Directionality of butterfly leaves and nonuniform deformation mechanism in gob-side entry driving roadway

ABSTRACT

Existing rock pressure theory, with the pressure-plastic zone as the core, cannot reveal the nonuniform large deformation mechanism of the surrounding rock in a deep roadway. To address this problem, the 11030 gob-side entry driving roadway of the Zhaogu No. 2 Mine is used as an example, in conjunction with elastoplastic mechanics theoretical analysis, to study the butterfly plastic region and the direction of the butterfly leaf in the homogeneous circular roadway. In addition, the finite-element method was used to study the environmental characteristics of the stress field of the surrounding rock before the excavation of the gob-side entry driving roadway and to analyze the effect of the principal stress on the butterfly plastic region of the surrounding rock. The results showed that, under the combined action of high ground stress and disturbed stress, the surrounding rock of the deep front edge of the gob in the central area of the main stress could form a large range for the butterfly leaf plastic area. The deflection angle of the four butterfly leaves in the plastic region was the same as that of the main stress direction. The butterfly plate plastic zone that formed in the deep surrounding rock of the gob-side entry driving roadway led to not only extension, degradation and disappearance to different degrees, but also deflection under the action of the main stress. This led to large deformation of the rock strata in the butterfly leaf plastic region, ultimately causing uneven deformation and failure of the 11030 roadway.