千斤顶偏心荷载作用下盾构隧道管片裂纹扩展规律

Crack Propagation Law of Shield Tunnel Segment Under the Eccentric Load of Jack

盾构在穿越上软下硬复合地层时掘进姿态控制不佳,易出现千斤顶偏心,导致管片局部出现裂纹。基于扩展有限元理论,运用ABAQUS软件建立管片精细化三维模型,分析千斤顶向内、向外偏心时管片的裂纹形态、扩展规律和扩展路径。分析结果表明:初始裂纹出现在千斤顶偏心一侧的凸榫边缘,内弧面、外弧面、顶面与侧面均出现大范围网状裂纹;千斤顶向内弧面偏心时管片裂纹范围更广,数量更多,危害更严重;裂纹长度呈台阶递增,裂纹扩展可分为裂纹初始发展、裂纹协调发展、裂纹迅速发展3个阶段,在第3个阶段裂纹扩展最迅速,管片结构出现区域性破坏。

The shield machine has a poor driving attitude control and is easy to cause the eccentricity of jack when crossing through the upper-soft and lower-hard composite stratum,which will lead to a partial cracks in the segment.Based on the extended finite element theory, the fine three-dimensional model of segment was established by using ABAQUS finite element software, the crack shape,propagation law and propagation path of segment were analyzed when the jack is inward and outward eccentric. The results show that the initial crack appears in the edge of tenon on the eccentric side of the jack,a large scale of reticulate cracks appear on the inner,outer, top and side surface. Segment cracks are wider and have more quantity and more serious damage under the action of inward eccentric jack.Crack length increases step by step,crack propagation can be divided into such 3 stages as initial development of cracks,coordinated development of cracks and rapid development of cracks,crack growth is the fastest in the third stage and there would be regional destruction of the segment structure.