A Research On Fire Smoke Control And Evacuation In Highway Tunnel Based On Multi-layer Zone (MLZ) Model

With the development of national tunnel construction technology, growing large/long highway tunnels are being constructed, which can support much higher speed and larger traffic volume. Fires in tunnels with rapidly-spreading high-temperature toxic gas put serious threats to the safety of life and property.Based on the reasons, the analysis of many tunnel fire cases at home and abroad showed (that) about 70% of tunnel fires resulted from burning vehicles or goods caused by vehicle collision or electric leakage. Then, Multiple Layers Zone model (MLZ) was used to study the law of smoke diffusion in tunnel. The MLZ mathematical model was established based on the study on the combustion source model, plume model and smoke flow (horizontally and vertically) calculation model, and programmed based on the MATLAB language. Last, the smoke control effects under various ventilation operation and the evacuation strategy of twin clogging phenomena are caculated and analyzed, providing a reference for personnel evacuation and fire emergency service.The conclusions are as follows:(1) The critical wind velocity (CWV) of tunnel fire and the highest temperature of gas in tunnel vault by MLZ calculation program arrived at a conclusion that the CWV increased with the fire power (FP) in logarithmic curve rule; the highest temperature of gas in tunnel vault decayed more faster with a wind speed of 2m/s-3m/s in fires with FP 20 MW and 30 MW. (2)The longitudinal ventilation designed for a 20 MW fire could meet the requirement of personnel evacuation for a 30 MW fire.(3) Simulated evacuation results showed that for longitudinal ventilation tunnels, the longitudinal wind velocity in the upstream side of a fire was necessarily improved in one-way tunnels and the longitudinal induced wind velocity should be less than the personnel walking speed in two-way tunnels. (4) For semi-transverse ventilation tunnels, when a fire occurs in the middle of a tunnel, the remote smoke vents should be closed to improve exhausting smoke ability around the combustion source, controlling the dangerous area (with high temperature gas) within about 30 m; and if a fire occurs within one shaft of a twin shafts controlled tunnel, ventilation should be operated in the other shaft. (5)It’s needed to reasonably control the longitudinal ventilation value for longitudinal-transverse composite ventilation system, so that the longitudinal ventilation velocity less than CWV.