| For the case study of the Chengdu-Chongqing passenger railway, the geotectonic and oil-gas reserve background along the line are briefly introduced, and detailed investigation has been carried out on the main oil-gas fields and oil-gas bearing construction.The composition and space-time concentration characteristics of the shallow gas about the total10tunnels are acquired base on the data acquired from field tests and indoor experiments. And the tunnel gas hazards level is classified preliminarily.Then on this basis, combined with the geotectonic background and test results of the rock sample, the geological characteristics of the oil-gas storage are discussed mainly on: the relationship between the tunnel and the oil-gas construction; oil-gas bearing characteristic; oil-gas migration law; the correspondence between lithology and gas appearance.Finally, according to the reserve formula used by oil-gas industry, the shallow gas spillage and the maximum flow rate are discussed and the estimated values for them are calculated and the comprehensive tunnel shallow gas hazards level is classified respectively.The conclusions are as follows:(1) anticline is the favorable oil-gas construction, so the gas concentration is generally higher when tunnel crossing the anticline structure;(2) gas and lithology has good correlation. Sandstone, especially in the fracture rock section, makes himself a good bearing for shallow gas with a high gas concentration while mudstone makes the cap rock and the gas concentration is low;(3) the gas concentration has a good positive correlation to the drill depth, which means the concentration increases with the increase of the drill depth;(4) Longquanshan tunnel is classified as gas tunnel with a gas section ZK23+210-ZK25+900which should be designed and constructed under the regulation of gas tunnel. The other tunnels are low gas tunnels. |
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