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1.
Preventing the penetration of rainwater into a landfill site is the main purpose of the final cover in landfill sites. Conventional designs of landfill covers use geotextiles, such as geomembrane and geosynthetic clay liners, and clay liners to lower the permeability of the final cover of landfill sites. However, differential settlement and climatic effects in landfill sites instigate crack development or structural damage inside the final cover. This study therefore investigates the field applicability of a self-recovering sustainable liner (SRSL) as an alternative to the landfill final cover. The SRSL utilizes the precipitation reaction of two chemical materials to form precipitates that fill the pores and thereby lower the overall permeability of the liner. To examine the field applicability of the SRSL system, uniaxial compression tests and laboratory hydraulic conductivity tests were performed under various climatic effects such as wet/dry and freeze/thaw processes. Furthermore, field-scale hydraulic conductivity tests were performed with intentionally induced cracks to demonstrate the self-recovery performance for practical applications. Extensive laboratory and field test results confirmed the capability of the SRSL final cover system to fulfill the strength and hydraulic conductivity requirements, even in harsh field conditions. 相似文献
2.
Performance-based design of landfill liners 总被引：6，自引：0，他引：6
Factors affecting chemical transport in geomembrane, clay and composite liners are reviewed, and a simplified performance-based method for evaluating landfill bottom liners is presented. For single geomembrane liners, mass transport of inorganic chemicals is calculated from the leakage rate from holes for an assumed frequency of hole occurrence. Transport of organic chemicals is obtained by accounting for molecular diffusion through the intact geomembrane. Migration of inorganic and organic chemicals in compacted clay liners is calculated using a solution of the 1D advection–dispersion-reaction equation. For composite liners consisting of a geomembrane and a clay liner, 3D flow and transport of inorganic chemicals is approximated using an equivalent 1D model for transport through an effective area of transport. The approximation is based on results from 3D analyses that have been conducted for a variety of cases. Migration of organic chemicals through composite liners is calculated using a 1D diffusion model. Applicability of the method is illustrated by using it to evaluate the relative performance of several different liner systems. 相似文献
3.
Clay liners or compacted earthen barriers are important barrier materials used for preventing contaminant transport through soils. A low hydraulic conductivity (k) is a significant parameter that governs the design and construction of clay liners. Compacted expansive clays, which are montmorillonite clays, also have a very low hydraulic conductivity (k). When expansive clays are blended with fly ash, an industrial waste, the hydraulic conductivity (k) further reduces as the ash-clay blends result in increased dry densities at increased fly ash contents. Hence, fly ash-stabilised expansive clay can also be proposed as a unique clay liner material. As expansive clays undergo heave when they come into contact with water, it is necessary to study the heave behaviour of fly ash-stabilised expansive clay liners. This paper presents heave studies on fly ash-stabilised expansive clay liners. Fly ash in different contents by dry weight of the expansive clay was added to the clay, and the ash-clay blend was compacted as a liner overlying a natural field soil layer. Compacted lateritic clay was used for simulating the natural field soil into which contaminants migrate. Calcium chloride (CaCl2) solution of varying concentration (5, 10, 20, 50, 100 and 500 mM) was used as the permeating fluid in the heave studies. The rate of heave and the amount of heave of the fly ash-stabilised expansive clay liners were monitored. Deionised water (DIW) was also used as inundating fluid for comparative study. Heave (mm) decreased with increase in solute concentration for all fly ash contents. For a given solute concentration, heave decreased up to a fly ash content of 20 % and thereafter it increased when the fly ash content was increased to 30 %. Heave of the fly ash-stabilised expansive clay liners was correlated with their permeability, liquid limit (LL) and free swell index (FSI) pertaining to the respective fly ash content and CaCl2 concentration. 相似文献
4.
Frost heave thrust of soil varies with its water content. When the water content of the soil is less than its plastic limit, the horizontal frost heave thrust of soil does not appear. When the water content of the soil is greater than its plastic limit the frost heave thrust increases with increasing water content and when the water content is a little over its liquid limit, it reaches a maximum value.
Also, the horizontal frost heave thrust of soil varies with temperature. It increases as the negative temperature falls, until it reaches a maximum value at about −7°C.
It should be noted that the distribution of the horizontal frost heave thrust along the lateral surface of the structure is not always uniform: its value is greatest at the middle, less at the bottom, and least at the top. The maximum value generally appears at the place where the depth is about 60–80% of the depth of frost penetration.
