Experimental Study on Crack Extension Rules of Hydraulic Fracturing Based on Simulated Coal Seam Roof and Floor

Figure 12

Fracture propagation graphs produced under the condition of different maximum and minimum horizontal principal stress ratios.

(a) Maximum and minimum horizontal principal stress ratios: 0.35

(b) Maximum and minimum horizontal principal stress ratios: 0.47

(c) Maximum and minimum horizontal principal stress ratios: 0.65

(d) Expansion angle change