White Papers

A Test Method to Determine Expected GCL Porosity under Specific Site Conditions

D.T. Gibbs, W. P. Gates

ABSTRACT

Determination of the porosity and void ratio of porous shrink-swell materials under conditions experienced on-site is critical to understanding expected advective and/or diffusive flux. Porosity estimates for geosynthetic clay liners (GCLs) depend on subtle interactions within the pore spaces governed by a particular leachate flux processes. For clay based lining materials, such as geosynthetic clay liners or compacted clay, the effective porosity or void ratio depends on the effective stress, saturation conditions of the lining system and the interactions between the leachate and the clay, which impact flow path tortuosity. This paper will describe a test method to calculate the porosity of GCLs under specific conditions of effective stress and saturation...

Durability of Polyester Geotextiles Subjected to Australian Outdoor and Accelerated Weathering

D.T. Gibbs, R. A. Austin, D. M. Smith

ABSTRACT

Polyester geotextiles are used in a variety of engineering applications, some of which require them to be exposed to sunlight for months or even years at a time eg. protection layers in landfills, filtration layers in tailings dams etc. Photodegradation through exposure to ultraviolet radiation (UVR) is one of the primary degradation mechanisms of synthetic polymeric materials. Polyester (PET) has a higher resistance to photodegradation than unstabilized polyolefin materials such as HDPE and Polypropylene, primarily due to the inclusion of carbon-based benzene rings within the polymer structure....

Forensic Examination of Field GCL Performance in Landfill Capping and Mining Containment Applications

J Buckley, W P Gates, D Gibbs, F Gassner

ABSTRACT

Geosynthetic Clay Liners (GCL’s) have been used in landfill capping and mine containment applications in the Australian environment over the last 14 years. Their use as hydraulic / gas barriers has been accepted by regulatory authorities and design engineers over this time.

The aim of this paper is to evaluate the field performance of GCL’s in terms of hydraulic performance, changes to bentonite mineralogy and physical characteristics. While GCL index properties are appreciated by designers, the performance of GCL’s under Australian environmental conditions requires further research to ensure these characteristics provide the desired environmental safety margin. This paper outlines a study of the in-field performance of GCL’s exhumed from landfill capping and mine containment sites around Australia.

GEOMEMBRANE PROTECTION USING CUSHIONING GEOTEXTILES

R.A Austin, Daniel T Gibbs and P. K. Kendall

ABSTRACT

Geotextiles are widely used to protect geomembranes from installation and in-service damage in applications where eliminating puncturing and the control of membrane strain are critical for the long-term performance of the lining system. In lining applications, protecting the membrane from excessive point loading from the overlying drainage stone and thus minimising potential for environmental stress cracking is desirable, if the long-term performance of the liner is to be assured...

Improvements in Geomembrane Protection Efficiency Using Cushioning Geotextiles

R.A Austin, Daniel T Gibbs and P. K. Kendall

ABSTRACT

The use of geotextiles as protection layers for geomembranes in lining applications is a common use for geotextiles and minimising installation damage, in-service damage and geomembrane strain is critical for the long-term performance of the lining system. In such applications, protection of the membrane from localised point loads caused by the overlying drainage stone thus minimising potential for environmental stress cracking is desirable, if the long-term performance of the liner is to be assured...

Techniques for reducing risk and increasing safety from rockfalls in open mines in Australia

J. Berends, D. Chaychuk and G. Giacchetti

ABSTRACT

As mine operations progress, early mine excavations may receive a reduced technical focus. However, ongoing weathering can increase the risk posed by unstable surfaces within mine operations. This paper presents two examples where earlier mine excavations caused slope instability which had the potential to impact current mining operations. The examples presented illustrate two different solutions to similar problems. This paper explores the projects and explains why different solutions were selected. Boral Quarry in Adelaide featured an unstable 60 year old, excavated face 90m in height. Rock falls from the slope were affecting mining operations below. Due to limited site access coupled with the size and irregular profile of the slope, a high strength flexible barrier system was selected in favour of the more traditional mesh based remediation...

RESEARCH AND ANALYSIS OF GEOSYNTHETICS FOR A TAILINGS STORAGE APPLICATION

M. Amtsberg, J. Buckley and C. Lane

ABSTRACT

This paper describes the benefits of using performance based geosynthetic testing for a copper-gold tailings storage operation in South Australia. This particular location requires strict environmental controls in a sensitive environment. Consultation occurred early during the approvals process to provide geosynthetic design guidance on the tailings storage facility site and design which had been selected. The regulatory requirements had two aims. The first was to provide a primary under-drainage collection system and the second was to provide a low permeability barrier in the form of a clay liner or geomembrane...

Resilience of Australian polymer-modified powdered sodium bentonite geosynthetic clay liners to downslope bentonite erosion

W. Gates, D. Gibbs, M. Amstberg

ABSTRACT

Loss of bentonite from geosynthetic clay liners (GCLs), installed as a component of a composite liner beneath an exposed geomembrane (GM) on the side-slopes of landfills and exposed to thermal cycling, has become a topic of some importance recently as it raises questions on the long-term durability of modern landfill lining products. Laboratory drip testing was used to evaluate the resilience of four GCLs containing polymer-modified powdered bentonite against down-slope bentonite erosion. Onset erosion features were observed only after 60-140 drip cy-cles...

Saline – Sodic Resistant Bentonite in Geosynthetic Clay Liners: Potential for Coal Seam Gas Applications

M.Gardam, W. P. Gates, W. Hornsey, J. Buckley and D. T. Gibbs

ABSTRACT

The handling, intermittent storage and disposal of saline-sodic brines, such as from coal seam gas (CSG) production, can adversely impact the hydraulic performance of clay-based barrier systems. The scarcity of suitable and economical clayey soils for traditional compacted clay liners throughout CSG localities in Australia has resulted in an increased use of geosynthetic clay liners (GCLs) to ensure environmental containment of process waters because of their technical equivalence, ready availability and ease of deployment compared to traditional clayey liners...