Abstract: In response to the problem of more influence factors and difficulties in identifying the depth of damage floor of coal seam, six factors including mining depth, mining height, incline section length (working face), dip angle, floor lithological combination and roof lithological combination were selected to research the depth of damage floor by analyzing two aspects influential elements of the deformation degree of the floor rock, geological model was generalized and six factors and five levels orthogonal numerical simulation experiment were carried out with mine 4602 working face as the background. The experimental results showed that: (1) The main factors influencing the depth of damage floor were incline section length, floor lithological combination, roof lithological combination, mining depth and mining height were weakened in order, dip angle was weakest; (2) that roof lithological combination was the key factors in influencing the floor damage depth was made clear for the first time; (3) prediction model of mining depth of damage floor on incline section length - floor and roof lithological combination - mining depth - mining height - dip angle was established, the calculation results were more close to reality comparing with the results of mining regulation empirical formula calculation, and the precision was high, the error was low, and it can meet the engineering use basically. The results of the study had a positive guiding significance on the research of the depth of damage floor and engineering application.

Key words: depth of damage floor, numerical simulation, orthogonal test, roof lithologic combination