Karst Detection Using Low-Cost Electrical Resistivity Meter

About one-fifth of the United States is underlain by soluble rock and has the potential to develop voids within the subsurface (karst). It has been shown that property damages resulting from sinkhole formation in karst terrain amount to hundreds of millions of dollars each year. Different geophysical investigations (investigation methods that do not require any digging), are commonly employed to assess the potential risk of karst. However, most geophysical equipment from commercial vendors has very complex inner workings and costs tens of thousands of dollars. The present work extended the previous understanding on the fabrication of low-cost electrical resistivity (ER) meters and proposed the design of a new prototype to perform independent ground surveys. The developed device implemented inexpensive, user-friendly integrated circuit modules able to inject a current, measure the site’s response, and characterize the local properties of soil and rock. The reliability of this ER meter was assessed using a series of test resistors. In this confirmatory test, the device proved to be accurate over a wide range of magnitudes. This ER meter also showed the potential for many practical applications. In a tabletop laboratory setting, the prototype successfully sounded overlying soil covers and correctly identified the lateral variations in apparent resistivity values along a transverse. The results from this study indicate that low-cost ER meters are capable of detecting underground discontinuities such as voids in an effort to prevent sinkhole formation in karst-prone areas.