Improved Measurement of Soil Moisture and Groundwater Level Using Ultrasonic Waves

Field monitoring of soil moisture and groundwater levels is one of the countermeasures against slope failure caused by heavy rainfall. We developed a new monitoring method for soil moisture and groundwater level using ultrasonic waves. An ultrasonic detector in this measuring method is easily installed underground and at low cost, and therefore, this method is useful for multipoint monitoring in a wide field area. However, since the measurement data are greatly influenced by temperature, this temperature-dependent effect must be corrected. Previously, the dummy pair system using two detectors had solved this problem. In this paper, we propose another improved temperature correction method using one detector and evaluate the usefulness of both methods in detail.