Abstract: For the possible leakage and diffusion of existing natural gas pipelines under Tianjin urban main road and the risk of inducing explosion, combined with the climatic characteristics of the city, the leakage and diffusion characteristics of natural gas pipelines at the leakage point and the impact of explosion shock waves on nearby buildings were studied based on FLACS. The results show that the influence of wind speed on the leakage and diffusion of natural gas pipeline under the main road is obvious. The larger the wind speed is, the smaller the natural gas cloud in the explosion range is, which is more favorable for emergency rescue. However, the possible changes of wind speed and wind direction during the rescue process should be fully considered, when closing the natural gas valve and evacuating people in the downwind direction, the dangerous behavior within 5 m around the leakage point and 24 m from the ground height should be strictly controlled. The leakage and diffusion of natural gas pipeline under the main road has a great impact on the surrounding area. The horizontal diffusion distance of natural gas under the maximum wind speed of the city can reach 25 m. The area should be evacuated in time. The explosion overpressure of natural gas pipeline leakage under the main road decreases with the increase of the height above the ground. The maximum overpressure exceeds 1.5 kPa,the peak value of overpressure load is mainly concentrated within the range of 4~22 m above the ground so the anti?explosion protection should be considered.

Key words: urban main road, natural gas pipeline, leakage diffusion, leakage explosion, gas explosion, FLACS