Recent developments in the direct-current geoelectrical imaging method

Detection of sinkholes using 2D electrical resistivity imaging

Detecting, real-time monitoring and early warning of underground water-bearing structures are critically important issues in prevention and mitigation of water inrush hazards in underground engineering. Direct current (DC) resistivity method is a widely used method for routine detection, advanced detection and real-time monitoring of water-bearing structures, due to its high sensitivity to groundwater. In this study, the DC resistivity method applied to underground engineering is reviewed and discussed, including the observation mode, multiple inversions, and real-time monitoring. It is shown that a priori information constrained inversion is desirable to reduce the non-uniqueness of inversion, with which the accuracy of detection can be significantly improved. The focused resistivity method is prospective for advanced detection; with this method, the flanking interference can be reduced and the detection distance is increased subsequently. The time-lapse resistivity inversion method is suitable for the regions with continuous conductivity changes, and it can be used to monitor water inrush in those regions. Based on above-mentioned features of various methods in terms of benefits and limitations, we propose a three-dimensional (3D) induced polarization method characterized with multi-electrode array, and introduce it into tunnels and mines combining with real-time monitoring with time-lapse inversion and cross-hole resistivity method. At last, the prospective applications of DC resistivity method are discussed as follows: (1) available advanced detection technology and instrument in tunnel excavated by tunnel boring machine (TBM), (2) high-resolution detection method in holes, (3) four-dimensional (4D) monitoring technology for water inrush sources, and (4) estimation of water volume in water-bearing structures.

Detecting and monitoring of water inrush in tunnels and coal mines using direct current resistivity method: A review

Detection of illegal mine voids using electrical resistivity tomography: The case-study of Raniganj coalfield (India)

Mineshaft imaging using surface and crosshole 3D electrical resistivity tomography: A case history from the East Pennine Coalfield, UK

The bulk of the worldi?½s platinum production originates from the Merensky and UG2 reefs within the Bushveld Complex, South Africa. Both the Merensky and UG2 reefs are disrupted by faults, dykes, potholes and iron-rich ultramafic pegmatite bodies (IRUPs)i?½ features that impact negatively on production, planning and safety. It is therefore advantageous to know of their presence and geometry ahead of mining. To date, no geophysical technique has been successfully applied to the routine mapping of mine-scale potholes and IRUPs. These disruptive features may vary from a few metres to several tens of metres in diameter. In this paper the applicability of in-mine electrical resistance tomography (ERT) to map potholes and other disruptions to the continuity of the Merensky and UG2 reefs ahead of mining is demonstrated using two case studies.

The application of in-mine electrical resistance tomography (ERT) for mapping potholes and other disruptive features ahead of mining

High-resolution crosshole imaging techniques are proving to be useful tools for mapping out mineralisation between exploration boreholes. Radio Tomography (RT) and electrical resistivity tomography (RESTOM) surveys were conducted at a disseminated sulphide test site in South Africa. The RT and RESTOM results correlate well, but contradict the existing interpretation as inferred from geological logs. It is concluded that the integrated application of high-resolution crosshole imaging techniques could play a major role in second-phase base metal exploration.

Comparison of crosshole radio imaging and electrical resistivity tomography for mapping out disseminated sulphide mineralisation at a surface test site in Mpumalanga, South Africa

Some of the recent advances in ground penetrating radar (GPR) technology are discussed in this paper; in particular the move to, and potential value addition offered by, the 3D approach to surveying over the more conventional 2D approach. Case studies at two platinum mines in the Bushveld Complex are used to stress the fact that the niche role for GPR is that of immediate hangingwall assessment, aimed at identifying geological features that could potentially result in falls of ground (FOGs). The paper also highlights the obstacles that still need to be overcome to enable GPR to become a routine tool in local mining operations, and recommendations are offered on how to address these obstacles through ongoing research efforts.

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The use of 3D ground penetrating radar to mitigate the risk associated with falls of ground in Bushveld Complex platinum mines

Copyright: SAIMM publishers. 2014. The application of geophysics in South African coal mining and exploration. The Journal of the Southern African Institute of Mining and Metallurgy, Vol 114, pp 875-879. Due to copyright restrictions, the attached PDF file only contains the abstract of the full text item. For access to the full text item, please consult the publisher's website

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M. van Schoor

Papers

The application of in-mine electrical resistance tomography (ERT) for mapping potholes and other disruptive features ahead of mining

Comparison of crosshole radio imaging and electrical resistivity tomography for mapping out disseminated sulphide mineralisation at a surface test site in Mpumalanga, South Africa

The use of 3D ground penetrating radar to mitigate the risk associated with falls of ground in Bushveld Complex platinum mines

The application of geophysics in South African coal mining and exploration