Waste/Lining System Interaction: Implications for Landfill Design and Performance
N. Dixon, K. Zamara, D.R.V. Jones, G. Fowmes
ABSTRACT: Despite the relative maturity of landfill design practice, world-wide there are still significant numbers of large scale failures of waste bodies, often incorporating the lining system. In addition, there is growing evidence that post waste placement deformations in the lining system are leading to loss of function (i.e. discontinuous drainage layers, loss on protection and leaking liners). Best practice has established that both stability and integrity of the lining system must be assessed during the design process, and specifically that interaction between the waste body and lining system should be considered both in the short-term (i.e. during construction) and long-term (i.e. following waste degradation). The paper introduces available analysis approaches, reviews knowledge of waste behaviour required for such analyses and provides guidance on the mechanisms to consider. The need for field monitoring to validate numerical models is established as is the need for extensive measurements of waste mechanics properties linked to a standard classification system to aid comparison and use. The benefits of using probability of failure analysis to incorporate material and test variability in design are highlighted.
Wrinkling of a Geomembrane on a Compacted Clay Liner on a Slope
R. K. Rowe, P. Yang, M.J. Chappel, R.W.I. Brachman , W.A. Take
ABSTRACT: The development of wrinkles in a 1.5 mm thick textured HDPE geomembraneover a compacted clay liner on a 3H:1V (33%; 18°) slope is reported at different times of the day on 25 August 2008. The width of wrinkles did not vary significantly throughout the day once notable wrinkling had developed. The mean wrinkle width (0.31 m) is greater than that at other sites with a GCL below the geomembranereported in the literature (0.21-0.23m). The maximum connected wrinkle ranged from less than 20 m at 08:40 to 1370 m at 15:10. Given the size of the area monitored(0.26 ha) one might expect about four such wrinkles per hectare. Wrinkles covered less than 2% of the area at 08:40 but exceeded 8% after 10:10 with a maximum of 20% at 15:10. The practical implications of the time of day the geomembrane is covered and the effect this could have on leakage are discussed.
KEYWORDS: geomembranes, wrinkles, landfills, liners, leakage
Diffusion of phenolic compounds through an HDPE geomembrane
N. Touze-Foltz, M. Ahari, M. Mendes, C. Barral, M. Gardoni and L. Mazeas
ABSTRACT: The experimental results obtained regarding diffusion through a high density polyethylene geomembrane of phenol, o-cresol, p-cresol, 2,4-xylenol, 3,4-xylenol, 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,5,6-tetrachlorophenol, pentachlorophenol and bisphenol A are presented. Partitioning coefficients range from 0.3 to 205 respectively for phenol and pentachlorophenol. Diffusion coefficients lie in the range 1.1×10 -13 to 4.3×10 -13 m 2 /s respectively for 2-methylphenol and bisphenol A. The effect of aqueous solubility, n-octanol/water partitioning coefficient, molecular diameter and molecular weight on partitioning coefficient, diffusion coefficient and permeation coefficient were studied. Different trends from the ones previously given in the literature for volatile organic compounds (VOCs) were observed. An increase in the number of chlorine atom on the phenolic nucleus results in an increase of the partitioning coefficient and permeation coefficient, probably linked to the polarity of the molecules under study.
Shear-Induced Geomembrane Damage due to Gravel in Underlying Compacted Clay
P. J. Fox, C. Athanassopoulos, S. S. Thielmann, and A. N. Stern
ABSTRACT: Lining systems for landfills and heap leach pads are often constructed with compacted clay liners (CCLs) containing significant amounts of gravel. Geomembranes placed against gravelly CCLs are vulnerable to damage due tohighoverburden stress andinterface shear displacement. This invited paper reports results from the first experimental investigation of shear-induced damage to geomembranes placed in contact with gravelly compacted clay. A series of large-scale direct shear tests was conducted for the interface between smoothHDPE geomembranes and CCLs with 20 percent gravel. The tests were performed for normal stress levels ranging from 72 to 1658 kPa to simulate overburden stresses associated with bottom liner systems. Replicate interface shear tests were also performed for normal stresses up to 4145 kPa with a geosynthetic clay liner (GCL) placed in between the geomembrane and the CCL to evaluate protection provided by the GCL. Results indicate that shear displacement between a geomembrane and a gravelly CCL under high normal stress conditions can cause severe damage to the geomembrane. The testing program also found that placing a GCL between a geomembrane and a gravellyCCL can essentially eliminate such damage.
