A Risk Assessment of a Water-Sand Inrush during Coal Mining under a Loose Aquifer Based on a Factor Analysis and the Fisher Model

Abstract

This paper aims to investigate the safety problems related to coal mining under a loose aquifer, and uses the Factor Analysis (FA) and Fisher discriminant methods to analyze and assess the risk of a water-sand inrush under such conditions. Based on 26 sets of the collected geological parameters of the working faces of coal mines under loose aquifers, a comprehensive analysis shows that the risk factors of a water-sand inrush under a loose aquifer are mainly: the thickness of the bottom aquifer; the water pressure; the height of the caving zone; the thickness of the bedrock; the thickness of the bottom clay layer; the water abundance of the aquifer; and the water inflow at the working face. These factors were used as discrimination factors to test and predict the results by using the back-substitution estimate method. The results show that: the water pressure and the thickness of the bottom clay layer have a major influence on the risk of a water-sand inrush under a loose aquifer; and the predicted results of 23 sets of samples are consistent with the results from actual engineering practice, while the results of the remaining three sets are inaccurate. Accordingly, the error rate of the model is 0.115. Therefore, the FA-Fisher discriminant analysis model is highly reliable when conducting a risk assessment of a water-sand inrush under a loose aquifer, and can provide a scientific reference for the safety evaluation of coal mining under such conditions.