| The Huai-Shao-Heng railway is one of the country’s rapid passenger traffic passagewhich passed through the Xuefeng mountain mainly by the manner of the tunnel. The terrains of passing districts are changeful due to it belongs to low mountain area of tectonic erosion. According to the preliminary survey data and the combustion phenomena of partly work surface, it can be concluded that the gas comes from the shale. The existence of the shale gas not only affects the design standards of railway tunnel engineering, and it will produce great influence on the following project construction and operation safety.This paper takes the five tunnels of shale gas which passed through the Xuefeng mountain as the study objects, through the analysis of the regional stratigraphic features and structural characteristics, it is determined that the harmful gas in past projects mainly comes from shale(gas). Based on the field survey, monitoring data and previous research results, the shale gas in the drillings of the tunnel area of the Xuefeng mountain is tested and analysed using several methods mainly including field geological investigation, rock sample testing, well logging, mud logging, drilling and field desorption and so on. Combining the analysis of previous similar project cases, some reference opinions are proposed for the five tunnels design standards and the engineering prevention measures in the following constructions process at the he Huai-Shao-Heng railway of Xuefeng mountain area.The monitoring analysis results show that the cambrian neat’s foot pond group and the ordovician strata of the Xuefeng mountain area of the west Hunan province which the Huai-Shao-Heng railway tunnel passed exists the harmful gas, and the shale gas concentration, organic carbon content and maturity, the types of kerogen, permeability and other related indicators have achieved the conditions of shale gas generation, storage, release and migration. The contents of shale gas in the west route plans of Liangshan tunnel and the south Xuefeng mountain tunnel of the Huai-Shao-Heng railway in Xuefeng mountain area is less than other three tunnels, so those two tunnels construction and operation safety may not be affected, but it is needed to strengthen the advanced prediction, gas detection and construction ventilation in the process of tunnel constructions. The contents of shale gas in the eastern route projects of the Liangshan tunnel, Cangqianling tunnel and Lashujiao tunnel is more than other two tunnels. Therefore, it should be designed according to the low gas tunnel with reference to the current standard and in order to prevent the project risk effectively, the advance geological prediction and the gas detection must be strengthen in the process of tunnel construction. Meanwhile, for the purpose of dilute the gas concentration, reduce the gas accumulation, effectively eliminate its harm in engineering and prevent major disasters, guarantee the safety of tunnel construction and operation, it is also needed to strengthen the ventilation in the process of tunnel constructions. |
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