超大断面小净距隧道方案优化研究

针对超大断面小净距隧道在施工效率和稳定性方面的矛盾,为了实现此类隧道的安全、快速修建,依托济南二环南路东延线浆水泉隧道工程,采用数值分析、现场实测与验证等方法,以特征点沉降、夹岩应力、初支安全度和屈服接近度四个物理量为评判指标,对不同方案的超大断面小净距隧道的施工力学行为进行研究,完成了浆水泉隧道进口段的方案优化工作。分析结果表明:不同方案的浆水泉隧道后行洞开挖均会对先行洞产生影响,按影响程度由大到小排序为两台阶法三台阶法CD法CRD法双侧壁导坑法,但多指标的影响度显示双侧壁导坑法未显著优于CD法和CRD法;从施工效率方面综合考虑,建议选用CD法进行施工。现场实践表明:CD法施工方案可以满足该段的围岩稳定性要求,从而有效缩短工期、降低成本,产生较好的经济效益和社会效益。基于多指标分析所形成的优化方法和实践经验可为类似地质条件下的超大断面小净距隧道的设计和施工提供技术和理论指导。

Study on scheme optimization of neighborhood tunnel with super large section

Neighborhood tunnel with super-large cross-section is widely used in highway tunnels in China. However，there are contradictions between surrounding rock stability and construction efficiency in such tunnels. In order to build them safely and quickly，the Jiangshuiquan tunnel engineering projecton the East extension of Jinan Second Ring South Road has been studied. The methods of numerical analysis，field monitoring and verification have been used to study the mechanical behaviors of tunnel under different construction schemes. During the study，several indexes have been adopted，such as characteristic point settlement，rock stress，safety degree of initial support and yielding approach index. The construction scheme optimization of tunnel entrance section has been completed. The results show that the construction of the back-hole of tunnel will have effects on the first-hole in all schemes. The effect degree is sorted from big to small: two-steps method ＞ three-steps method ＞ CD method ＞ CRD method ＞ both side heading method. However，the influence degree of multi-index shows that both side heading method was not significantly better than CD method and CRD method. In view of construction efficiency，CD method is suggested. Field practice shows that CD method can meet the stability requirements of surrounding rock. It shortens the duration and reduces costs，resulting in good economic and social benefits. The optimization method and practical experience based on multi-index analysis can provide technical and theoretical guidance for the design and construction of neighborhood tunnel with super large section under similar geological conditions.