Risk Assessment System Based on Fuzzy Composite Evaluation and a Backpropagation Neural Network for a Shield Tunnel Crossing under a River

Table 8

Criteria for risk levels.

Risk values	0–40%	40–70%	70–85%	85% or more
Risk level	Low	Medium	High	Very high
Treatment	No risk treatment measures or monitoring required	Enhanced monitoring, but no need for risk treatment measures	Risk management measures and enhanced monitoring	Highly focused and avoidant, mitigating risk at all costs