Laboratory experiment of the tomography measurement using a new microchip soil moisture sensor

Abstract

Conventional commercial soil moisture sensors measure only in the vicinity of the sensor prongs, thus, provide a values of a “point”. This study, using multi-modal microchip sensors (impedance, phase and temperature), aims to establish a tomographic method to elaborate the point data for estimating the two-dimensional distribution of soil moisture. Infiltration and drainage were simulated using a soil tank in the laboratory to evaluate performance of a vertical gravel drain in a highway embankment. The water flow in the soil tank was monitored by the new microchip sensors and commercially available capacitance-based soil moisture sensors. The results showed that the point values and those between the sensors partly agreed with the point and areal average values from the capacitance sensors. The rest of the results, however, showed a significant discrepancy between the two sensor types. It indicated a need for a further close examination of presence and effects of heterogeneity in the soil tank, as well as the differences in sensors’ measurement characteristics.