

Surface electrical and electromagnetic surveys were conducted on top of a solid waste facility in Unguwan Dosa, Kaduna State, Northwest Nigeria. The aim of the geophysical survey was to detect vertical and subvertical fractures that may provide pathways for groundwater and contaminant transport. Results from the 2D electrical resistivity imaging showed vertical and subvertical contacts overlain by 6–10 m thick overburden. Quantitative interpretation of the VLF-EM data correlates well with the results of the 2D resistivity imaging delineating the vertical and subvertical contacts as good and weak conductors (fractures zones) with resistivity values of 40–220 and 300–420 Ω m, respectively. Azimuthal Schlumberger VES measurements yield apparent anisotropy values ranging from 1.01 to 1.47 for electrode spacings of 1–45 m with the highest value recorded at spacing of 2 m. However, azimuthal variations at large spacings (30–45 m) showed no fracture anisotropy due possibly to the array’s low sensitivity to anisotropy at these spacings. The result of the study showed that pollutants in the leachate can reach and contaminate the groundwater. Therefore, urgency for leachate treatment at this site is recommended to prevent contamination of groundwater.     

Site selection in municipal solid waste management with extended VIKOR method under fuzzy environment

Nowadays, selection of the suitable disposal site in municipal solid waste (MSW) management has become a challenge task for the municipal authorities, especially in fast-growing areas. Site selection can be viewed as a complicated multi-criteria decision-making (MCDM) problem requiring consideration of multiple alternative solutions and conflicting quantitative and qualitative criteria. In this paper, linguistic variables, which can be expressed as trapezoidal fuzzy numbers, are used to assess the ratings and weights for the selection criteria. The ordered weighted averaging operator is utilized to transform the fuzzy decision matrix into crisp values considering the decision maker’s attitudinal character. For selecting the best site, the extended VIsekriterijumska optimizacija i KOmpromisno Resenje (VIKOR) method is applied to determine the priority ranking of alternatives. As a result, a hierarchy MCDM model based on fuzzy set theory and VIKOR method is proposed to deal with the site selection problems in the MSW management system. An empirical study in Shanghai, China, is provided and comparison with the existing approach is conducted to illustrate the applicability and benefits of the proposed method.     

考虑龄期分层的固体废弃物填埋场边坡稳定分析

固体废弃物填埋场长期使用过程中,垃圾土的强度参数随着龄期的变化而变化。在进行固体废弃物填埋场边坡稳定分析时考虑按龄期分层,基于极限分析上限理论,提出了转动-平动组合和多块体平动两种破坏机构。通过水平分层土坡算例的对比分析,验证两种破坏机构的合理性和有效性。进而对填埋场算例按龄期分层分析,结果表明,极限分析上限解的安全系数和破坏机制与强度折减有限单元法非常接近,多块体平动机构通过随机搜索所得的最危险滑裂面优于转动-平动组合机构。最后分析西班牙Coll Cardús固废填埋场,此填埋场是按龄期分层的典型复杂填埋场,运用两种破坏机构所得的安全系数和最危险滑裂面与有限单元法相符。算例分析表明,在不考虑水位的情况下,填埋体堆填时间越长越有利于填埋场的稳定。当填埋体按低、中、高龄期分层形成时,填埋场的整体稳定安全系数介于中龄期和高龄期的均质边坡之间。     

垃圾填埋场抽水试验及降水方案设计

垃圾填埋场中的渗滤液水位过高会引发一系列环境和稳定问题,工程上可用竖井抽水降低渗滤液水位。通过在填埋场现场进行抽水试验,确定垃圾土的渗透系数和抽水影响半径,在此基础上对填埋场降水的瞬态流问题进行有限元模拟,分析了抽水井口径和间距对填埋场降水的影响,提出了降水方案的设计步骤和方法。抽水试验表明,现场垃圾的渗透系数约为3.6×10-4cm/s,抽水影响半径约为20m。数值分析表明,井径的变化对于降水效果影响不大,而合理选择抽水井间距对降水十分关键。进行抽水方案设计时,应首先根据工期和降水幅度要求计算井间距,按井的出水速度选择水泵,再根据水泵确定井径,最后根据井径和过滤层形式确定钻孔尺寸并选择钻机。     

Modeling elasto-visco-bio-plastic mechanical behavior of municipal solid waste in landfills

Acta Geotechnica - This paper presents a mechanical model for the prediction of short-term and long-term settlement of municipal solid waste in landfills. The load-induced volumetric compression,...     

