Experimental study on the evaluation of coal burst tendency utilizing modulus index

In order to study the feasibility of evaluating the bursting tendency of coal by modulus index,the modulus index,bursting tendency evaluation indexes and acoustic emission signal of four group coal specimens with different bursting tendency strengths are determined. The correlation between the modulus index and the other evaluation inde- xes of the bursting tendency and the valuation results of bursting tendency are analyzed. The influence of the modulus index on the internal energy release characteristics of coal is analyzed according to acoustic emission signal. The results show that the modulus index is related to other evaluation indexes of the bursting tendency. The correlation between co- axial compressive strength is the strongest. For the coal specimens with the same bursting tendency,the change range of modulus index of each specimen is small. For the coal specimens with the different bursting tendency,the change range of modulus index of each specimen is large. The magnitude of modulus index of coal is related to the bursting tendency of coal. The stronger the coal bursting tendency is,the larger the modulus index is. The results of evaluating the coal bursting tendency according to the modulus index are consistent with the evaluation results of other evaluation indexes. The softening modulus of different bursting tendency is the key factor to determine the modulus index of coal, and the influence of elastic modulus on modulus index can be ignored. The release characteristic of internal energy of coal specimens is related to the magnitude of modulus index. The acoustic emission events occur frequently during the whole loading process of coal with large modulus index,while acoustic emission events releasing high-energy centrally occur in the coal with small modulus index at the peak load moment. The modulus index can be used to evaluate the coal bursting tendency,and the influence of modulus index on coal energy release can be used to guide on-site monito- ring.