Abstract: Two open tunnel boring machines bored the left and right line preparatory tunnels of a tunnel of the advanced bid doubletunnel and onebridge project. During the drillandblast construction, waterrich Grades Ⅳ, Ⅴ, and Ⅵ surrounding rocks with soft and hard soils were encountered. As a result, the principle technology varies with lithology, active treatment, and vibration reduction is adopted. Furthermore, techniques such as bench change and automatic blasting, threebench reserved core soil and annular pilot tunnel loose blasting, cutting before blasting and edge cutting by hydraulic top heading milling excavation and lower bench loose blasting, top heading hydraulic hammer excavation and edge cutting by scarifier, and arch foot weak blasting are employed, resulting in successful completion of preparatory tunnels.

Key words: plateau railway tunnel, preparatory tunnel, vibration reduction, smooth blasting, reserved core soil