Abstract: According to geological material, analysis of geological features of great thick coal seam massive fully-mechanized top-coal caving mining under the Jing River in Xiagou coal mine, in order to achieve mining safety under the water, it is determined the mining plan that remained the isolated pillar with a definite width between the work faces. By similar material tests, analysis of the isolated pillar with a definite width to have an effect on overlying strata failure under geological conditions in the area; the achieved results prove that the isolated pillar can effectively control overlying strata failure. The test results provide the largest ratio of fissure zone height and mining thickness of single work face, and by the least vertical height calculating of the safe coal post preventing water, hold that geological conditions meet the requirements of the safe stoping. Research results successfully guided the safety stoping of the five work face; it will provide references to those mines with similar conditions in Xiagou mine area.

Key words: oal mining under the river, fully-mechanized top-coal caving mining, isolated pillar, similar material model test, overlying strata failure, water conducted fissure zone