Monitoring of Soil Moisture and Groundwater Level Using Partially Embedded and Completely Embedded Ultrasonic Detectors to Predict Slope Failure

Field monitoring of soil moisture and the groundwater level is important in predicting slope failure due to heavy rainfall. We investigated the use of ultrasonic waves for monitoring these conditions. Two methods for embedding the ultrasonic detector in the ground were investigated: partial embedding and complete embedding. With partial embedding the detector head and electrical connection are above ground and the lower part of the detector is in the ground. This type of embedding is easy, but disturbs the landscape and the detector is subject to vandalism and animal damage. With complete embedding the detector and electrical connection are both in the ground, with nothing exposed. This eliminates the problems mentioned. To enable the use of a short detector that can be completely embedded, high frequency (95 kHz) ultrasonic waves are used. Indoor experiment demonstrated that a completely embedded short detector using 95-kHz waves can monitor soil moisture and the groundwater level and thus be used in predicting slope failure.