Experimental study on measuring coal body stress by drillpipe multiple index method

In order to accurately predict the rock burst in mines, the risk of rockburst is judged by the combination of drill pipe thrust, drill pipe rotation speed and dynamic drilling cuttings. Through the mechanical analysis of the rock cutting model and the drill rod in the drilling process of the new drilling rig, the dynamic model of drill and drill rod and the mechanical model of coal and rock are established, and the relationship among thrust of drill rod, the speed of drill rod, the dynamic drilling chip and the stress of coal body is obtained. The feasibility of measuring the stress of coal body by drilling rod thrust, drill rod speed and dynamic drilling chip is analyzed theoretically, and the method of predicting the danger of rockburst through drilling rod thrust, drilling rod speed and dynamic drilling chip volume is put forward. The thrust and speed data acquisition system is used to test the change rule of drill pipe thrust and drill pipe rotation speed under different coal stress.The experimental results show that: with the increase of drilling depth, the drill rod thrust and the speed data curve of the drill rod first increase first and then decrease steadily, but the time period of the speed stability is longer compared to the two. Under the same parameters, drill pipe thrust and drill speed have a linear decreasing relationship with coal body stress, and dynamic drilling cuttings quantity has a linear increasing relationship with coal body stress.When multiple indicators are jointly predicted, the greater the drill pipe speed is, the greater the drill pipe thrust is. On the contrary, the smaller the drill pipe thrust is, the better the consistency between the two is. The research results provide a reference for prediction and research of rockburst in coal mines.