Development of backfill design parameters for control of surface and subsurface mining related movements

摘要

Surface and subsurface deformations of overlying strata inevitably occur during the process of longwall mining.In order to protect water resources,agricultural lands,buildings,and railroads,partial or complete mine backfilling method is considered an effective approach.Cemented and compacted backfill is commonly practiced for ground and subsidence control in high extraction mining areas.Backfill stiffness and strength parameters must be designed to achieve desired control of rock mass deformations.Since these parameters may vary with time,both initial and final values of these parameters must be designed.A simplified ground mechanics model based on the concepts of beams on elastic foundations with varying stiffness is used here to analyze the deflection characteristics of overlying strata with cemented backfill.This model can be used to estimate the final deflections of immediate roof,maximum horizontal strains,and final surface subsidence movements.The model can also be used to estimate timevarying strength and stiffness parameters of the backfill based on the limiting maximum surface subsidence and critical horizontal strains.The model also permits estimation of deflections after the longwall face has been backfilled a certain distance.The authors present the model and the application of backfill properties for one mine in China.