Identification of initial settlement of municipal solid waste layers in Indonesian landfill

This study presents the measurement of municipal solid waste (MSW) compressibility and subsequent development of a landfill settlement estimation model incorporating a correction factor accounting for initial settlement prior to the addition of pressure/municipal solid waste layers. Three layers of municipal solid waste obtained from a temporary waste station in Bandung, Indonesia, were placed in each of three different lysimeters/treatments (MSW_organic, layer height 35 cm; MSW_mixed-1, layer height 70 cm; and MSW_mixed-2, layer height 35 cm), with a time lag of sample layer input of 2 days. Tests were then undertaken based on the ASTM D2435 test standard – Standard Test Method for One-Dimensional Consolidation Properties of Soils – revealing large immediate and secondary compression ratio values reflecting the high moisture and organic matter content of the analysed municipal solid waste. From the test results, it was also detected that the initial settlement of the analysed municipal solid waste was considerable even before the addition of pressure/further layers, ranging from 10% to 17%. Thus, a modification was made to the classical Sowers settlement estimation model in the form of a correction factor representing the initial settlement occurring prior to the addition of the municipal solid waste layers. This modification resulted in a decrease in the difference between estimated and actual settlement values, from 17% to 24% based on the Sowers equation model to below 5% using the proposed modified settlement model.