Risk assessment of water inrush in karst tunnels and software development

Water inrush makes time extended, instruments destructed, and casualty increased, which is the biggest threat for safe construction of tunnels in karst areas. A software system for risk assessment of water inrush was established with considering eight risk factors, including groundwater level, unfavorable geology, formation lithology, topography, strata inclination, excavation, advanced geological prediction, and monitoring. In the present software system, fuzzy mathematics and Analytical Hierarchy Process (AHP) were used to quantitatively describe the risk levels for each factor. The influence degree of each factor to water inrush was assigned an objective weight and a subjective weight, and the proportion of the two weights in the risk assessment was defined as weight distribution. The objective weights of the risk factors were obtained from more than 100 water inrush instances in karst tunnels, whereas the weight distribution was totally derived from expert field assessment and subjective weights were determined by using AHP in the risk assessment. Two case studies of karst tunnels were applied to check the reliability of the proposed software system, and the comparisons between the software assessment and practical excavation yield good consistency. Therefore, the software system can appropriately be used in practice to forecast water inrush in karst tunnels.