Study on the strength characteristics of MSW in Sri Lanka

Abstract

Proper engineering landfills have not been practiced by Sri Lanka. Most of the open dumps in the country are located in the city centers. Due to rapid development and urbanization, these dump sites are abandoned and now they are used for critical construction works. Strength characteristics are very important for general foundation designs, however, due to the heterogeneity, it is very difficult to evaluate those parameters in dump waste sites. Dump waste samples were collected from Bloemendhal dumpsite. Direct shear test and unconsolidated undrained tri axial tests were conducted to obtain the shear strength properties such as cohesion and angle of friction for different moisture contents obtained during Proctor compaction test. Direct shear tests have proven that the angle of internal friction does not vary much with moisture content. However, the experimental results of cohesion of dump wastes haveshown that the cohesion of dump waste varies with moisture content and the shape of the cohesion vs moisture content graph is similar to the shape of the Proctor compaction test. These results indicate that the behavior of the dump wastes is similar to silty soil. Further tests were done with the addition of cement to observe the strength gain. Several cement contents were tested and unconfined compression tests were carried out on the wetted (cured) samples with time until 28 days. Samples were tested at certain time intervals and observed the strength gain with time. Age of the solid waste could change the properties of MSW. However, in this study it has to be noted that the age could not be used as an external parameter as the open dumps had been operated without proper records.