城市生活垃圾生态填埋技术研究概况和进展

对城市生活垃圾生态填埋技术的发展概况及研究进展进行了综述,包括生态填埋技术的概念、意义、现状和发展趋势,并提出了目前该领域研究中需重点研究的课题和一些新的思路。     

Quantitative physical model of vulnerability of buildings to urban flow slides in construction solid waste landfills: a case study of the 2015 Shenzhen flow slide

Natural Hazards - A new type of artificial slope, namely the construction solid waste (CSW) landfill, is being built around cities to dispose of waste. These artificial slopes pose risks to...     

Permeability and compression characteristics of municipal solid waste samples

Four series of laboratory tests were conducted to evaluate the permeability and compression characteristics of municipal solid waste (MSW) samples. While the two series of tests were conducted using a conventional small-scale consolidometer, the two others were conducted in a large-scale consolidometer specially constructed for this study. In each consolidometer, the MSW samples were tested at two different moisture contents, i.e., original moisture content and field capacity. A scale effect between the two consolidometers with different sizes was investigated. The tests were carried out on samples reconsolidated to pressures of 123, 246, and 369 kPa. Time settlement data gathered from each load increment were employed to plot strain versus log-time graphs. The data acquired from the compression tests were used to back calculate primary and secondary compression indices. The consolidometers were later adapted for permeability experiments. The values of indices and the coefficient of compressibility for the MSW samples tested were within a relatively narrow range despite the size of the consolidometer and the different moisture contents of the specimens tested. The values of the coefficient of permeability were within a band of two orders of magnitude (10⁻⁶–10⁻⁴ m/s). The data presented in this paper agreed very well with the data reported by previous researchers. It was concluded that the scale effect in the compression behavior was significant. However, there was usually no linear relationship between the results obtained in the tests.     

Shear strength of municipal solid waste for stability analyses

This paper investigates the shear strength of municipal solid waste (MSW) using the back analysis of failed waste slopes as well as field and laboratory test results. Shear strength of MSW is a function of many factors such as waste type, composition, compaction, daily cover, moisture conditions, age, decomposition, overburden pressure, etc. These factors together with non-standardized sampling methods, insufficient sample size to be representative of in situ conditions, and limited shear displacement or axial strain imposed during the laboratory shear testing have created considerable scatter in reported results. Based on the data presented herein, large shear displacements are required to mobilize the peak shear strength of MSW which can lead to displacement incompatibility between MSW and the underlying material(s) such as geosynthetic interfaces and foundation soils. The data presented herein are used to develop displacement compatible shear strength parameters for MSW. Recommendations are presented for modeling the displacement and stress dependent strength envelope in stability analyses.     

城市固体废弃物填埋场的岩土工程问题

论述了国内外城市卫生填埋场相关的岩土工程问题及其研究现状,包括卫生填埋场填埋体物理力学性质、卫生填埋场的防渗系统和边坡稳定等一系列岩土工程问题,在此基础上初步探讨了我国城市卫生填埋场相关岩土工程问题的发展前景。     

Analyses on a high leachate mound in a landfill of municipal solid waste in China

The leachate levels in the landfills in southern China are generally high. Field monitoring was carried out in the Suzhou landfill to investigate the leachate mound. The saturated hydraulic conductivity and soil–water characteristic curve (SWCC) of municipal solid waste were measured using samples taken from different depths of the landfill. Field monitoring reveals that a perched leachate mound and a substantial main leachate mound existed in the landfill. The saturated hydraulic conductivities of wastes in shallow, middle and deep depth were measured to be 4.81 × 10^?2, 3.50 × 10^?3 and 3.56 × 10^?4 cm/s, respectively. The results of SWCC tests show that the SWCC curve was steep when matric suction was low, and the shallower the waste the steeper would be the curve. In addition to the field and laboratory tests, an unsaturated–saturated seepage analysis was conducted to simulate the development of the high leachate mound and to calculate the annual leachate production. The simulated volumetric water content in the unsaturated zone was about 40 %, which agreed well with the test result. The calculated leachate mound was consistent with the field measurement. The calculated annual and daily leachate productions were all more reasonable than the results of the HELP model.