Abstract: The distribution, vertical and horizontal limits, pressure as well as flow rate of the shallow buried toxic gas along the alignment of a regional railway was quantified in the preliminary subsurface investigations. A trial toxic gas release test section was set up between tunnel station DK51+661 and DK51+709 to verify the design parameters, such as safe distance for the gas release boreholes, safe pressure limits, gas flow rate and ground subsidence information. The results of the trial test section would provide valuable information for the tunnel design and construction.

Key words: Toxic Gas, Safe Distances, Safe Pressures, Effective Stress, Ground Subsidence