Review of Horizontal Surface Movements Due to Longwall Coal Mining Using Numerical Modelling

Strain is an important parameter for assessing the potential for impacts on surface features due to longwall mine subsidence, but it is also one of the most difficult parameters to predict. Whilst profiles of strain can be highly variable and irregular, zones of net compression and net tension generally develop above longwalls. By considering the relative horizontal surface movements over longer bay lengths, they become more regular and, hence, more predictable. Numerical modelling has been undertaken using universal distinct element code (udec) to assist with the development of predictive methods for the relative horizontal movements over the various zones above an active longwall. The numerical modelling was used to assess the effects of varying surface topography on the horizontal movements, including slopes, scarps, hills and small valleys. Predictive equations have been developed for the net compression within the sagging curvature zone and the net openings within the hogging curvature zones. These equations are consistent with the findings from reviews of ground monitoring data in nsw coalfields