Reasonable protective coal pillar retention and control for working faces in the footwall of a normal fault

LIU Xiaoming; SHI Guangjin; WANG Zhiqian; FAN Deyuan; MENG Xingguo; WANG Lun; PEI Hongxi

doi:10.11799/ce202602008

Abstract：The haulage roadway of 232206 working face in Meihuajing Coal Mine was near a fault.Under the combined effects of mining-induced stress and fault tectonic stress,the roadway was prone to deformation and failure,with surrounding rock deformation exhibiting significant differences across various stages.To address this issue,UDEC numerical simulation was first employed to investigate the reasonable width of the fault protective coal pillar,revealing the characteristics and patterns of fault activation under different coal pillar widths.When the fault protective coal pillar width is less than 50 m,mining of 232206 working face induces fault activation.As the coal pillar width decreases,the vertical displacement near the fault gradually increases while its range decreases,indicating that the fault activation becomes more pronounced and occurs at a lower position.Compared with a 30 m fault protective coal pillar,the vertical stress at the fault zone is reduced by 34.5%when a 60 m pillar is retained.Subsequently,the cusp catastrophe theory was applied to reveal the relationship between the plastic zone of the fault protective coal pillar and its width.It was found that the reasonable fault protective coal pillar size is achieved when the ratio of pillar width to the unilateral yield zone width reaches 1.5.Based on field data,the calculated reasonable fault protective coal pillar width is 51.66 m.Finally,based on the investigation of roadway deformation patterns under different fault coal pillar widths,a control technical scheme for the haulage roadway of 232206 working face was designed using the pressure-relief and support synergy concept.A controlled experiment was conducted to verify the control technology.Monitoring data from measuring points in both the test section and the control section show that the surrounding rock deformation control effect is remarkable,with an average deformation reduction of 58.55%.