Study on Stability Prediction of Pillars Based on Bieniawski Pillar Strength Formula: a Case of a Phosphate Mine

In order to obtain the stability of pillars in Daqiao Phosphate Mine, the stability of pillars in goaf was studied by theoretical calculation. Based on the results of investigation and the calculation formula of pillar strength, a mathematical formula for calculating pillar stability was established to predict the stability of uninvestigated pillars. The effect of various factors on the stability of the pillar was analyzed by orthogonal test. The research results show that the pillar area, rock column area, and mining depth have the most significant effect on pillar stability. A mathematical formula for predicting pillar stability is constructed by means of dimensional grading method. The critical value of pillar factor is 0.06 in Daqiao Phosphate Mine. When the pillar factor is greater than 0.06, the pillar is stable. When the pillar factor is less than 0.06, the pillar is unstable. The reliability of theoretical calculation method of pillar factor is verified by numerical simulation. A mathematical formula for predicting the stability of pillars is proposed, which can be used as a reference for the stability analysis of goafs in similar mines.