Multiphase Assessment of Post-Mining Effect on Railway Structures: A Case Study of Jharia Coalfield

Subsidence-associated damage to surface structures like railway tracks over old mine workings instigate catastrophic impacts on human lives. The complexity of investigating old mine workings pose challenges owing to unapproachability restricting visual access, incomplete historical plans, limited record information, etc. The crux in studying unapproachable areas circumscribes the ambit of in-depth research. Thus, the framework of the investigational approach has been addressed in three segments (subsidence investigation, geophysical investigation and coal pillar stability analysis) to gather additional records to culminate the safety of the railway track located above old workings. A subsidence investigation has been conducted for a period of 9 months to assess the present status of ground movement along the railway track. Integration of geophysical investigation led to evaluating the impact of old workings on the overlying strata that can lead to subsidence in the future. Electrical resistivity tomography (ERT) technique has been used to assess the status of old underground workings, which resulted in the identification of sub-surface void as well as overlying strata disturbance status. Numerical modeling using FLAC3D, including the empirical method, has been undertaken to investigate the stability of coal pillars with respect to pillar dimensions and rock properties. The multiphase investigation resulted in arriving at a concrete understanding of the ground condition with respect to stability.