(a) For the low plasticity MM material, depending on initial conditions, AP permeability results were often significantly greater (2 or 3 orders of magnitude greater) than the results for BS tests carried out with the same average effective stress. (b) The stress paths followed in the BS and AP tests are significantly different, as are the end conditions. The AP specimens were saturated or near-saturated at the end of an AP tests but B values determined at the end of the test were often around 0.90. (c) The average effective stress has a marked influence on permeability values. The hydraulic gradient also has an influence on the MM materials. (d) Depending on initial conditions, swelling, elastic behaviour, yielding, irrecoverable plastic deformations, and collapse compression may be identified within the permeability tests. (e) The Environment Agency accepts the BS test as an appropriate means of assessing the permeability of mineral liners and cappings for landfill sites However, the sequential saturation, consolidation and permeability stages in a BS test are unlikely to be realised in practice. The potential variation in permeability results using different testing techniques is emphasised by the large variation in permeability recorded for the MM material using the BS and AP methods.
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