Mechanism of instability of section coal pillar in steeply dipping seam based on large-scale strata control technology

In order to achieve the technology for a large-scale ground control between sections and improve the stability of steeply dipping seam longwall face “ Roof-Support-Floor” system,based on the analysis on the section of gob sur-rounding rock instability mechanism, this paper established an inter section rock instability model, researched the stress distribution law and instability criterion of the section coal pillar,and determined the rea-sonable size of the sec-tion coal pillar. The results show that the steeply dipping seam section of surrounding rock movement can be summa-rized as two modes of “extrusion-bend down” and “crush-dumping”. In order to realize this technology,the surround-ing rock of the gob will lose stability in a “crush-dumping” mode. When the overburden structure exists in the form of “ beam arch combined beam”,the strength of the section coal pillar determines the movement mode of the surrounding rock in the gob section. When the overburden structure is in the form of “ double arch continuous beam”,the size of section pillar determines the pressure behavior characteristics of the “crush-dumping” mode and the gob’ s three-di-mensional spatial form after the deformation and failure. Thus the key of this technology lies in the design of the section coal pillar. According to the strength and instability criterion of the section coal pillar,it is determined that the width of k must satisfy the k>kZH condition and meet the k>kSK condition as much as possible. In a case study at the multi-sec-tion mining of steeply dipping seam in Gansu DONGXIA coal mine,the comparative analysis of the theoretical calcula-tion and similar simulation experiment was carried out,and the mechanism of the pillar instability was verified.