Determination of Porosity Distributions of Water Saturated Granular Media Using Spatial Time Domain Reflectometry (Spatial TDR)

A sensor has been developed for the investigation of erosion processes in cylindrical specimens that permits the determination of porosity distributions using spatial time domain reflectometry (spatial TDR). Spherical glass beads saturated with water were used as a model material. The porosity was varied by mixing different size glass beads, and a physical mixing rule was optimized to determine a temperature dependent calibration function between dielectric permittivity and porosity. Homogeneous specimens were used to calibrate the sensor. An inversion algorithm was used for the analysis of the TDR signals. Both the sensor and the procedure were tested using specimens of glass beads comprised of layers with different porosities. The comparison between the measured and predefined porosity distributions shows satisfactory agreement.

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