Steindler, A, Leventhal, A, Hull, T, Matheson, J & Sheppard, I 2015, 'Geotechnical monitoring of railway infrastructure subject to mine subsidence-induced horizontal closure', in PM Dight (ed.), FMGM 2015: Proceedings of the Ninth Symposium on Field Measurements in Geomechanics, Australian Centre for Geomechanics, Perth, pp. 565-580, https://doi.org/10.36487/ACG_rep/1508_39_Leventhal (https://papers.acg.uwa.edu.au/p/1508_39_Leventhal/) Abstract: Surface subsidence produced by longwall mining beneath mainline railways produces numerous technical challenges for the engineering profession, covering inter alia mine subsidence prediction, civil engineering management of the track, electronic remote monitoring of the rail, and management of rail infrastructure — all in the context of maintaining rail safety combined with efficient resource recovery. This is worldleading practice. Near Tahmoor, NSW, longwall mining is being undertaken at a depth of cover of 440 m and subsidence of the Main Southern Railway of up to 0.9 m has occurred during multi-pass longwall panel retreats. This paper presents details of the monitoring of structural and geotechnically-based intervention measures to manage track safety without impeding mining operations. The methodology is illustrated by way of a case-history which deals with a structure that is a 100-year-old, inverted horseshoe shape, under-track, brick arch culvert of 4.5 m diameter, with shallow cover to the underside of the rail formation. The paper discusses the monitoring philosophy, measurement protocols, checks and balances, calibrations, and result interpretations. A particular challenge that will be addressed in the paper is discrimination of seasonal and diurnal effects from the mining-induced creek closure effects.