长大管棚预支护技术在北京地铁4号线西单站暗挖段的应用

在对国内外已有管棚施工技术的回顾与分析基础上，根据北京地铁4号线西单站暗挖段管棚设置的限制条件，充分考虑各种因素的影响，选择并成功实施了导向钻成孔、多次扩孔、前拉后夯的综合施工方法。介绍该工法施工关键技术，包括施工总体方案、主要施工工序、主要技术参数及工艺要求、施工精度及质量控制措施等。

The Application of Long and Large Pipe Roof Pre-Lining Techniques in Station Hidden Digging Section

Based on retrospection and analysis of the existing pipe roof techniques at home and abroad, according to the restrictive conditions of pile roofs in Xidan Station hidden digging section of Beijing Subway Line 4, a comprehensive construction method is chosen and successfully executed, including directional hole drilling, multiple back-reaming, combination of pull and punning. The key construction technologies summarized are construction general planning, main construction sequences, the principal technical parameters and process requirements, construction accuracy and quality control measures. The surface settlement or bulge induced by pipe roofs construction in Xidan Station is very small, with no effect on ground surface. During the excavation of the tunnel, the crown of arch soil is stable, and the crown settlement is very small. The accuracy of pipe roofs construction satisfied the end vertical limit of finite space between reinforced concrete top beams. As the pre-lining measures, the pipe roofs form the entire stable state with surrounding ground and preliminary lining, and the effect of pre-lining reinforcement is evident.