EVALUATION OF INSITU PERMEABILITY TESTING METHODS

A testing program was established to determine the accuracy and efficiency of in situ permeability testing equipment. The sealed single-ring infiltrometer, sealed double-ring infiltrometer, and air-entry permeameter were evaluated in this study. The theoretical basis for each of these tests was examined and their testing procedures outlined. The accuracy and ease of use of these devices was demonstrated by full-scale tests under controlled field and laboratory conditions. The field permeability tests were conducted on a residual soil-liner test pad installed at a site near Jamestown, California. The laboratory permeability tests were conducted on a prototype liner composed of uniform Ottawa sand and sodium bentonite. This material was mixed, moisture-conditioned, and compacted into reinforced wooden frames. The in situ permeability test results were verified with low-gradient, back-pressure saturated triaxial permeameter tests conducted on undisturbed 101.4 mm (4 in.) cored and remolded samples. This evaluation shows that good agreement can be obtained between in situ field and laboratory triaxial permeability tests results. In addition, changes in hydraulic conductivity of hydrating sand-bentonite with time observed in the in situ tests, closely approximated the results obtained in the triaxial permeability tests. This evaluation also demonstrated that considerable care was required setting up and conducting in situ permeability tests, in order to obtain reliable results. © ASCE.