Abstract: Taking the mudstone in the coal measure strata as the research object, this thesis carries out a field test on the drilling feedback signal under different thrust level in drilling process of different compressive strength mudstone seam. The results show that：1) In test conditions, the thrust-rotational speed characteristic curves of drilling mudstone process can be obviously divided into three areas-grinding area, drilling area and blocking area. The grinding area will jump into the drilling area when the thrust reaches a certain value, but the transition zone is not obvious. 2) Drilling rate approximate increases linearly with the thrust in drilling area, which minimizes power consumption and is the optimal region for drilling rig’s working; 3) In blocking area , drilling’s growth rate does not decrease but grow negatively. The drilling rate decreases with the increasing thrust and the drilling rate dips to zero when the thrust reaches a certain level; 4) Under the same thrust, the drilling speed and the mudstone strength show an exponential relationship. With the increase of the mudstone strength, the characteristic curve of the drilling speed and the mudstone strength features show that both the drilling area and the obstructed area shift to right, the area of the thrust increases, the peak value of curve decreases and the position of the peak shifts to right and becomes flat.

Key words: mudstone, drilling and cutting district, drilling speed, feedback signals, blocking district