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当前煤与瓦斯突出物理模拟试验多采用二氧化碳代替甲烷,导致试验结果偏差较大。为了保证模拟试验相似性并规避甲烷气体带来的安全风险,提出了甲烷相似气体的概念。基于瓦斯在突出过程中的作用机制和相似准则,结合煤与瓦斯突出防治规定,建立了以瓦斯含量、瓦斯放散初速度、初始瓦斯膨胀能和含瓦斯煤力学性质为参数的相似指标。初步采用二氧化碳体积分数为20%、40%、60%、80%的二氧化碳和氮气二元混合气体作为甲烷相似气体的筛选气体。按照相关规范,分别测定了甲烷和筛选气体的相似指标参数值,确定了与瓦斯含量、瓦斯放散初速度、初始瓦斯膨胀能和含瓦斯煤力学性质接近的混合气体组分分别是二氧化碳体积分数为60%、35%、45%和54%。相关性分析结果表明,上述4种配比气体与甲烷性质相关性高,可以作为相似气体的待定气体。采用待定气体和甲烷进行了模拟试验,结果表明,二氧化碳体积分数为45%的混合气体的突出现象和突出临界值与甲烷接近,与甲烷相似性高。
Current physical simulation of coal and gas outburst more use of carbon dioxide instead of methane, resulting in large deviation test results. In order to ensure the similarity of simulation tests and avoid the safety risks caused by methane gas, the concept of methane-like gas is proposed. Based on the mechanism and similarity criterion of gas in salient process and combining with the prevention and control regulations of coal and gas outburst, the similar indexes of gas content, initial gas dissipation rate, initial gas expansion energy and mechanical properties of coal gas are established. A binary mixture of carbon dioxide and nitrogen with 20%, 40%, 60%, and 80% carbon dioxide gas volume fraction was used as the screening gas for methane-like gas. In accordance with the relevant norms, the parameters of similar indexes of methane and screening gas were respectively determined, and the components of gas mixture close to the gas content, initial velocity of gas emission, initial gas expansion energy and the mechanical properties of coal gas were determined as follows: the volume fraction of carbon dioxide 60%, 35%, 45% and 54%. Correlation analysis results show that these four kinds of matching gas have high correlation with methane properties and can be used as gas to be determined. A simulation experiment was carried out on the gas to be determined and the methane. The results show that the prominence and the prominent critical value of the mixed gas with the carbon dioxide content of 45% are close to those of methane with high similarity with methane.