Evaluation of mineral barriers against acid rock drainage
A. Naka, T. Katsumi, G. Flores, T. Inui, T. Ohta, T. Urakoshi, and T. Ishihara
ABSTRACT: The barrier performance of geosynthetic clay liners (GCLs) containing Na-bentonite, zeolite, and ferrihydrate against acid rock drainage (ARD) was evaluated through hydraulic conductivity and sorption tests in order to determine their applicability as adsorption layers in waste rock containment facilities. The hydraulic conductivity (k) of GCL permeated with water was 1.4×10-11 m/s and this increased by one order of magnitude with ARDpermeation (k= 5.0×10-10 m/s). The k of zeolite permeated with water was 3.0×10-10 m/s and this also increased with ARDpermeation (k = 1.4×10-9 m/s). The k value of ferrihydrate was 7.3×10-9 m/s when permeated with water and this remained constant after ARD permeation (k= 8.6×10-9 m/s). Metal sorption of bentonite, zeolite, and ferrihydrate were different in terms of sorption capacity and selectivity, which can be summarized as follows: bentonite: Cu>Fe>Zn>Al>As>Pb, zeolite: Cu>Fe>Zn>Pb Al As, and ferrihydrate: Cu>Zn>Al>As>Pb. According to experimental results, the tree minerals appear to be good candidates for ARD mitigation.
Improvement on the Performance of Geosynthetic Clay Liners Using Polymer Modified Bentonite
Y. Liu, W. P. Gates and A. Bouazza
ABSTRACT: Polymers have been added to improve bentonite swelling capacity with the view of improving the hydraulic performance of GCLs. This paper presents an on-going study in which three bentonites were polymer-treated (0.5%, 1%, 2% by weight) and polymerincluded changes to swell index and Atterberg limits were determined. The liquid limit values generally increased with polymer content, although a decrease appeared at higher concentration of some polymers. However, polymer addition had only slight effects on plastic limits. Higher polymer concentration, regardless of type, generally resulted in higher swell index values and swell percentages. Different response of bentonites to polymers occurred which is mainly due to the individual characteristics of bentonites, such as chemical composition, type of gel formation etc.
Effect of Settlement rate and Geogrid reinforcement on the Deformation Behaviour of Soil barriers of Landfill Covers: Centrifuge Study
S. Rajesh and B.V.S. Viswanadham
ABSTRACT: The objective of this paper is to examine the influence of settlement rate and geogrid reinforcement on the deformation behaviour of soil barriers of landfill covers subjected to differential settlements. A series of centrifuge tests were performed on soil barriers at 40 gravities. Two different settlement rates were induced using motor-based differential settlement simulator designed for a high gravity environment. Centrifuge tests on a 1.2 m thick unreinforced soil barrier subjected to two different settlement rates without provision of any overburden pressure was found to experience identical deformation profiles and cracking pattern. A slight delay in the occurrence of crack initiation and an increase in the strain at crack initiation was noticed when the soil barrier was tested at slow settlement rate. An increase in the limiting distortion level from 0.044 to 0.069 was noticed when the unreinforced soil barrier was subjected to an overburden pressure equivalent to that of cover system. When the soil barrier was reinforced with a geogrid layer without any overburden pressure, the limiting distortion level was increased from 0.044 to 0.064. An increase in the maximum mobilized tensile load of model geogrid from 77 kN/m to 120 kN/m was observed with the provision of overburden pressureequivalent to that of cover system.
Effect of differential settlements on the sealing efficiency of GCLs compared to CCLs: Centrifuge Study
B.V.S. Viswanadham, S. Rajesh and A. Bouazza
ABSTRACT: Geosynthetic clay liners (GCLs) are being used as an alternative to compacted clays in landfill cover systems because of their very low hydraulic conductivity to water and ease of placement. The main objective of this paper is to examine the performance of GCLs subjected to continuous differential settlements during a centrifuge test at 40 gravities. This paper presents results to two centrifuge model tests, one on clay-based cover system and another on GCL-based cover system. Both models were subjected to an overburden equivalent to that of landfill covers and are instrumented to measure sealing efficiency at the onset of differential settlements. Limiting maximum distortion level at which the barrier system loses it sealing efficiency could be established. For the type of cover systems investigated, the ability of GCL-based cover system to withstand differential settlements without losing their sealing efficiency was found to be superior to that of clay based cover system.
Geosynthetic Lining System for Modern Waste Facilities – Experiences in Developing Asia
H. B. Ng and B. Ramsey
ABSTRACT: The applications of geosynthetic liner systems are being used with increasing frequency, particularly for the environmental engineering applications in developing countries at recent years. Polyethylene geomembrane sheets have been widely accepted as a standard component of geosynthetic lining system in the waste containments for decades, which includes solid waste sanitary landfill and wastewater treatment lagoons. The paper presents the application of impervious Polyethylene geomembrane used as bottom liners and final capping systems in waste containment facilities in developing Asia. This paper discusses the characteristics and durability of polyethylene geomembrane as a lining solution to the waste containments. Successful case histories on the application of polyethylene geomembranes in bottom liner and final capping systems of modern solid waste facilities are illustrated.