According to laboratory data and engineering practice, the values of horizontal frost heave thrust vary greatly, but its maximum value is generally about 4.1–4.2 kg/cm2. 相似文献
5.
Engineering geological aspects of replacing a solid waste disposal site with a sanitary landfill 总被引：1，自引：0，他引：1
Kamil Kayabali 《Engineering Geology》1996,44(1-4):203-212
The current solid waste disposal site in the Mamak district of Ankara is being engulfed by the growing city. All varieties of solid wastes, including medical wastes, are stored at the present site in an irregular manner. Topographical and geological conditions at Mamak waste site are favorable for constructing a sanitary landfill. Located at the edge of a topographical depression, the site is underlain by the natural hydraulic barriers such as clay and metagreywacke. The terrestrial clay has a permeability of 10−7 to 10−8 cm/s and low to moderate values of CEC. The proposed sanitary landfill to replace the present solid waste site has a capacity of storing solid waste over 50 years. The details of base liner, final cover, toe embankment, and drainage of leachate and gas are presented in the paper. 相似文献
6.
Abbas El‐Zein 《国际地质力学数值与分析法杂志》2008,32(3):265-287
Finite‐element models of contaminant transport through composite landfill liners require highly refined meshes around the interface between the geomembrane and the clay layer, especially if leakage through holes in the geomembrane is considered. In addition, no general formulation for transport through leaking geomembranes can be found in the literature. The paper develops a general approach to time‐dependent contaminant migration through composite liners with intact or leaking geomembranes. Equations are derived for various combinations of system conditions including Dirichlet and Neumann boundary conditions in the waste, constant mass of contaminants in the waste, steady state or transient transport in the geomembrane, and steady state or transient seepage velocities in the mineral liner. The effect of the geomembrane on transport in the soil is converted into an equivalent boundary condition applicable at the top of the clay layer. Hence, only the media underlying the top geomembrane are explicitly represented in the numerical model, yielding a computationally efficient algorithm. The new formulation is validated in conjunction with finite‐layer, finite‐element and boundary‐element methods, by comparing its predictions to those of more conventional approaches which represent the geomembrane explicitly. The scope of the method is illustrated by modelling a landfill liner with a geomembrane leaking in five locations. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
7.
建立系列模拟实验研究了冻融作用对垃圾填埋场防渗层防渗和去污性能的影响。实验结果表明：冻融作用对垃圾填埋场防渗层有一定的破坏作用,对渗透系数和污染物的去除能力均有重要影响;冻融前的渗透系数均低于国家标准（1.0×10-7 cm/s）,冻融后防渗层的渗透系数增加2～6倍;防渗层对COD、Cl-和NH+4的去除率分别从冻融前的68.6%、31.6％和70.5％变为86.2%、18.2％和23.0％。 相似文献
8.
An analytical solution for one-dimensional contaminant diffusion through multi-layered media is derived regarding the change
of the concentration of contaminants at the top boundary with time. The model accounts for the arbitrary initial conditions
and the conditions of zero concentration and zero mass flux on the bottom boundary. The average degree of diffusion of the
layered system is introduced on the basis of the solution. The results obtained by the presented analytical solutions agree
well with those obtained by the numerical methods presented in the literature papers. The application of the analytical solution
to the problem of landfill liner design is illustrated by considering a composite liner consisting of geomembrane and compacted
clay liner. The results show that the 100-year mass flux of benzene at the bottom of the composite liner is 45 times higher
than that of acetone for the same composite liner. The half-life of the contaminant has a great influence on the solute flux
of benzene diffused into the underlying aquifer. Results also indicates that an additional 2.9–5.0 m of the conventional (untreated)
compacted clay liner under the geomembrane is required to achieve the same level of protection as provided by 0.60 m of the
Hexadecyltrimethylammonium (HDTMA)-treated compacted clay liners in conjunction with the geomembrane. Applications of the
solution are also presented in the context of a contaminated two-layered media to demonstrate that different boundary and
initial conditions can greatly affect the decontamination rate of the problem. The method is relatively simple to apply and
can be used for performing equivalency analysis of landfill liners, preliminary design of groundwater remediation system,
evaluating experimental results, and verifying more complex numerical models. 相似文献
9.
