Research Article

Intelligent Early Warning System for Construction Safety of Excavations Adjacent to Existing Metro Tunnels

Table 2

Security risk classification and alarm signal selection.

Risk levelTotal deformation/thresholdRisk alarm signalSignal color

Low level (I)Risk ignoredBlue
Moderate level (II)Risk concernedGreen
High level (III)Risk controlledYellow
Extreme level (IV)Risk preventedRed

 = deformation amount/threshold.