Instrumentation of soil columns for time-lapse monitoring of the phenomenon of capillary rise through spontaneous potential, soil moisture sensor, electrical resistivity, and GPR measurements

Abstract

The continuous monitoring of capillary rise via indirect measures aims to predict and generate alerts regarding the soil mass deformations, transport leachate from landfills to the soil surface, and carry salts that can damage buildings. Through time-lapse monitoring of the electromagnetic wave's electrical potential and speed, it is possible to correlate via petrophysical relations the measures of electrical potential, electrical resistivity, and dielectric permittivity to the volumetric water content and capillary height. For this, four acrylic columns filled with civil construction material were instrumented. Column 1 - silver electrodes to measure the potential difference with a bench multimeter that measures the spontaneous potential generated by water flow. Column 2 - low-cost soil moisture sensors that measured the electrical potential and converted to bits. Column 3 - resistivimeter that measured the voltage and that was later converted to electrical resistivity and, Column 4 - 2.6 GHz antenna that measured the speed of the electromagnetic wave that was later converted into dielectric permittivity. The instrumentation assembled proved to be satisfactory to monitor the phenomenon. The monitoring lasted 187 h, and it was found that the maximum capillary height remained constant for a long time.