Numerical Simulation on Hard and Stable Roof Control by Means of Directional Hydraulic Fracturing in Coal Mine: Fid-Bau Portal

Numerical Simulation on Hard and Stable Roof Control by Means of Directional Hydraulic Fracturing in Coal Mine

Pan, Chao / Zuo, Yu Jun / Gao, Shang / Li, Wei

Hydraulic fracturing is a method which combines a natural action with a factitious means to alter rock structure. In order to control the extending direction of fracture in the process of hydraulic fracturing, directional hydraulic fracturing is necessary. According to fracture initiation and extension mechanism, taking fully into account the flow-stress-damage coupling effect, simulating with numerical way and analyzing a law of the roof under the dynamic failure process on a working face with a hard and stable roof in 2 cases, the one is the non-directional directional hydraulic fracturing, and the other one is wedge groove directional hydraulic fracturing by RFPA^2D-Flow. Based on analyzing the distribution law of the primary stress field on roof surrounding rock, we reveal the control mechanism and behavior law of directed by wedge groove directional fracturing. The study results shows that: First, under the coupling effect from the high hydraulic pressure and crustal stress, failure of roof is not simply a shearing failure, but a compound stress effect from tensile and compress failure which tension contributes more. Second, the directional fracturing by wedge-groove guides to the main fracture progressing into directional expansion, relying on man-made weak plane, it also makes the roof directional hierarchically, timely and fractionated carving come true.