A Review on Applications of Time-Lapse Electrical Resistivity Tomography Over the Last 30 Years : Perspectives for Mining Waste Monitoring

Abstract

Mining operations generate large amounts of wastes which are usually stored into large-scale storage facilities which pose major environmental concerns and must be properly monitored to manage the risk of catastrophic failures and also to control the generation of contaminated mine drainage. In this context, non-invasive monitoring techniques such as time-lapse electrical resistivity tomography (TL-ERT) are promising since they provide large-scale subsurface information that complements surface observations (walkover, aerial photogrammetry or remote sensing) and traditional monitoring tools, which often sample a tiny proportion of the mining waste storage facilities. The purposes of this review are as follows: (i) to understand the current state of research on TL-ERT for various applications; (ii) to create a reference library for future research on TL-ERT and geoelectrical monitoring mining waste; and (iii) to identify promising areas of development and future research needs on this issue according to our experience. This review describes the theoretical basis of geoelectrical monitoring and provides an overview of TL-ERT applications and developments over the last 30 years from a database of over 650 case studies, not limited to mining operations (e.g., landslide, permafrost). In particular, the review focuses on the applications of ERT for mining waste characterization and monitoring and a database of 150 case studies is used to identify promising applications for long-term autonomous geoelectrical monitoring of the geotechnical and geochemical stability of mining wastes. Potential challenges that could emerge from a broader adoption of TL-ERT monitoring for mining wastes are discussed. The review also considers recent advances in instrumentation, data acquisition, processing and interpretation for long-term monitoring and draws future research perspectives and promising avenues which could help improve the design and accuracy of future geoelectric monitoring programs in mining wastes.

Keywords: Early warning systems; Geotechnical and geochemical stability; Mining wastes monitoring; Remote autonomous monitoring; Time-lapse electrical resistivity tomography.

Fig. 1

Diagram of an open-pit mine operation and simplified mass balance of wastes and minerals

Fig. 2

Distribution and surface of mining waste storage facilities across Canada in 2020 Each mining site in Canada (active, closed or abandoned) has been identified and the areas occupied by TSFs, WRPs and open-pits have been calculated with Google Earth satellite imagery. The database and interactive maps can be accessed and downloaded through https://adridim.github.io/review2022/0_welcome.html

Fig. 3

Example of TL-ERT monitoring of a tracer infiltration with surface and borehole electrodes. (i) Top panel shows the true spatio-temporal distribution of tracer concentration in the medium, (ii) medium panel presents the corresponding distribution of electrical resistivity and (iii) the inverted distribution of resistivity obtained from TL-ERT monitoring. Finally, (iv) bottom panel shows the ERT-predicted tracer concentration using petrophysical relationship (based on Singha et al. (2015))

Fig. 4

Spatio-temporal parameters of TL-ERT surveys (inspired from Rucker (2014))

Fig. 5

Diagram of ERT inversion routine used to reconstruct distribution of electrical resistivity $\rho$

Fig. 6

Review of the main applications of TL-ERT for various domains

Fig. 7

General statistics for each field of applications identified in the database of TL-ERT studies : a evolution of the number of published studies per year from 1991 to 2020 for each type of application and b distribution of the 651 published studies according to the classification proposed in Fig. 6. Note that the identification of TL-ERT studies has been carried out during Summer 2020, which explains the relatively low number of publications identified for 2020 (shaded)

Fig. 8

Review of the main applications of ERT for mining wastes imaging and monitoring

Fig. 9

Review of the key parameters that can be imaged or monitored in WRPs with TL-ERT as identified from the database of ERT studies in mining wastes (adapted from Aubertin et al. (2005))

Fig. 10

Review of the key parameters that can be imaged or monitored in TSFs with TL-ERT as identified from the database of ERT studies in mining wastes (adapted from Aubertin et al. (2016))

Fig. 11

Recent developments and perspectives for geoelectrical monitoring of mining wastes

Fig. 12

a Evolution of the number of electrodes, the monitoring period and the temporal resolution for the 173 semi-permanent TL-ERT studies identified in the database. For each study, the size of the circle is proportional to the monitoring period while the color of the circle corresponds to the temporal resolution. b Histogram of semi-permanent TL-ERT studies according to the temporal resolution

Fig. 13

Flowchart of permanent TL-ERT monitoring system describing autonomous data acquisition, remote data transfer, automated processing and interpretation for long-term monitoring. Figure inspired from Holmes et al. (2020) presenting the workflow of the PRIME system applied to landslide monitoring in British Columbia (Canada)