Sensitivity analysis of overburden water-resistant strata stability based on the mechanical properties of backfill body

Abstract

Strata movement control during coal seam’s backfill mining is very much related to the mechanical properties of backfill body in goaf. A mechanical model of the structural water-resistant strata (SWRS) of stope overburden in backfill water-preserved mining (BWPM) was established on the basis of the key strata theory in ground control. This approach was conducted to investigate the mechanical properties of backfill body on the overburden water-resistant strata stability. The proposed model was based on the compressive mechanical properties of the filled gangue, which considered the linear and nonlinear elastic mechanical properties of backfill body. The stability mechanics criterion of the SWRS of stope overburden in BWPM on the nonlinear elastic foundation was deduced by introducing the tensile yield criterion. The maximum tensile stress (MTS) that acts on the SWRS of stope overburden decreased with the increase of the backfill body’s linear elastic foundation coefficient of k1 and the nonlinear elastic foundation coefficients of k2 and k3. However, the MTS rapidly decreased with the increase of k1 and slowly decreased with the increase of k2 and k3. The sensitivity analysis indicated that k1 exhibited the greatest effect on the MTS that acts on the SWRS, thereby accounting for 72.38%. In addition, k2 and k3 showed less effect on the MTS that acts on the SWRS, thereby only accounting for 19.56% and 8.06%, respectively. Results showed that the backfill body’s linear elastic foundation coefficient plays a very important role in controlling the stability of the SWRS of stope overburden in BWPM. Increasing k1 is more beneficial to the stability control of the water-resistant strata of stope overburden than increasing k2 and k3, especially the latter.