Research on optimization and effect analysis of deep-hole pre-splitting blasting parameters for overlying strata during the final mining stage of fully mechanized top-coal caving under a thick coal seam with a hard roof

Zhang Xiangyang; Zhang Gaojun; Xu Linfeng; Wang Chongkai

doi:10.16186/j.cnki.1673-9787.2025040043

Abstract：Objectives To ensure the safe withdrawal of hydraulic supports during the final mining stage of a fully mechanized top-coal caving face under a thick coal seam with a hard roof,this study investigates the optimization of deep-hole pre-splitting blasting parameters and evaluates the pressure-relief effectiveness of roof cutting in the overlying strata.Methods Taking the 12314 working face in the Wangjialing mining area as the engineering background,a structural mechanics model and a numerical model of a large-space stope during the final mining stage were established.A dynamic coupling analytical method between the overlying strata load and the support bearing capacity was developed,and a stress-blocking positioning method for roof cutting and pressure relief was proposed.Results During the final mining stage,the cantilever length and height of the roof structure were identified as the dominant factors controlling support loading.Increas-ing the roof-cutting height and reducing the distance between the cutting position and the stop line signifi-cantly enhanced the stress-blocking effect.The stress-blocking efficiency gradually stabilized with increas-ing roof-cutting height,with a critical height of 35 m.In contrast,the stress-blocking effect weakened as the distance between the roof-cutting position and the stop line increased,with a critical distance of 60 m.Based on the nonlinear relationship between roof-cutting parameters and pressure-relief indicators,a predic-tion model for roof-cutting pressure-relief effectiveness was developed using surface fitting,achieving a pre-diction error of only 3.32%.Under the optimal roof-cutting parameters for the 12314 working face(roof cut-ting conducted 35 m ahead of the stop line with a cutting height of 30 m),the peak advanced support stress was reduced by 25.93%,the maximum roof subsidence decreased by 14.10%,and the peak stresses on the left and right sides were reduced by 9.83%and 5.50%,respectively.Conclusions The designed com-bination of roof-cutting parameters for the final mining stage exhibits a pronounced stress-blocking and pressure-relief effect,effectively ensuring the safe withdrawal of hydraulic support.The proposed prediction model enables rapid calculation and visualization of multiple pressure-relief indicators,facilitating the de-sign and optimization of key parameters for deep-hole pre-splitting blasting.Furthermore,the research framework of"theoretical analysis-numerical simulation-prediction analysis-on-site verification"and the stan-dardized procedure for roof-cutting parameter design provide a valuable reference for similar engineering ap-plications.