Risk Assessment of Water Inrush in Tunnels: A Case Study of a Tunnel in Guangdong Province, China

Fractured tectonic zones with developed groundwater are one of the major causes of water inrush in the construction of igneous tunnels; thus, it is highly important to assess the risk of water inrush. In this study, a total of six evaluation attributes, groundwater level, amount of inrush water, permeability coefficient, strength of the surrounding rock, rock integrity, and width of the jointed and fault fracture zone, were selected for the risk assessment of water inrush, and fuzzy theory was applied to the treatment of the uncertainty in the evaluation attributes. On this basis, the MULTIMOORA (multiple multi-objective optimization by ration analysis) and the model of nearness degree of incidence were combined to obtain the new model of MULTIMOORA-nearness degree of incidence for the risk assessment of water inrush. A deep-underground, extra-long tunnel under construction in southern China was used as an example for validation. The six tunnel sections assessed on site were ZK91 + 195 similar to 236, K91 + 169 similar to 186.5, K91 + 203 similar to 238, ZK94 + 238 similar to 198, K94 + 112 similar to 82, and K94 + 076 similar to 034. K94 + 112 similar to 82 was assessed at risk Level III, while the remainder were assessed at risk Level IV. The site conditions were also Level III for section K94 + 112 similar to 82 and Level IV for the remainder. The assessment results for the above six tunnel sections are consistent with the field conditions, which verified the validity of the model of the MULTIMOORA-nearness degree of incidence.