Effect of geotextile ageing and geomembrane surface roughness on the geomembrane-geotextile interfaces for heap leaching applications

doi:10.1016/j.geotexmem.2021.09.001

Geotextiles and Geomembranes

Volume 50, Issue 1, February 2022, Pages 55-68

https://doi.org/10.1016/j.geotexmem.2021.09.001 Get rights and content

Highlights

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Under normal stresses up to 1000 kPa, no surface damage was observed in any of the geomembranes surface roughness.
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Decreasing the geotextile mass per unit area, increased the friction angles for the geomembrane-geotextile interface.
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Ageing of single-layer geotextiles resulted in an increase in peak interface friction angle.
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Geotextile ageing resulted in higher post peak strength.
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Preaged heat bonded two-layer geotextile exhibited internal failure at the interface between the two layers of the geotextile.

Abstract

A series of large scale direct shear experiments is used to investigate the effect of the geomembrane (GMB) surface roughness, geotextile (GTX) properties, and GTX ageing, on the GMB-GTX interface shear behaviour. Interfaces involving smooth, coextruded textured, and structured surface GMBs underlying four different nonwoven needle-punched staple fibres (GTXs) with mass per unit areas between 200 and 2400 g/m², and a geocomposite drain (GCD) are examined at normal stresses between 250 and 1000 kPa. The results showed that the interlocking between the GMB and GTX increased with increasing the GMB asperity height and/or decreasing the mass per unit area of the GTX. For the interfaces that involved GTXs preaged prior to the shear box experiments for up to 2 years at 85 °C, it was found that the 2400 g/m² heat bonded two-layered GTX exhibited internal shear failure at low shear displacements. However, all the highly aged single layered GTXs showed an increase in the peak interface friction angles with the increase in their ageing. For these single layered GTX, the results suggest that assessing the interface friction angles using unaged GTXs for the stability analysis is conservative as long as the GTX remains intact in the field.

Introduction

Barrier systems for waste containment or mineral resource extraction applications are typically constructed on different layers of geosynthetics and soils to minimize the leakage of fluids containing the contaminants to the surrounding environment. These facilities can be constructed on sloping grounds or with steep side slopes to maximize capacity or to reduce the footprint of the waste containment or the mining operation. In this case, the shear resistances of the interfaces between the different components of the geosynthetic barrier system become an important consideration for the global stability of the facility.

Inadequate interface shear resistance of the liner materials or inaccurate assessment of their interface shear properties have led to sliding failures and global instability of the slopes in many previous case histories (e.g., Von Pein and Lewis 1991; Byrne et al., 1992; Breitenbach 1997; Stark 2013). For municipal solid waste (MSW) landfill applications, many previous studies (e.g., Stark et al., 1996; Jones and Dixon 1998; Li and Gilbert 1999; Seeger et al., 1999; Wasti and Ozduzgun 2001; Bacas et al., 2015; Stark et al., 2015; Cen et al., 2018) have investigated the interface shear behaviour of different geosynthetic-geosynthetic and geosynthetic-soil interfaces that have allowed better understanding of the shear behaviour of the interfaces. This has led to better stability of the geosynthetic materials on the slopes of these facilities and hence, avoiding major remediation costs resulting from inadequate designs. However, there is a paucity of research investigating the interface shear of the geosynthetic liner system components for mining applications that involve very different service conditions from that in MSW landfills where most of the research has previously been directed (Breitenbach and Thiel 2005).

Section snippets

Background

Among the different mining applications that involve the use of geosynthetics, heap leaching is considered one of the most aggressive service environments for the liner system (Scheirs 2009). In this process, the mined ore is usually crushed and heaped on a lined pad and then irrigated with either basic or acidic solutions to dissolve and extract the valuable metals (Christie and Smith 2013; Smith 2014). With ore heights reaching 100 m and in some cases approaching 240 m, the overburden

