Cause analysis on coal and gas outburst in low index with K1 value of tectonic coal developed area

This paper focuses on revealing the technical reason of the phenomenon that coal and gas outburst occurred frequently in low index with K1 value in tectonic coal developed area.Drilling cutting gas desorption index K1 of the working face was tracked and tested using laboratory tests on coal samples of both tectonic coal and original coal.It is found that the drilling cutting gas desorption index (K1) of the tectonic coal is significantly higher than that of the original coal under the same adsorption equilibrium pressure.The value of K1 is proportional to the development degree of the tectonic coal.The initial characteristics of gas emission in tectonic coal were also studied using constant temperature gas emission experiments.Based on the test results,the technical reasons for the deviation of the K1 measurement were analyzed.The results show that the Barriar formula has limitations in calculating K1.The drill cuttings mixing of different drilling depths and different structural types is an important reason that cause deviation of K1 from the actual value.The longer coal sample exposure time is associated with greater deviation between the tested K1 value and the actual value.This research will provide technical support for the improvement of coal and gas outburst prediction technology.