Application of electrical resistivity imaging to detection of hidden geological structures in a single roadway

Weihong Guo,Yaoning Liu,Shucai Liu,Shuangshuang Chen

doi:10.1515/geo-2020-0175

Weihong Guo, Yaoning Liu + Show 2 more

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https://doi.org/10.1515/geo-2020-0175

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Abstract

Abstract Locating concealed geological structures in coal seams on both sides of a coal mine excavation roadway is of vital importance for safe production. Conventional electrical resistivity imaging methods mostly arrange observation systems on the roadway roof and floor, so they are inevitably deficient when it comes to detecting concealed geological structures in coal seams. According to the electric field distribution characteristics of artificial field sources for electrical resistivity imaging methods and utilizing the shielding of current by roadway cavities, this paper proposes the parallel coal seam detection method that arranges observation systems in coal seams on the roadway side to detect concealed geological structures in coal seams. On the basis of introducing the principles of consequent detection methods, this paper investigates the influence of roadway cavities on observation results and offers a method of correcting the influence of roadway cavities. In view of the geoelectric characteristics of typical concealed geological structures in working faces, this paper establishes numerical models to verify the feasibility of the parallel coal seam detection method. As indicated by the calculation results, the consequent pole–dipole (A-MN) observation system is the most ideal in terms of dividing the geoelectric interfaces of concealed geological structures in working faces, and its detection effect is influenced significantly by the coal seam thickness and the electric differences between surrounding rock and anomalous bodies. Coal seam resistivity slightly influences detection of the consequent pole–dipole system. According to practical application effects, the parallel coal seam detection method can solve the problem of detecting concealed geological structures in “single-roadway” working faces.

Highlights

Faults, collapse columns, and other concealed geological structures existing in coal seams jeopardize coal seam continuity and affect roadway and working face layout but are extremely apt to cause water inrush or coal and gas outburst accidents when connected with an aquifer or a gas enrichment area
According to practical application effects, the parallel coal seam detection method can solve the problem of detecting concealed geological structures in “single-roadway” working faces
Collapse columns, and other concealed geological structures existing in coal seams jeopardize coal seam continuity and affect roadway and working face layout but are extremely apt to cause water inrush or coal and gas outburst accidents when connected with an aquifer or a gas enrichment area

Summary

Introduction

Collapse columns, and other concealed geological structures existing in coal seams jeopardize coal seam continuity and affect roadway and working face layout but are extremely apt to cause water inrush or coal and gas outburst accidents when connected with an aquifer or a gas enrichment area. In recent years, focusing on the differences between surrounding rock and concealed geological structures in coal strata in terms of electric properties, magnetic property, wave impedance, and other physical properties, a series of geophysical prospecting techniques have developed rapidly [1], primarily including: (1) ground electromagnetic methods that include: the DC electrical sounding method [2,3,4,5], highdensity resistivity method [6], and ground transient electromagnetic method [7] Methods of these types uniformly arrange field sources and receivers on the ground surface, have poor coupling with targets, and can satisfactorily resolve power shallow anomalous bodies; with increasing depth, the resolution drops rapidly [8]. The mine transient electromagnetic method is affected by the volume effect, has a low resolution, has difficulties in accurately identifying practical geoelectric interfaces, and is generally used to detect the stratum water abundance [17,18]. (4) In-seam electrical resistivity imaging methods: Given that detection results in different directions are closely related to the electric characteristics of mediums adjacent to the electrodes, an all-round prospecting can be conducted on concealed geological structures in coal measure strata [19,20,21]

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