A meta-analysis of coal mining induced subsidence data and implications for their use in the carbon industry

Many empricial subsidence estimation tools exist worldwide but are designed and calibrated for specific coalfields. This paper presents an universal tool for the estimation of maximum subsidence (S-max). The subsidence tool is based on pooling and meta-analysis of empirical data from a number of different countries and coalfields. The key factors influencing S-max are the void dimensions and the mechanical competency of the overburden. These factors are used to estimate subsidence using the empirical equation S-max = [c/(1 + 10 boolean AND(-a((W/ D) - b)))] *m, where W is the width of the void, D the depth, m the effective void thickness, and a, b, c are parameters related to the mechanical competency of the overburden. This universial empirical method was validated against historical data from United Kingdom and Australia. The method also provided S-max estimations for underground coal gasification (UCG) projects, that were inline with those from numerical modelling under certain conditions. This tool would likely be most useful when investigating areas, where there are little or no historical data of subsidence and mining. Such areas are most likely to be targeted by UCG schemes.