Optimal Design Of Evacuation Exits For Underwater Road Tunnels

With the gradual improvement of the national traffic network system,the number and mileage of road tunnel construction have increased rapidly,and fire has become an important factor endangering tunnel safety in tunnel disasters.Underwater road tunnels have long length,large traffic flow,and both underwater and underground engineering properties,which are limited by structural strength and underwater geological conditions,and usually lack of pedestrian and vehicular crossings for the safe evacuation of personnel.Once a fire occurs,the safety of people’s lives and property will be greatly threatened,so the layout scheme of evacuation passageway must be considered in the tunnel design stage.The existing evacuation route layout scheme is mainly based on tunnel fire and personnel evacuation.At present,physical experiments and numerical simulation are mainly used to simulate fire and escape scenarios at home and abroad.However,physical experiments are costly and difficult to implement,numerical simulation modeling is difficult,and computing resources and time costs are high.And the layout of tunnel evacuation passageway is generally only for specific tunnels,and there is still a lack of general research on the layout of a certain type of tunnel evacuation exits.In view of this,this paper uses PyroSim software and Pathfinder software to simulate underwater tunnel fire and evacuation respectively,and analyzes the correlation rules of tunnel diameter,ventilation wind speed and fire size on available safe evacuation time(T_A),and the correlation rules of evacuation number,evacuation exits spacing and evacuation exits width on required safe evacuation time(T_R)respectively.The Bayesian and response surface-based surrogate models for T_A and T_R were developed,and the models were solved by random sampling using Markov Chain Monte Carlo(MCMC)method.The CVRMSE index of root mean square error coefficient of variation of T_A surrogate model test set was 3.23%,and that of T_R surrogate model test set was 4.13%,which shows that the two models have good prediction performance and generalization performance.The T_A and T_R surrogate models were further used to optimize the design of the evacuation exits of the underwater tunnel in A and B of Macau New Town,and it was suggested that the evacuation exits of this tunnel should be arranged with small spacing and small width,the width of the evacuation exits were 90 cm and the spacing of the evacuation exits were 104.6 m.This study provides method support and theoretical reference for the optimal design of evacuation exits in underwater tunnels.