The Stability and Settlement of Municipal Waste Landfills

Municipal waste is another non-textbook material, generally highly fibrous, heterogeneous, erratic, highly compressible, and displaying significant long-term settlement caused by plastic creep and decomposition. On the basis of the review of a number of case records, neither undisturbed sampling nor field testing is practical. On the other hand, since displacement is often the critical issue and since displacements are measurable in situ, it would seem that the use of a remote sensing system of direct measurements should be adopted where such displacements are critical. Sampling of strongly decomposed waste may be problematic because of caving problems. Conventional laboratory testing methods cannot generally be used, because the structure of the waste in the field is really indeterminate, and cannot therefore be reliably duplicated in the laboratory. Also, the pronounced fibrosity of the samples renders conventional testing of dubious value, generally yielding misleading results. Another important consideration is the fact that waste is subject to decomposition and that the stipulation of constant strength parameters like cohesion and friction is therefore not valid. This consideration appears to be largely disregarded by the profession.