A series of tests has been carried out on crude unprocessed household waste
in a large purpose-built compression cell, to investigate the variations i
n density, drainable porosity and hydraulic conductivity with vertical stre
ss. An increase in the particle density of the waste with increasing stress
was identified; this may mean that the applicability of some standard soil
mechanics theories to household waste may need to be reviewed. The results
of the tests are described and discussed, with reference to their implicat
ions for the how and control of leachate in landfills. The hydrogeological
limitations on vertical flushing rates in landfills operated as flushing bi
oreactors are considered and the operation and performance of leachate extr
action wells investigated by means of simple analytical models.