Sensitivity analysis of factors influencing pillar stability in the deep stope of underground salt mine

Abstract

The orebody and the surrounding rock of underground salt mine are generally divided into soft rock or extremely soft rock. In these mines, the strip room pillar method is primarily used. Continuous pillars with a certain width are left between every two mining strips. These pillars are used to provide support to the overlying surrounding rock. However, the stability of the pillars restricts the stope structural parameters of the mining method. Thus, it is important to first determine the main factors that affect pillar stability and analyze the influence level of these factors. Using a deep mining underground salt mine as an example, the characteristics of pillar instability and the pillar load are analyzed. The safety factor of the pillar refers to the ratio of pillar strength to pillar load, which can be used to quantitatively evaluate pillar stability. Based on the formula of pillar stress and the empirical formula of pillar strength, the formula of the pillar safety factor is deduced. Based on this formula, the primary factors affecting pillar stability are comprehensively analyzed. Moreover, the sensitivities of these factors are compared and analyzed based on the orthogonal range theory. According to the calculation results of the range, the factors influencing pillar stability in the underground salt mine are the mining depth and uniaxial compressive strength of ore, which are the most significant factors, followed by the height and width of pillars, and then the room width and unit weight of the overlying strata, which have relatively small influence. The safety factor of the pillar is positively correlated with the pillar width and uniaxial compressive strength but negatively correlated with the mining depth, pillar height, room width, and the unit weight of the overlying strata. The specific reasons of each factor affecting the safety coefficient are analyzed in detail. The changing trend of the pillar safety factor with various influencing factors can provide an important basis for the optimal design of stope structural parameters and the determination of support scheme.