Geophysical characterization of derelict coalmine workings and mineshaft detection: a case study from Shrewsbury, United Kingdom

Abstract

A study site of derelict coalmine workings near Shrewsbury, United Kingdom was the focus for multi-phase, near-surface geophysical investigations. Investigation objectives were: 1) site characterization for remaining relict infrastructure foundations, 2) locate an abandoned coalmine shaft, 3) determine if the shaft was open, filled or partially filled and 4) determine if the shaft was capped (and if possible characterize the capping material).Phase one included a desktop study and 3D microgravity modelling of the relict coalmine shaft thought to be on site. In phase two, electrical and electromagnetic surveys to determine site resistivity and conductivity were acquired together with fluxgate gradiometry and an initial microgravity survey. Phase three targeted the phase two geophysical anomalies and acquired high-resolution self potential and ground penetrating radar datasets. The phased-survey approach minimised site activity and survey costs.Geophysical results were compared and interpreted to characterize the site, the microgravity models were used to validate interpretations. Relict buildings, railway track remains with associated gravel and a partially filled coalmine shaft were located. Microgravity proved optimal to locate the mineshaft with radar profiles showing 'side-swipe' effects from the mineshaft that did not directly underlie survey lines.Geophysical interpretations were then verified with subsequent geotechnical intrusive investigations. Comparisons of historical map records with intrusive geotechnical site investigations show care must be taken using map data alone, as the latter mineshaft locations was found to be inaccurate.

Void detection beneath reinforced concrete sections: The practical application of ground-penetrating radar and ultrasonic techniques

“…Such features are common in areas of karst or evaporite dissolution and shallow mining (Pringle et al, 2008;Styles et al, 2005) and the problem is of significant concern to many areas of industrialised Europe, often as a consequence of goafing or mine roof failure.…”

Geophysical and intrusive site investigations to detect an abandoned coal‐mine access shaft, Apedale, Staffordshire, UK

“…; Pringle et al . ). The detection of small distributed voids and low‐density ground has also been recently proven to be possible using near‐surface geophysics (Tuckwell et al .…”

“…; Pringle et al . ). GPR targets can be detected either directly by observing anomalies below survey lines or indirectly due to object ‘sideswipe’ effects on nearby data sets (see Pringle et al .…”

“…Micro‐gravity surveys have also been employed to locate and characterize near‐surface voids and even low density ground (see Branston and Styles ; Pringle et al . ; Tuckwell et al . ).…”

Long-term time-lapse microgravity and geotechnical monitoring of relict salt mines, Marston, Cheshire, U. K.

“…Noninvasive near-surface geophysical methods have successfully detected and characterized near-surface voids, relict mineshafts, and low-density ground for geotechnical investigators to then target and remediate (e.g., McCann et al, 1987;Bishop et al, 1997;Wilkinson et al, 2005;Pringle et al, 2008;Tuckwell et al, 2008;Banham and Pringle, 2011;Orfanos and Apostolopoulos, 2011).…”