Long term settlement behaviour of dump wastes in Sri Lanka : case study on bloemendhal dump site

Abstract

Open dumping has been widely used to dump wastes in developing countries. In Sri Lanka, most of the dumpsites are open dumpsites. Due to high demand for lands, previously abandoned lands are now utilized for construction activities. However, due to heterogeneity and variability, construction or performance on these type of lands requires more studies. Therefore, settlement characteristics of dump waste are needed to be studied. This research paper discusses about long-term settlement behaviour of dump waste. Secondary compression is due to creep of the waste skeleton and biological decay. In general, secondary compression accounts a significant part of total settlement of dump area and it may occur over many years. This research was carried out to find settlement parameters of Bloemendhal dumpsite. According to the Unified Classification System, this sample was classified as well graded sand with silt and gravel (SM-SM). Standard Proctor compaction test reveals that, the sample has maximum dry density of 1418 kg/m3, which is lower value compared to a traditional lateritic soil in Sri Lanka. Optimum moisture content is 24.5%. Primary consolidation parameters were evaluated through laboratory experiments. Sample has the coefficient of consolidation in the range of 1 - 4 m2/year and coefficient of compressibility in the range of 0.05 – 0.1. The sample has lower secondary consolidation creep index, which is in the order of 10-3. However, it is strongly suggested to study the long term biodegradation studies on fresh dumpsite samples.