Abstract: Soft roof and floor of coal seam could be easily damaged while support was not timely and strength was not enough, so overall support was needed for laneway with strong support strength. Took drift of S1136 section of a mine in Sichuan province as the research object, through site observation results and data fitting, the relationship curve distribution presented "S" shape was obtained between roof squat and time, and common relationship expression was established according to different changing speed. The common curve of roof squat and time relationship was divided into four stages: primary development stage, constant velocity stage, development velocity attenuation stage and steady stage. The result of curve shape were obtained related to roof rock formation property, support mode, laneway buried depth, driving effect degree and other factors. In addition, curve would lack of primary development stage influenced by different roof strata property and different driving effect degree.

Key words: Time function, Soft broken roof, Deformation rule, Layout of station, "S", shaped curve