A Simplified Ground Mechanics Model of Longwall Mining with Cemented Backfilling

摘要

The movement of overlying strata and surface subsidence occur due to longwall coal mining.Characterization and control of such movements is considered critical in China because of land development,protection of agricultural lands and water resources.Cemented and un-cemented backfill is typically used to control the rock mass movements.Rock mass movements are a dynamic process with the change of time and space,and the process becomes more complicated with use of cemented backfilling technology.In order to describe the characteristics of deflection of overlying strata under the condition of cemented backfilling,mathematical and mechanical models based on concepts of beams on elastic foundations may be used.Using these concepts and finite difference methods for numerical modeling,characteristics of displacement and deformation of rock strata overlying the coal seam under caving conditions were developed first.The numerical model was then extended to include cemented backfill whose mechanical properties vary with time as it gains strength and stiffness.This permitted realistic analysis of rock movements above the coal seam with and without backfilling.The model also permits estimation of time-dependent backfill characteristics to achieve desired surface and sub-surface rock mass movements.The model was also validated using two-dimensional finite element analyses.