隧道内埋地燃气管道泄漏扩散规律研究

目的隧道内埋地燃气管道发生泄漏后燃气易积聚达到最低爆炸极限浓度,产生爆炸危险,需要对管道泄漏后在土壤和空气环境中连续扩散的问题进行研究。方法采用理论分析和数值模拟的方法,对土壤和空气区域中的燃气浓度进行同时连续的监测。结果①小孔泄漏发生后10 min、20 min、30 min、40 min时刻甲烷体积分数值为0.05的等值线在土壤内的最大扩散半径分别为0.90 m、1.15 m、1.25 m和1.30 m,甲烷在土壤内的最大扩散半径在10~15 m之间；②泄漏发生约5 min后土壤内各点处甲烷浓度趋于稳定；③空气区域中甲烷体积分数随时间的变化分为快速增长、缓慢增长和稳定3个阶段,泄漏发生60 min后隧道顶部6 m长的区域处于爆炸极限浓度范围内。结论隧道内埋地燃气管道发生泄漏后,燃气在土壤内扩散半径不超过15 m,相对封闭的隧道环境使得隧道顶部6 m区域处于爆炸极限浓度范围内,需加以防控。 

Study on leakage and diffusion law of buried gas pipeline in tunnel

ObjectiveAfter the leakage of the buried gas pipeline in the tunnel, it is easy for the gas to accumulate and reach the minimum explosion limit concentration, resulting in explosion danger. Thus, it is necessary to study the continuous diffusion of gas in soil and air environment after pipeline leakage. MethodsThe gas concentration is monitored continuously by theoretical analysis and numerical simulation. Results(1) At 10 min, 20 min, 30 min and 40 min after the occurrence of small hole leakage, the maximum diffusion radius of the isoline with the volume fraction of CH₄ of 0.05 in the soil was 0.9 m, 1.15 m, 1.25 m and 1.30 m, respectively while the maximum diffusion radius of CH₄ was between 10 m and 15 m; (2) CH₄ concentration in the soil tends to be stable after the leakage for about 5 min; (3) The variation of CH₄ volume fraction in the air area with time can be divided into three stages:rapid growth, slow growth and steady state. When the leakage lasted for 60 min, the 6 m-long area at the top of the tunnel was in the range of explosion concentration limit. ConclusionsAfter the leakage of buried gas pipeline in the tunnel, the diffusion radius of gas in the soil should not exceed 15 m. The relatively closed environment in tunnel makes the 6 m-long area at the top of the tunnel within the limit concentration of explosion, which needs to be controlled.