Abstract: Superficial natural gas contained in strata would bring safety risks to tunneling. The position of the regional structures, the lithology, the relationship between the superficial gas formation and the gas storing layers, the influence of the types and development features of the natural gas storing layers on tunneling are studied in detail, with Meilingguan tunnel on LanzhouChongqing railway as an example. Gas prevention and control measures are proposed on basis of the actual situation of the gas emission after excavation and analysis on the gas emission rules. The degree of the influence of the superficial gas on the construction of Meilingguan tunnel is provided.

Key words: LanzhouChongqing railway, Meilingguan tunnel, superficial natural gas, stratum lithology, gas formation and gas storing layer, gas emission 