大跨度公路隧道交叉分岔段施工方案研究

Study on Construction Method for Intersectional Turnout of Large Span Highway Tunnel

由于支隧道的存在,交叉段结构受力复杂,围岩应力高度集中,给施工带来很大困难。为获得交叉段合理施工方案,以四川雅砻江官地水电站内交通工程——隧道交叉段实态建模,进行5种可能方案的三维施工数值研究。结果表明,每种方案中交叉段围岩的竖向位移和应力集中程度均较其他部位高20%以上;开挖后立即支护或分部开挖,可明显降低交叉部围岩的应力集中程度;对交叉部控制截面进行线型优化,可改善裸洞受力情况。研究结论对设计、施工交叉隧道有一定指导意义。

The complex bearing conditions of intersection and high concentration of surrounding rocks due to branch tunnel cause a significant dificulty in construction. In order to obtain reasonable construction method, five options of tridimensional construction numerical study are carried out based on practical modeling of tunnel intersection for traffic engineering in the Yalong River Guandi Hydropower Station in Sichuan Province. The results indicate that the vertical displacement and concentration degree of stress of surrounding rocks at intersection for each option are over 20% higher than other locations; supporting timely after excavation or partial excavation can significanOy reduce the concentration degree of stress of surrounding rocks at intersection; optimizing the alignment of the intersection can obviously improve the stress of naked hole. The research conclusions may be useful for guiding further research of design and construction of intersection tunnel.