Theoretical and Experimental Investigations for Cavity Research With Geoelectrical Resistivity Methods*

Abstract

The exact localization of subterranean cavities and the determination of their dimensions is very important for the planning of geotechnical and mining activities. It is a complicated geophysical task often at the limit of detection. Nevertheless geophysical investigation is the only alternative to a dense and expensive grid of boreholes. This report tests the usefulness of geoelectrical resistivity methods for cavity detection under some new aspects. The basis for evaluation was a theoretical analysis of different conventional and focussing measuring arrays and of special arrays for a geoelectrical research between two boreholes. The limit of detectability of a cylindrical cavity of defined cross‐section and depth was calculated for the different measuring arrays on the basis of computation of the apparent resistivity ρa. Furthermore, the influence of possible errors (current supply of the electrodes and the distance between the electrodes) is discussed for focussed systems. The second part of the article is directed at the behaviour of the apparent resistivity ρa, the disturbing potential δVd caused by the cavity and the normal potential δV0 of the measuring array all in relation to a homogeneous earth. Some new results are presented. In the last part of the article theoretical results are compared with some field measurements.

Proceedings of tunnel detection symposium on subsurface exploration technology (4th) held in Golden, Colorado on 26–29 Apr. 93

“…There have been a wide range of successes and failures in the approach to this problem, and perhaps the only statement which can be made with certainty is that there exists no single technique which will address all situations at all times. Therefore, an integration of several geophysical sensing methods seems to be the most prudent approach to the problem (Friedel andHanson, 1990, andMilitzer, et al, 1979). Complexities in detecting voids arise due to variable target depth, changes in fill material (water, mud, air, etc.…”

“…Certain resistivity methods also have a history of successful applications to the cavity detection problem (Militzer, et al, 1979). It has been stated (Bristow, 1966) that voids are detectable at depths of up to 100 feet, depending upon size and fill material, using resistivity techniques.…”

High-resolution shear-wave seismic reflection as a tool to image near-surface subrosion structures – a case study in Bad Frankenhausen, Germany

“…To monitor sinkhole development, ortho-rectified aerial photos and differential field GPS are used Abelson et al, 2006), while the vertical displacement is detectable by radar interferometry Abelson et al, 2003) and plane-table leveling (Scholte, 2011). Gravimetric methods are suitable for the detection of cavities and mass movement (Arzi, 1975;Neumann, 1977;Butler, 1984;Benson et al, 1995), but they also deliver information about possible cavity fills, as do geoelectric (Militzer et al, 1979;Bataynek and Al-Zoubi, 2000;Miensopust et al, 2015) and geomagnetic (Bosch and Müller, 2001) methods. Analogue and digital mechanical modeling of the development and the propagation of collapse sinkholes is also a valuable tool (Abdulla and Goodings, 1996;Tharp, 1999;Augarde et al, 2003).…”

Detection of underground cavities using microtremor: physical modeling

“…Из электроразведочных методов наибольшее рас-пространение при локализации подземных пустот по-лучили различные модификации метода сопротивле-ний [Militzer et al, 1979;Pánek et al, 2010;MartinezPaganet et al, 2013]. В силу резкого контраста прово-димости пустот и вмещающих пород этим методом во многих случаях могут быть получены хорошие резуль-таты.…”