Realization and interpretation of field permeability tests in low-permeability materials

F. Duhaime

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: GROUNDWATER AND HYDROGEOLOGY - I Groundwater Hydraulics

ABSTRACT: Field permeability tests are conducted in low-permeability materials for several applications including waste disposal. They are typically initiated by changing rapidly the water level in a well riser pipe. Permeability can be calculated from the relationship between water level and time as the hydraulic head in the well equilibrates with that in the surrounding soil. This paper introduces the two main types of interpretation methods for field permeability tests. These two families are based on different assumptions regarding porous media compressibility. They either assume a linear relationship between pore volume and pore pressure, or a perfectly rigid soil skeleton. The paper shows how the type curves and interpretation procedures for the two families of interpretation methods differ and how they can be reconciled for tests involving small deformations. The paper also shows how the cavity volume change, a deformation component that is not usually considered, can be taken into account, and how the two types of interpretation methods can be unified with non-dimensional velocity graphs. Tests conducted in Champlain clay are used to exemplify the concepts presented in the paper. Recommendations are finally given on how to design field permeability tests that have a reasonable duration and that are not overly influenced by deformations.

RÉSUMÉ: Des essais de perméabilité in situ sont réalisés dans les matériaux peu perméables pour plusieurs applications incluant le stockage des déchets. Typiquement, ces essais sont démarrés en changeant rapidement écoulé pendant que la charge hydraulique dans le puits . Cet article expose les deux principales familles Ces deux familles sont basées sur des hypothèses différentes concernant la compressibilité du milieu poreux. Elles supposent soit une relation linéaire entre le volume des pores et la pression interstitielle, soit un squelette granulaire parfaitement rigidnt pour les deux types de méthodes et comment elles peuvent être ngement de prise en compte, peut être incorporée interprétation peuvent être unifiés avec le graphique adimensionnel des vitesses. Des essais réalisés danés pour illustrer les concepts article. Des recommandations sont finalement données afin de planifier des essais de perméabilité in situ qui aient une durée raisonnable et qui ne soient pas excessivement influencés par les déformations.

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