Analysis of the in situ constant-head permeability test in clays

The in situ measurement of soil permeability has become an important part of geotechnical engineering. New equipment has made the execution of in situ constant-head tests simple and reliable. However, the theories used for the interpretation of constant-head tests in low-permeability soils still present some shortcomings. A finite element analysis of the constant-head test in clays is carried out to evaluate the various expressions of shape factor published in the literature and to provide a basis for extrapolating transient state observations to steady state conditions from which the permeability may be computed. The resulting method of interpreting in situ permeability tests is applied to series of field results obtained from a Champlain clay deposit. Key words: clay, permeability, constant-head test, in situ test, shape factor, finite element analysis.