荷载裂缝几何形态对管片外排钢筋锈层分布的影响

针对盾构隧道管片在服役期间出现外弧面开裂及外排钢筋锈蚀的问题，利用扩展有限元方法（XFEM）分析了不同荷载作用下拱腰处管片外弧面裂缝的几何形态，并结合达西定律建立了考虑管片裂缝几何特征的水分传输计算模型，在此基础上研究了荷载裂缝对管片外排钢筋锈层分布的影响。研究表明:在外部荷载作用下，拱腰处管片外弧面的裂缝形态近似为等腰三角形，且同等荷载作用下管片边部的裂缝最深；管片外排钢筋的纵向锈层形态类似“人”字形曲线，裂角越大，钢筋的纵向锈蚀范围越宽；管片钢筋在圆周方向的锈层形态类似椭圆形曲线，其不均匀锈蚀系数主要受裂缝深度的影响，裂缝深度每增加20 mm，不均匀锈蚀系数将增大3%~6%。

EFFECT OF GEOMETRY FORM OF LOAD CRACK ON RUST LAYER DISTRIBUTION OF OUTSIDE STEEL IN SEGMENT

Realizing the problems of outer arc surface crack and outside steel corrosion in existing shield tunnel segments,the paper analyzed the geometric form of crack on outer arc surface at arch waist of segment under different loads by extended finite element method(XFEM).According to the Darcy's law,the water transfer calculation model considering the geometric characteristics of segment crack was established.Based on that,the influence of load crack on the rust layer distribution of outside steel in segment was studied.The results show that:Under external load,the crack form on outer surface of shield segment at the arch waist is like a isosceles triangle,and the crack depth reaches maximum at the edge of segment under the same load;The form of rust layer of outside steel in longitudinal direction is like a“herringbone”curve,and the larger the crack angle,the wider the range of longitudinal corrosion;The form of steel rust layer in segment in circumferential direction is like an elliptical curve,and the non-uniform corrosion coefficient is affected by the crack depth;as the crack depth increases by 20 mm,the non-uniform corrosion coefficient increases by 3%~6%.