Table 2.

Vertical stiffness of the shield at a particular operating height

Shield typeMin. operating height (m)Operating height (m)Extension of hydraulic liquid* (m)Shield stiffness (t·mm−1)Vertical compression of coal upon onset of yield (mm)Developed load upon face yielding (t)
ZY10800/28/63D2.85.83.016.85.8 × 103 × 0.5% = 29487.2
ZY15000/33/723.36.33.026.26.3 × 103 × 0.5% = 31.5825.3
ZY18800/32.5/72D3.256.83.5522.26.8 × 103 × 0.5% = 34754.8
ZY26000/40/88D4.08.54.525.18.5 × 103 × 0.5% = 42.51066.75
• * Extension of hydraulic liquid is computed as active operating height minus minimum operating height.

• Developed load inside the leg cylinder upon face yielding is calculated as shield stiffness by vertical compression of coal upon onset of yield.