Study on Dynamic Evolution of Roof Crack and Support Timing of Secondary Tunneling for Large Section Open-Off Cut in Deep Mines

<div>The development process of roof cracks in the full section and failure mode of roof: (a) Stage I; (b) Stage II; (c) Stage III; (d) dynamic evolution of roof crack after second excavation. (The green cracks represent tensile cracks, and the red cracks represent shear cracks.)</div>

Advances in Civil Engineering

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Figure 6

Figure 6: Study on Dynamic Evolution of Roof Crack and Support Timing of Secondary Tunneling for Large Section Open-Off Cut in Deep Mines 