Table 5 Roof fall and rib spalling accident risk point.
Inherent risk | Quantitative indicators | Characteristic indicators | Quantitative value | |
|---|---|---|---|---|
hs | Roof rock mass quality index | Rock mass basic quality (BQ) | 550 ≤ BQ | 1 + 0.175n |
451 ≤ BQ < 550 | ||||
351 ≤ BQ < 450 | ||||
251 ≤ BQ < 350 | ||||
BQ ≤ 250 | ||||
E | Exposure risk index of operators in unstable roof roadway and goaf | Number of people exposed at risk point (P) | 100 ≤ P | 9 |
30 < P ≤ 99 | 7 | |||
10 < P ≤ 29 | 5 | |||
3 < P ≤ 9 | 3 | |||
0 ≤ P ≤ 2 | 1 | |||
M | Degree of goaf treatment | Complete treatment | 1 | |
local treatment | 6.3 | |||
untreated | 9 | |||
Continuous goaf volume > 1 × 106m3 | 9 | |||
K1 | Roof subsidence monitoring | Monitoring and control facilities failure rate l | 1 + l | |
Surface subsidence monitoring | ||||
K2 | Number of high-risk types of operations involved in powered haulage system | Safety inspection operation | 1 + 0.05t | |
Pillar operation | ||||
blasting operation | ||||
