Abstract
Frequency-dependent streaming potential coefficient measurements have been made upon Ottawa sand and glass bead packs using a new apparatus that is based on an electromagnetic drive. The apparatus operates in the range 1 Hz to 1 kHz with samples of 25.4 mm diameter up to 150 mm long. The results have been analysed using theoretical models that are either (i) based upon vibrational mechanics, (ii) treat the geological material as a bundle of capillary tubes, or (iii) treat the material as a porous medium. The best fit was provided by the Pride model and its simplification, which is satisfying as this model was conceived for porous media rather than capillary tube bundles. Values for the transition frequency were derived from each of the models for each sample and were found to be in good agreement with those expected from the independently measured effective pore radius of each material. The fit to the Pride model for all four samples was also found to be consistent with the independently measured steady-state permeability, while the value of the streaming potential coefficient in the low-frequency limit was found to be in good agreement with other steady-state streaming potential coefficient data.
Highlights
There have only been 10 measurements of the frequencydependent streaming potential coefficient of porous geological and engineering materials
The equations that describe the streaming potential coefficient are linear below the transition frequency and there is no evidence that they become nonlinear above that frequency, it has not yet been shown that such an approach can be made to work for streaming potential coupling coefficient measurements on rocks
This paper reports research that uses the electromagnetic drive concept proposed by Glover et al [1] to create an apparatus for measuring the frequency-dependent streaming potential coupling coefficient of unconsolidated materials such as sands, gravels, and soils
Summary
There have only been 10 measurements of the frequencydependent streaming potential coefficient of porous geological and engineering materials. While the first of these approaches mimics many of the possible applications more closely [2,3,4], it cannot provide the streaming potential coupling coefficient as a function of frequency without using the frequency domain filtering and Fourier techniques Such techniques can only be used in a linear system. This paper reports research that uses the electromagnetic drive concept proposed by Glover et al [1] to create an apparatus for measuring the frequency-dependent streaming potential coupling coefficient of unconsolidated materials such as sands, gravels, and soils. The theoretical models have been compared with the measured data in order to obtain the transition frequency, which has been used to calculate the effective pore radius of the sands and glass bead packs using the theory in Glover and Walker [12]
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