Abstract: In this paper, some issues existing in current prevention and treatment design of tunnel crossing debris flow gullies are studied. Firstly, forms of tunnel crossing debris flow gully are summarized, and corresponding design key points and prevention measures for different crossing forms are put forward based on theoretical analysis and engineering analogy. Secondly, the optimal hydraulic section of drainage channel is further studied; the study results show that the smaller the section factor coefficient M of drainage channel, the better the hydraulic conditions; and the section factor coefficients of channels with different shapes are derived by taking straight wall accurate drainage channel as an example. Thirdly, the main causes for sludge accumulation in the drainage channel are analyzed; some current checking formulas for siltation in drainage channels are analyzed and sorted out; and a design checking method and flowchart of sludge accumulation prevention in the drainage channel is put forward based on formulas of channel width checking, mud depth in the channel and flow rate checking, etc. Finally, based on typical engineering examples, a reasonable tunnel construction scheme and shape and size parameters of drainage channel are designed.

Key words: tunnel engineering, tunnel crossing form, debris flow drainage channel, optimal hydraulic section, checking computation of silt prevention