广州地铁岩溶区盾构施工地层变形特性研究

以在建广州地铁盾构穿越岩溶填充区为依托,采用FLAC3D三维数值模拟程序,研究盾构施工力学行为,总结穿越岩溶填充区过程中围岩和管片变形特性。结果表明:围岩变形主要集中在岩溶填充区范围内,其位移明显要大于周围岩土体,特别是地质界面处前后2 m范围内,容易导致管片错位破坏,因此要加强设计参数;掌子面挤出变形基本上下对称分布,主要影响范围是掌子面前方6 m,其地层加固有效距离为6 m;盾构穿越地层发生变化时,管片纵向不均匀变形相当明显,主要表现为竖向位移,管片主要承受竖向力的作用,其力学行为表现为仰拱和拱顶向内弯折,而两侧变形向外弯折,应进行不对称配筋设计,以利于结构的安全性和经济性。

Study on deformation features of stratum during shield-driving tunnel of Guangzhou metro in karst area

Based on shield construction of Guangzhou subway tunnel across karst area,this paper adopted three-dimensional numerical simulation program FLAC3D to investigate construction mechanics behavior of shield and presented the deformation property of surrounding rock and shield segment.The research results show that deformation of surrounding rock are mainly concentrated in the karst filling area,displacement of which is significantly more than other area especially 2 m range around geological interface,and dislocation damage of shield segment is prone to take place.Consequently,this paper concluded that design parameters should be improved at geological interface,extrusion deformation of working face is in symmetrical distribution and its main effective range is 6 m ahead of working face,reinforced strata effective distance of which is 6 m,vertical asymmetry deformation of shield segment obviously appears when shield passes through changing stratum zone and displacement is mainly vertical,and invert arch and vault is inward bending due to shield segment being subjected to vertical pressure yet wall is outward bending,which means asymmetric reinforcement design should be carried out to improve safety and economy of segment.