ABSTRACT:

The suitability of paper mill and construction sludges as landfill cover materials has been examined in view of the scarcity of natural clay sources and reducing waste disposal cost at landfill sites. The results of consolidation, shear strength and hydraulic conductivity tests have been investigated to predict the engineering behaviour as well as long term performance of sludge samples. The present study encourages the possibility of using above-mentioned waste sludges as an alternative for landfill cover materials.

INTRODUCTION

Recently the waste management problem in Japan has become a serious concern, and there is a need to reuse the wastes in an effective way to minimize its disposal. The paper industries in Japan produce large amount of sludge (1.15 million tons) every year, and the disposal of above waste is a serious concern (Kamon and Katsumi 1994). The amount of waste sludge (CS) produced from construction works has reached a level of 10 million tons per year due to slurry excavation methods associated with diaphragm walls, shield tunnel and cast-in-place concrete pile works. When compared with the total quantity of CS generated, the amount of recycling (2%) is low since CS slurries contain fine soil particles (including bentonite), which make it difficult to dehydrate. As per the Japanese legal system, PMS and CS are considered waste, and have to be disposed of in landfills. The present landfill sites will be exhausted in the near future, and hence new methodologies should be developed for reuse of above sludges in an effective way. Several investigators have made an attempt to utilize CS and PMS for geotechnical applications (Kawachi et al. 1996; Kamon et al. 1999). In Japan, no study on the use of CS and PMS in landfill cover applications has been reported.

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