Optimization of parameters of excavation support and down-section blasting in limestone ore pass

NIU Shuai; LIU Shaowei; FAN Kesong; LI Xiaopeng; GUO Zezheng

doi:10.16186/j.cnki.1673-9787.2023060044

Abstract：The method of"ore storage down-section"is a technique in which the down-section extends with the progression of open-pit mining.Objectives The stability of the chute's shaft wall is a crucial aspect during the down-section process,but the internal state of the chute is invisible.Therefore,it is particularly impor-tant to study the appropriate support mode for the wellhead before down-section blasting and to optimize the blasting parameters for stability during the down-section process.Methods Based on a limestone mine chute,a theoretical analysis was conducted to assess the impact on chute wall stability.The stability of the chute wall was studied before and during the blasting down-section.Numerical simulations were employed to investigate the stability of the chute wall under different support conditions after excavation and through mul-tiple blasting events.Results The findings revealed that the impact degree of disturbances caused by blast-ing on the wellhead and shaft wall was negatively correlated with the distance between the shaft and the blasting center.The stress distribution and failure patterns of the chute wall after excavation and during the blasting down-section were identified,leading to the determination of a more reasonable wellhead support method.Conclusions Supporting the shaft head of the limestone mine with C40 grade concrete could effec-tively mitigate the damage to the surrounding rock caused by vibrations from daily blasting.The optimal pa-rameters identified included a resistance distance of 3.5 m for the auxiliary hole chassis,a hole distance of 3.5 m,and a row distance of 3.5 m.These findings offered a theoretical foundation and reference value for enhancing the safety of the blasting down-section process.