Intelligent Autofeedback and Safety Early-Warning for Underground Cavern Engineering during Construction Based on BP Neural Network and FEM

Table 4

The results of safety early-warning.

	Pairs of characteristic points	Convergence deformation; (cm)	Allowable deformation; (cm)	Safety early-warning
Powerhouse cavern	Arch center; Bottom center	8.0	7.8	Support is needed
	Left arch foot; Right arch foot	2.6	15.9	Safe
Transformer cavern	Arch center; Bottom center	10.1	8.6	Support is needed
	Left arch foot; Right arch foot	1.2	12.2	Safe