Abstract: Fluent software was used to study the process of small hole leakage in gas tank from normal ventilation to alarm response switching emergency ventilation under the conditions of longitudinal slope of 0̊, 5̊, 10̊ and 15̊ and different ventilation directions. The results show that: the diffusion direction of gas leakage is related to the slope and ventilation direction. After the accident ventilation, the diffusion direction is the same as the ventilation direction, and the diffusion speed is positively correlated with the gradient when the distance is more than 30 m from the leakage port. With the same ventilation direction, the greater the slope is, the shorter the alarm response time will be. According to the response time of the first two alarms, the location of the leakage source can be preliminarily determined under each slope. Therefore, for methane alarm arrangement, it is suggested that the layout height on the side wall can be appropriately reduced with greater slope.

Key words: utility tunnel, leakage diffusion, gradient, alarm time, numerical simulatio