The Coal Pillar Width Effect of Principal Stress Deflection and Plastic Zone Form of Surrounding Rock Roadway in Deep Excavation

Figure 4

Angle cloud chart of maximum principal stress and horizontal direction of surrounding rock. (left side is coal pillar, right side is coal wall).

(a) 4 m coal pillar

(b) 6 m coal pillar

(c) 8 m coal pillar

(d) 10 m coal pillar

(e) 12 m coal pillar

(f) 14 m coal pillar

(g) 16 m coal pillar

(h) 18 m coal pillar

(i) 20 m coal pillar