Pillar strength is one of the important factors for evaluating the pillar stability

which is the basis for safe mining for underground deposits. In this paper

the stress state of pillars in gently inclined layered deposits was analyzed under the combined action of normal stress and shear stress using the theory of elastic mechanics

and a generalized Mohr’s circle was plotted by graphic method to characterize the stress state of the pillars. According to the relationship between the generalized stress circle and the Mohr-Coulomb strength envelope

an analytic formula for the pillar str

ength was developed to analyze the variation of the slope of straight line（ tan

β

） at the center of Mohr circle with the dip angle of ore body. The influence of the ore-body inclination on the pillar strength was also analyzed by numerical simulation. Result shows that tan

β

is a binary function of the deposit angle θ and the lateral pressure coefficient λ. When the maximum value of tan

β

is obtained

the strength of the pillar is the smallest. When the w

p

/h

p

of the pillar keeps a same value and the ore body dip angle is within 5°～45°

the strength of the pillar gradually decreases with the increase of the dip of the ore body. The study can provide a reference for the estimation of the strength of the pillars in gently inclined bedded deposits.