Abstract: To understand the evolution and formation of gas (methane) channels in overlying strata during mining close distance seam group, formation mechanism of crack fields in overlying strata was studied by using the method of similar simulation. The results show that mining crack field spreads non-uniformly with the face advancing, it expands faster during the weighting than normal, that the mining crack field has the relationship of synchronous coordination with the face advancing and can be divided into fractured development zone, fracture penetration zone and compacted area, and the evolution of mining crack field is exacerbate during the superposition mining in close distance seam group, the crisscrossed gas flow channels are formed and can be divided into advantage gas channel zone, transition zone of advantage gas channel and general gas channel zone, and the flow capacity of gas reduces in turn.

Key words: close distance seam group, crack field, superposition mining, advantage gas channel, gas extraction