Evaluating interface properties of geomembrane and compacted clay liners for landfill liner stability
Majority of failure occurs within waste mass and along landfill liners. This paper will discuss the methods adopted to study landfill liner interface performances. Interfaces shear strength parameter evaluation for landfill liner systems have been a tedious testing process. Various testing methods and guidelines have been proposed by engineers and researchers over the years. The current testing procedures are based on ASTM testing guideline and basic fundamental engineering testing philosophies. Hence there is a need for much ideal testing equipment which can perform the entire test series required for landfill liner parameter evaluations.
The equipment are required to perform interface test between:
- Soil and soil (CCLs)
- Geomembrane (HDPEs and PVC)
- Geosynthetic (GCLs) / compacted clay liners (CCLs) and soil
- Geomembrane and geotextile
- Geotextile and soil
- Geotextile and geosynthetic (GCLs) / compacted clay liners (CCLs)
- Geomembrane and geosynthetic (GCLs) / compacted clay liners (CCLs)
Having such variety in requirement and testing complexity for landfill liner system, this paper also addresses the modification made to a large scale shear box in order to perform the above said interface tests. The shear box is modified to perform interface test under wet condition and at optimum condition. However data of optimum conditions are presented herewith. The modified large scale shear box is used to study interface performance of various combination of liners. Two common type of compacted clay liners (CCLs), which are silt bentonite mixture (100 : 10) and sand bentonite mixture (100 : 10), studied together with geomembrane. The interface parameter data are then compiled to be a quick reference guide for engineers.
The world consumption of natural resources has been increasing exponentially. In Japan the consumption of resource is at 1900 million tones annually. This consumption generates waste of 600 million tones, which consist of 400 million tons of industrial waste and 50 million tons of municipal waste. Out of this 220 million tons are recycled and reused, 324 million tons are pre-treated waste for disposal. 56 million tons are disposed to landfill in Japan in year 2000. The estimated operational period of landfill site in Japan is about 6 to 10 years.
It becomes very difficult to build new sites in Japan due of the syndrome of “Not In My Back Yard”. The cost of new site in Tokyo could cost up to 500 million US dollars. The Running cost of existing landfill site in Tokyo is at about 300 USD / m3. A landfill also behaves as in-situ bioreactor, where the contents undergo complex biochemical reactions. The adoption of suitable design and construction methods are essential not only to reduce design and construction cost, but also to minimize long term operation, maintenance and monitoring cost.
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