首先对斑脱土衬里(粘土-斑脱土、砂-斑脱土) 进行变水头实验, 得粘土-斑脱土的渗透系数为6.0×10-9~3.0×10-8cm/s, 砂-斑脱土的渗透系数为1.0×10-9~3.0×10-9cm/s.从防渗角度分析, 2种斑脱土混合物均适合作垃圾填埋场的底层衬里.然后对斑脱土衬里进行持水与水迁移实验, 评价斑脱土衬里水的迁移特性.以水迁移实验为基础, 模拟斑脱土衬里与地基5种不同含水量的条件, 对斑脱土衬里进行直接剪切实验, 测定斑脱土衬里的剪切强度及斑脱土衬里与地基接触面的剪切强度.再对斑脱土衬里进行三轴固结不排水实验, 测定其总剪切强度与有效剪切强度.实验结果表明: 地下水具有很大的潜力从地基流向斑脱土衬里, 从而大大提高斑脱土衬里的含水量; 随着含水量的增加, 粘土-斑脱土、砂-斑脱土衬里的抗剪强度逐渐减小.根据实验所获得的抗剪强度参数, 选择日本山谷型垃圾填埋场典型剖面, 对山谷型垃圾填埋场进行稳定性评价.结果表明: 对于角度小于20°的缓倾角山谷型垃圾填埋场, 使用粘土-斑脱土、砂-斑脱土作为底层衬里是稳定的.因此, 2种斑脱土混合物适合作山谷型垃圾填埋场的底层衬里. 相似文献
10.
中国冻胀研究进展 总被引：14，自引：0，他引：14
中国的冻胀研究从５０年代末期开始，经科研单位、勘察设计院和大专院校冻土工作者近４０年的努力，通过现场观察、原位测试、室内试验和计算机模拟等多种手段，开展了冻胀量、冻胀力、冻胀机理、冻胀预报和各类工程防冻胀措施研究，取得了丰硕成果。提出了冻土工程分类、冻胀量和冻胀力的设计值和估算方法，以及各类工程防冻胀破坏的行之有效的方法。目前，研究工作正朝着从表象到机理、从宏观到微观的方向深化。进一步研究多孔介质中热质迁移的物理过程，特别是水分迁移的驱动力与温度或温度梯度间的相互关系，提出能反映过程物理本质且简便的冻胀预报模式及研制出对冻胀不敏感的新材料应成为今后工作的重点。 相似文献
11.
Yahia E.-A. Mohamedzein Amer A. Al-Rawas Mohammed Y. Al-Aghbari Ahmed Qatan Abdul-Hamid Al-Rawas 《Engineering Geology》2005,80(3-4):271-281
The possibility of using crushed shales as landfill liners is investigated in this study. Two types of shales were studied by performing the following laboratory tests: hydraulic conductivity, compaction, swelling, consolidation, X-ray diffraction (XRD), scanning electron microscope (SEM) and chemical analysis. For both compacted shales, the hydraulic conductivity was in order of 10− 7 cm/s or less which satisfies the specifications for landfill liners. The results of XRD and SEM support the low values of the hydraulic conductivity. Because of the dominant presence of low-activity kaolinite, there was no significant change in the hydraulic conductivity when the compacted shales are exposed to calcium chloride solution. The compressibility of the compacted clay was low and no serious post-construction settlement is expected. The shear strength of the compacted shales was within the usual expected range for earthen liners and, therefore, should pose no challenges with respect to shear strength. The crushed shales also satisfy the other criteria related to Atterberg limits and grain size. 相似文献
12.
