Real-time ultrasonic water level IoT sensor for in-situ soil permeability testing.

Soil permeability tests require a time series of water level measurements to determine system losses, including both infiltration and evaporation. Laboratory measurements of flow are standardised by international regulations such as ASTM International, ISO or UNE, but field measurements are not as well described and in some cases may require definition and specification of test conditions. This is the case for geosynthetic clay liner (GCL) products, where permeability is assessed by a laboratory measurement using a flexible wall permeameter as defined in standard test method D 5887-04. This method is not able to evaluate the performance of such products in the field and therefore cannot guarantee their ability to be used for the repair of landfill liner overlays. For this reason, we have defined a field test in a confined steel ring and developed a real-time ultrasonic IoT device to evaluate water losses over a period of time. The test method was applied in Mallorca (Spain) and as a result the quality of a landfill cover repair solution was evaluated, the corresponding civil works were carried out and the basis for future field measurements of soil permeability tests on different materials and conditions was established.