Shield-Roof Interaction in Longwall Panels: Insights from Field Data and Their Application to Ground Control

Figure 17

Yield valve malfunctions. (a) Frequency distribution of close and open pressure of yield valve. The setting yield pressure is 41 MPa. (b) Frequency distribution of open and close duration of yield valve. (c) Frequency distribution of leg closure during yield open and close. (d) Frequency distribution of pressure increment/drop during yield open and close.

(a)

(b)

(c)

(d)