Method for dewatering coal mine goaf by crossing neighboring goaf

A dewatering method of a device for dewatering a coal mine goaf by crossing a neighboring goaf, comprising the following steps:

• S1:
• calculating a critical hydraulic connection value l between neighboring goafs according to an equation;
• S2:
• preparing a drilling site;
• S3:
• determining that, if a thickness of a coal pillar is less than the critical hydraulic connection value 1 between the neighboring goafs calculated in step S1, a second goaf and a third goaf are hydraulically communicated with each other, and only drilling a first directional hole;
• and determining that, if the thickness of the coal pillar is greater than the critical hydraulic connection value 1 between the neighboring goafs calculated in step S1, goaf water in the second goaf is completely blocked from goaf water in the third goaf, and the second goaf is not hydraulically communicated with the third goaf due to the coal pillar, and drilling a second directional hole in addition to the first directional hole, wherein the first directional hole and the second directional hole are drilled separately;
• S4:
• inserting a water stop casing into the first directional hole drilled, cementing the water stop casing, and carrying out a pressure test on the cement of the water stop casing until a qualified pressure drop is measured over a predetermined time period or there is no leakage over the predetermined time period;
• and
• S5:
• measuring a water output from the hole after drilling is completed;
• and re-drilling in case of a decrease in the water output.