Abstract:
Open dumping is the most prevalent method of waste disposal in Sri Lanka. These sites, which are
currently used as waste dump yards in urban areas, will have to be rehabilitated to be converted to
be used as parks, roads or for other different construction projects. Establishing the strength and
stiffness characteristics of these waste materials at different levels of degradation and how these
characteristics can be enhanced to suit the proposed developments is a major challenge. The
mechanisms of settlement that govern the solid waste material are numerous and complex.
Bowders et al. (2001) reported that there are many reasons behind this behaviour of waste such as
extreme heterogeneity of the wastes, their own particle deformability, the large voids present in
the initial waste fill, and their biodegradability. According to Watts and Charles (1990) and
Manassero et al. (1996), the settlement behaviour of MSW is often classified as occurring in
several distinct phases. Primary consolidation of solid waste occurs due to the self-weight of the
waste or application of surcharges such as fill over the time. Primary compression is then followed
by the secondary compression. Secondary compression occurs due to biodegradation process in
waste fill, and it can take years for this settlement to complete depending upon various phases of
waste that it consists of.
This paper presents a study of the effectiveness of dynamic compaction as a technique of
enhancing the compressibility characteristics of waste dumps. MSW was subjected to dynamic
compaction in a laboratory test setup, and another MSW sample was kept uncompacted. Next,
MSW samples in both compacted as well as in non-compacted state were subjected to loading in
a Rowe Cell of diameter 150 mm and height 50 mm and results were analysed to establish the
compressibility characteristics, namely coefficient of volume compressibility (mv),
compressibility index (Cc), coefficient of consolidation (Cv) and coefficient of secondary
compression (Cα). Finally, results were compared to assess the effect of dynamic compaction on
compressibility characteristics of MSW and the effectiveness of the process is compared with that
of preloading.
Compression index of MSW that was subjected to dynamic compaction was reduced to about 50%
of the compression index of the non-compacted MSW. Recompression index values of noncompacted
MSW values are less than about 10% of compression index values of non- compacted
MSW samples. Similarly, results obtained for coefficient of volume compressibility shows greater
reduction by preloading compared to dynamic compaction. Both preloading and dynamic
compaction show significant effectiveness in reducing the coefficient of secondary consolidation.
In conclusion, compressibility characteristics of MSW can be improved significantly using both
preloading and dynamic compaction. According to results observed in this study preloading can
be considered as the more effective method. However, depending on the composition and the
degradation level of the MSW sample used these results can be changed. Considering the time, it
takes to achieve the required compressibility reductions by preloading, dynamic compaction can
be considered as another advantageous option.
Citation:
Rathnayaka, R.I.A., & Kulathilaka, S.A.S. (2021). Improvement of compressibility characteristics of waste material by dynamic compaction [Abstract]. In P. Hettiarachchi (Ed.), Proceedings of Civil Engineering Research Symposium 2021 (p. 35). Department of Civil Engineering, University of Moratuwa.