吉林省季节冻土冻结深度变化及对气候的响应 总被引：2，自引：2，他引：0
为了掌握季节冻土冻结深度的变化对气候的响应,利用1961-2015年吉林省46个气象站的逐日平均气温、地表温度、积雪深度、冻土冻结深度等数据,采用线性倾向估计、突变分析等方法,研究了吉林省季节冻土冻结深度的时空演变规律及其与气温、积雪的关系。结果表明：吉林省季节冻土最大冻结深度呈由西向东逐渐减小的空间分布特征,绝大多数站最大冻结深度呈减小趋势。基本上在10月开始冻结,次年3月达到最深,6月完全融化。西部冻土冻结深度变幅较大,其次是中部,东部最小。1961-2015年季节冻土最大冻结深度以-5.8 cm·（10a）-1的速率显著减小（P<0.01）。最大冻结深度基本上呈逐年代减小的趋势,从20世纪90年代开始,最大冻结深度明显减小。最大冻结深度在1987年发生了突变,突变后平均最大冻结深度比突变前平均最大冻结深度减小了22.2 cm。通过分析气温和积雪深度对冻结深度的影响,认为冻土冻结深度对气温变化较为敏感,绝大多数站最大冻结深度与平均气温呈负相关关系。在年际变化上,气温的上升是最大冻结深度减小的主要原因。在季节冻土稳定冻结期,积雪深度超过10 cm,保温作用逐渐变强;当积雪深度达到20 cm时,保温作用显著,冻土冻结深度变浅。 相似文献
13.
钻孔埋管注盐法整治季节冻土区路基冻害现场试验研究 总被引：1，自引：0，他引：1
以季节冻土区青藏铁路环青海湖段路基冻害为背景,通过选取典型冻害断面,从水分、温度和土性三个方面分析了环湖段路基冻害成因。根据路基病害处理中成熟应用的注浆和注盐法,提出采用钻孔埋管注盐法整治路基病害技术,通过现场冻胀观测,检验注盐法整治路基的有效性。结果表明：环湖段路基冻害主要是由于路基土体内存在一层低液限低渗透性的粉质黏土,黏粒含量高,含水率大,冻深最大为1.5 m,粉质黏土层冻结,引起路基冻胀。结合现场试验段,对用盐量、盐的成分、施工工艺与参数提出合理的施工建议。现场冻胀监测表明,钻孔埋管注盐段路基的冻胀量明显降低,可用于季节冻土区路基冻害的整治治理。 相似文献
14.
In this paper, a thermo-mechanical model is proposed to simulate the frost jacking behaviour of screw piles subjected to frost heave, and the results are further validated by laboratory tests. The calculated results show that large multi-helix piles yield the least frost jacking when the freezing depth reaches half the embedment depth of pile. Based on the modified cylindrical shear method and individual bearing method, the optimal geometric parameters of screw piles are determined by a series of numerical calculations. The numerical approach is expected to serve as a reference for designing effective and economical pile types in practice. 相似文献
15.
Over the last decade, waste disposal has become a particularly sensitive issue in Algeria. New legislation concerning landfill
liner design has been adopted. Traditional methods of landfill liner characterization involve soil sampling and chemical analysis,
which are costly, destructive and time-consuming. New techniques are currently being investigated that aim to provide nondestructive
liner characterisation. This paper details technical aspects associated with electrical conductivity measurements within landfill
liners and presents experimental work to show the direct application of electrical techniques to track ionic movement through
a sand bentonite liner under chemically induced flow. Samples of sand bentonite were mixed and compacted with NaCl electrolytes
at different concentrations. The electrical conductivities of compacted specimens were measured with a two-electrode cell.
The effects of frequency and electrolyte concentration on the conductivity measurement were explored. The relationship between
the soil electrical conductivity and the NaCl electrolyte concentration in interstitial pore fluid was determined. The conductivity
measurements were used to quantify the pore fluid concentration and effective diffusion coefficient of sand bentonite liners.
It is concluded here that the electrical conductivity of compacted specimens depends mainly on the salt concentration in the
pore fluid, and that this approach could therefore be used to track ionic movement through liners during diffusion. 相似文献
16.
通过对季节性冻土区铁路路基冻胀量与地层温度的监测,可以了解监测段的冻胀变化过程,但无法对未来的发展趋势作出有效预测。本文采用GM（1,1）模型对监测段落路基的冻胀变形及冻结深度的变化情况进行预测。结果表明,此预测方法可以在现有监测数据的基础上有效预测短期内路基冻胀的发展趋势。根据模型预测结果,可以提前采取有效整治措施,便于决策者对轨道检验周期、维修周期、限速周期等作出合理调整。 相似文献
17.
