锚索间距对环锚预应力衬砌结构强度的影响与选择

以南水北调中线穿黄隧洞环锚预应力混凝土衬砌结构为例,利用有限元软件ANSYS建立计算模型,通过三维有限元计算并分析了环锚预应力结构中锚索间距对衬砌结构强度和稳定性的影响及其相关规律。结果表明,当锚索间距过大时,不能满足衬砌结构的承载能力及环向应力沿轴向的均匀性要求,局部区域因环向拉应力超过混凝土抗拉强度设计值时将出现裂纹;当锚索间距过小时,衬砌结构偏于安全,但影响工程施工的便利性并提高工程造价。对于穿黄隧洞工程,锚索间距为0.4~0.6m时可满足其安全运行要求,为尽可能降低锚索的工程造价,兼顾锚索的锚固作用及工程的经济效益,建议在满足工程结构受力的要求下优先选取较大的锚索间距。

Impact and Selection of Anchor Interval on Strength of Prestressed Lining Structure

Based on a case of prestressed concrete lining structure in Yellow River crossing tunnel project, which is the middle route project of South to North Water Transfer Project, analytical structural models were developed by using finite element software ANSYS. According to the numerical simulation results, the impact of prestressed structure anchor interval on strength and stability of lining structure were discussed and some rules were summed up. The results show that for prestressed concrete lining structures, the interval of anchor should not be too large for the carrying capacity requirements and uniformity requirements of hoop stress in the axial direction in lining structures, or there would be cracks in localized areas of lining as that the hoop tensile stress exceeds design value of concrete tensile strength; the anchoring effect of structure is on the safe side when the anchor interval is on the small side; however, the anchor interval should not be too small to avoid impacting construction convenience and causing high cost; the safe operation requirements of the Yellow River crossing tunnel project were met when anchor interval is between 0.4 m and 0.6 m; to take consideration of both anchoring effect and economic effect, the larger anchor interval is preferentially selected.