The effect of rock mass gradual deterioration on the mechanism of post-mining subsidence over shallow abandoned coal mines

•Post-mining subsidence is a challenging problem in rock engineering.•The modified Tributary Area Method (TAM) was used to estimate the lifetime of pillars.•The effects of gradual deterioration was incorporated in the numerical modelling.•The long-term stability of an abandoned room and pillar coal mine was investigated.•This study showed that deterioration plays a significant role in the long-term stability of mining excavations.

In this study, the effect of gradual deterioration on the long-term stability of shallow abandoned room and pillar coal mines is investigated. The conventional Tributary Area Method is adopted and modified to take into account the rate of deterioration on the lifetime of pillars. Moreover, a simple quantitative approach is proposed to incorporate the effects of deterioration in numerical modelling. The suggested methods are then used to assess the stability of the shallow abandoned room and pillar coal mines around Dolphingstone village, UK. Results of this study indicate that the gradual deterioration plays a significant role in the long-term stability of shallow abandoned coal mines. The stand-up time of a room and pillar mining panel is also estimated based on the modified Q-system. A good agreement is observed between the results of numerical modelling and the rock mass classification system.