1 and No. 2 form a trap to the methane libra-ted from No. 1 seam and its overlying zone contained free methane.

• 1号煤和2号煤之间先垮落的岩层对1号煤及其瓦斯飘逸带垮落后释放的瓦斯有一定的阻滞作用。