Hybrid Rowe cell for measurement of complex conductivity

Peat is sediment consisting of incompletely decomposed organic matter deposited in swamp and marsh. It has served for a long time as benefits for human beings. Meanwhile, it has posed huge challenges to geotechnical engineers because of its unique characteristics such as anisotropy, low stiffness, high compressibility and strong creep susceptibility. In order to realise more effective and efficient site investigations, it is highly expected to apply geophysical techniques as well as core-boring, CPTs, sampling and laboratory tests because the techniques promise to be great contributions not only for two- or three-dimensional mapping but also for accurate interpretation of its physical, chemical and engineering properties in non-destructive way. Then, a new apparatus has been developed, called hybrid Rowe cell. It combines the functions of a traditional hydraulic cell and an electrical capacitor. This can simultaneously measure electrical properties and physical, mechanical and hydrological properties of soil samples, allowing to investigate their correlation accurately. This work focuses on the study of the applicability and calibration of the new hybrid cell, and the relationship between electrical conductivities of bulk peat and pore water which saturates the sample. The applicability of the hybrid cell was examined by using water as calibration. The results were then compared with values reported earlier and the experimental set-up was also compared with similar one found in literature. As a result, it was proven that the new cell successfully prevented electrode polarization and was applicable for this type of measurements. The electrical measurements on peat showed a relationship between the electrical conductivities of bulk peat and pore water which could be well predicted by a model previously developed for peat as well as the modified Archie’s law. In addition, the modified Archie’s law could be considered to be a persuasive model for the electrical behaviours observed in this study. For the future research, it is highly expected that the frequency of input currents is extended to lower range (< 20 Hz), input electric currents are properly controlled to avoid non-linear effects, and also hydraulic consolidation tests are performed in parallel with electrical measurements.

Subject

Rowe cell
electrical conductivity
electrical double layer
induced polarisation
Archies law
peat
hydraulic conductivity

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Student theses

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master thesis

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