Geomembranes

Four different high density polyethylene (HDPE) GMBs with the same hardness (ASTM D2240) but with different surface roughnesses (Table 1) were examined in this study. Smooth-GMB and Textured-GMB were produced by Manufacturer 1 using a blown film process with a nominal thickness of 2.0 mm. Smooth-GMB had smooth black surfaces, whereas Textured-GMB was coextruded with a white upper layer and textured on both sides by injecting inert gas into the two skin layers during extrusion to give an average

Results and discussion

All the examined interfaces showed essentially frictional behaviour that was modelled using Mohr- Coulomb shear strength envelope to assess the interface shear strength parameters (the interface friction angle " $δ "$ and adhesion “c_a”). The friction angle obtained from the envelopes corresponding to the maximum shear stress at a given normal stress range was referred to as the peak friction angle ( $δ$ p), whereas the angle obtained from the shear stresses corresponding to 45 mm of shear displacement

Conclusion

The effects of the GTX ageing, GTX properties, and the GMB surface roughness techniques on the interface shear behaviour of the GMB-GTX interface were examined using direct shear box tests at 250, 700, 1000 kPa normal stress. Four different HDPE GMBs with different surface roughnesses, including a Smooth-GMB, coextruded Textured-GMB, and two structured surface GMBs (Spike-GMB and Stud-GMB) were examined with four different GTXs with μ_a of 200, 580, 1500, and 2400 g/m² (GTX1, GTX2, GTX3, and

Acknowledgement

The research presented in this paper was funded by the Natural Science and Engineering Research Council of Canada (NSERC) to F. B. Abdelaal (RGPIN-2018-04091), and used equipment provided by funding from the Canada Foundation for Innovation (CFI) and the Ontario Ministry of Research and Innovation.

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The interface shear strength involving geosynthetics and other materials can be influenced by various parameters, such as the material type and the normal stress on the interface. Although several investigations have been conducted over the years on this topic, the large variation of interfaces that can be used has led researchers to develop other sources of information to improve design methods. This paper investigates how roughness parameters can influence the shear strength developed between different interfaces based on many inclined plane tests and microscopic analyses of the surface roughness. One smooth and three textured geomembranes were used to simulate a barrier layer and sand, and two nonwoven geotextiles were installed on them to simulate drainage or protective layers. A powerful optical apparatus provided fifteen bidimensional and tridimensional surface parameters for the two faces of the analyzed geomembranes. The results showed that the mean height of profile elements (R_c) and the core material volume (V_mc) parameters presented stronger correlations with the interface shear strength. The concept of interface roughness factor was introduced to estimate the interface friction between different materials based on the materials properties for interfaces with geotextiles.

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Effect of geotextile ageing and geomembrane surface roughness on the geomembrane-geotextile interfaces for heap leaching applications

Highlights

Abstract

Introduction

Section snippets

Background

Geomembranes

Results and discussion

Conclusion

Acknowledgement

Geotext. Geomembranes

Polym. Test.

Journal of Rock Mechanics and Geotechnical Engineering

Geotext. Geomembranes

Construct. Build. Mater.

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Cold Reg. Sci. Technol.

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Geotext. Geomembranes

Degradation of a HDPE geomembrane without HALS in chlorinated water

Geosynth. Int.

Effect of high pH found in low-level radioactive waste leachates on the antioxidant depletion of a HDPE geomembrane

Journal of Hazardous, Toxic, and Radioactive Waste,ASCE

Durability of three HDPE geomembranes immersed in different fluids at 85°C

Journal of Geotechnical and Geoenvironmental Engineering,ASCE

Brittle rupture of an aged HPDE geomembrane at local gravel indentations under simulated field conditions

Geosynth. Int.

OIT depletion in HDPE geomembranes used in contact with solutions having very high and low pH

Shear strength of the geomembrane–subgrade interface in heap leaching applications

Environ. Geotech.

The influence of asperities and surface roughness on geomembrane/geotextile interface friction angle

International Journal of Geosynthetics and Ground Engineering

Interface shear-strength properties of textured polyethylene geomembranes

Short-term local tensile strains in HDPE heap leach geomembranes from coarse overliner materials

Journal of Geotechnical and Geoenvironmental Engineering, ASCE