Abstract: In the room-and-pillar mining of gently inclined close-distance double-layer phosphate rock,the risk of pillar
instability increases due to the influence of secondary mining,which threatens the safe production of the mine. Taking a gently
inclined double-layer phosphate rock in western Hubei as the background,the stability of the pillar under the influence of the
three factors of the dip angle of the ore layer,the thickness of the interlayer and the alignment mode of the pillar is explored.
A three-factor four-level orthogonal test scheme was designed to carry out numerical simulation of 16 working conditions. Using
the empirical formula of pillar strength considering the dip angle factor,the safety factor formula is written by fish language,and
the safety factor of each pillar in the stope under each working condition is calculated. Then,the variance analysis of the stability
factors of the upper and lower pillars is carried out to analyze the influence of the interlayer thickness and the offset rate of
the upper and lower pillars on the stability of the pillars. The results show that the safety factor of the pillars in the stope is
′asymmetric basin′,and the safety factor of the pillars in the lower stope is lower than that in the upper stope. Affected by the
dip angle,the pillars have obvious shear failure. After the thickness of the interlayer becomes larger,the mutual disturbance between
the pillars becomes smaller,and the stability of the pillars is mainly affected by the buried depth of the ore layer. With
the increase of the offset rate of the pillar,the safety factor of the pillar decreases first,then increases and then decreases. The
research provides a reference for pillar design and stability analysis of double-layer room-and-pillar mining.

Key words: double-layer phosphate deposits,dip angle of the ore layer,thickness of the interlayer,ore column,stability