Journal Published Online: 01 December 1989
Volume 12, Issue 4

Graphical Method for Determining the Coefficient of Consolidation c from a Flow-Pump Permeability Test



A graphical method has been developed for determining the coefficient of consolidation from the transient phases of a flow-pump permeability test. The flow pump can be used to infuse fluid into or withdraw fluid from a laboratory sediment specimen at a constant volumetric rate in order to obtain data that can be used to calculate permeability using Darcy's law. When the initial transient-response curve (hydraulic head as a function of time) generated by this test is examined analytically in terms of a one-dimensional consolidation process, representative type-curve solutions to the associated forced-flow and pressure-decay models are derived. These curves provide the basis for graphically evaluating the permeability k, the coefficient of consolidation cv, and the coefficient of volume change mv. The curve-matching technique is easy and rapid, and it can be applied to results of forced-flow tests, both infusion and withdrawal, as well as to subsequent pressure-decay records. Values of k, cv, and mv for a laterally confined kaolinite specimen were determined by this graphical method and appear to be in reasonably good agreement with numerically derived estimates (within 20%). Discrepancies between the two sets of results seem to be largely a function of data quality rather than of method of analysis. Where responses of hydraulic head as a function of time are apparently unaffected by experimental sources of error, agreement is excellent (within 4%). Application of this graphical method to triaxial testing has inherent uncertainties, because the solution curves that describe one-dimensional deformation are used to analyze a three-dimensional process.

Author Information

Morin, RH
U.S. Geological Survey, Denver, CO
Olsen, HW
U.S. Geological Survey, Denver, CO
Nelson, KR
Colorado School of Mines, Golden, CO
Gill, JD
Colorado School of Mines, Golden, CO
Pages: 6
Price: $25.00
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Stock #: GTJ10989J
ISSN: 0149-6115
DOI: 10.1520/GTJ10989J