Study on the geotechnical properties of open dumps in Sri Lanka

Abstract

Municipal Solid Waste (MSW) is an area which has got the attention of geotechnical engineers currently with their researches, due to the requirement of land in order to cater increasing population. Therefore, the focus of this study has been on the MSW dumping yards to be used as construction sites. Even though there have been researches all over the world regarding the characteristics of MSW with respect to geotechnical engineering properties due to the variations of the compositions of MSW, degradation conditions etc: all those results cannot be readily applied in Sri Lankan conditions under the uncontrolled landfills. Therefore this research study has been carried out to determine the properties of three dump yards in Sri Lanka, with respect to their strength parameters, compaction characteristics and compressibility characteristics. Particle size distribution tests carried out on the collected samples showed that almost all the samples are having a particle size distribution quite similar to coarse grained soils, with F0.075 in the range of 10% -20%. Standard Proctor compaction test gave maximum dry densities in the range of 1000 – 1500 kg/m3 for these samples, which are sometimes low compared to traditional lateritic soils in Sri Lanka. Optimum moisture contents corresponding to those Proctor compaction tests were lying in a range of 22% to 40%. Further, working range of the moisture content for these samples was wider than traditional soils, which ranged in between 15% to 50% for almost all the cases. Direct shear (DS) tests carried out on the samples with different moisture contents, as in the Proctor compaction test showed that the variation in the friction angle (°) was less compared to the variation of the cohesion parameter (c kN/m2) with different moisture contents. Range for ° was in between 18 – 21 as a whole, while the cohesion ranged between 10 kN/m2 and 25 kN/m2. Tests carried out in finding the compressibility characteristics of MSW mainly focused primary consolidation, which gave results in the range of traditional soils. However, further long term studies should be carried out prior coming up with conclusions with respect to the compressibility characteristics of MSW in Sri Lankan context.