关键词: 高原铁路, 浅埋偏压, 预加固, 悬臂掘进机, 安全进洞

Abstract: The grade Ⅵ surrounding rock at mix zone of slope wash soil and mudslide accumulation with shallow overburden and asymmetrical pressure at tunnel entrance is prone to collapse and landslide, resulting in difficult tunnel entering. As a result, the construction difficulties and rapid tunnel essential entering technologies of a plateau railway are studied. Main studies and conclusions are as follows: (1) The advance large pipe roof is employed to improve the surrounding rock strength at 30 m section of tunnel entrance. (2) 11 end piles and 34 t friction piles are arranged at tunnel entrance and sideslope respectively to solve asymmetrical pressure problem. (3) 1 054 jet grouting piles are arranged within 90 m zone on tunnel top to improve the stability of slope wash soil; a 198 mlong aqueduct is adopted to drain the water on tunnel top right, and the aqueduct is arranged at top of retaining wall innovatively to reduce the mudslide risk in rainy season. (4) The advance smallduct reinforcement and cantilever boring machine are adopted at grade Ⅵ surrounding rock at 30 m mix zone of tunnel entrance to minimize disturbance to surrounding rock; the construction sequence is improve from opencut first and then mining to mining first and then opencut according to construction requirements in winters. The application results show that the methods recommended can minimize the influence of tunnel entering construction on surrounding environment, shorten the construction period, and guarantee the construction safety.

Key words: plateau railway, shallow overburden and asymmetrical pressure, preconsolidation, cantilever boring machine, safe tunnel entering