垃圾填埋场传统封顶和ET封顶的比较研究 总被引：3，自引：0，他引：3
针对传统压实黏土封顶系统存在易干燥开裂的问题,提出了一种新型的ET（蒸发传输）封顶系统。分析了压实黏土封顶系统和新型ET封顶系统的工作机制。在降水和蒸发循环补给的条件下,建立了水分在两种封顶系统中迁移的一维数学模型。以9次降水和蒸发循环补给为边界条件,分别模拟了576 h的水分在两种封顶系统中迁移变化规律。计算结果表明,距补给边界越近,含水率受降水、蒸发的影响越显著,且随着深度的增加出现明显的峰值滞后现象。传统封顶中的压实黏土层由于具有低渗透性,致使整层不能得到有效的水分补给。ET封顶中整个土层可以有效地从边界降水中得到补给,同时在蒸发的条件下,把土层中的储水释放。数值计算结果与试验数据的对比表明,计算值和试验数据基本吻合。这些研究成果有助于垃圾填埋场封顶系统的设计作进一步的改进。 相似文献
18.
Amer A. Al-Rawas Yahia E-A. Mohamedzein Abdulaziz S. Al-Shabibi Salem Al-Katheiri 《Geotechnical and Geological Engineering》2006,24(5):1365-1383
Absrtract This paper investigates the potential use of sand–attapulgite (palygorskite) mixtures as a landfill liner. The sand and attapulgite
clay used in this study were brought from Wahiba (eastern Oman) and Al-Shuwamiyah (southern Oman), respectively. Initially
the basic properties of the sand and clay were determined. Then the attapulgite clay was added to the sand at 5, 10, 20 and
30% by dry weight of the sand. The sand–attapulgite clay mixtures were subjected to mineralogical, chemical, microfabric and
geotechnical analyses. The X-ray diffraction (XRD) qualitative analysis showed that attapulgite is the major clay mineral.
The chemical compounds, exchangeable cations and cation exchange capacity (CEC) for the␣samples were determined. The CEC for
the sand–clay mixtures is low but increases with the increase in clay content. The scanning electron microscope (SEM) examination
showed that the addition of clay developed coating between and around the sand grains which results in filling the voids and
reducing the hydraulic conductivity of the sand–clay mixtures. The hydraulic conductivity values for the pure clay and sand
+ 30% clay mixture prepared at 2% above optimum water content are slightly higher than hydraulic conductivity requirements
for landfill liners but can be acceptable. The geotechnical study which included grain size distribution, Atterberg limits,
specific gravity, compaction, hydraulic conductivity and shear strength tests showed that the sand+30% clay mixture prepared
at 2% above optimum water content can be considered to satisfy the requirements for landfill liners. For all sand–clay mixtures
no swelling was recorded and the addition of clay to the sand improved the shear strength. 相似文献
19.
Cover systems are widely used to safeguard landfills and contaminated sites. The evaluation of the water balance is crucial
for the design of landfill covers. The Hydrologic Evaluation of Landfill Performance (HELP) model of the US Environmental
Protection Agency was developed for this purpose. This paper discusses some limitations of version 2 of this model and some
operational difficulties for the use of this model in Germany, which has been developed for the United States. The model results
are tested against field data of the water balance, measured on test fields on the Georgswerder landfill in Hamburg. Theoretically,
HELP considers gravitational forces as driving forces of water flow only. Therefore capillary barriers cannot be simulated.
Furthermore, the formation of and the flow through macropores are not considered, a main critical process that the diminishes
the effectiveness of compacted soil liners. In the output comparison, the matching of measured and simulated data is quite
good for lateral drainage, but failed for surface runoff and liner leakage through compacted soil liners. A further validation
study is planned for HELP version 3 using a broader range of test field data.
Received: 10 January 1995 · Accepted: 14 November 1995 相似文献
20.
Composite landfill liner design with Ankara clay, Turkey 总被引：1，自引：0，他引：1
This study presents an overview of the geotechnical properties of the clayey soils, referred to as Ankara clay, at two sites of the Ankara region in an attempt to design a landfill profile composed of a high density polyethylene (HDPE) geomembrane/clay composite liner through the Hydrologic Evaluation of Landfill Performance (HELP) model and the Water Balance Method. The geotechnical properties of the landfill layers along with the water balance factors (i.e., evapotranspiration, precipitation, temperature, etc.) were assessed to determine the height of the water-saturated zone in the refuse above the composite liner for landfill design. The cumulative expected leakage rates through the composite liner constructed with compacted Ankara clay were related quantitatively to the cumulative average leachate head. The results of this investigation show that the leakage rates through the composite liner are within tolerable limits. 相似文献