锚索修复大变形抗滑桩预应力上、下限值计算方法

施加预应力锚索是修复大变形抗滑桩工程常用的技术之一，而锚索预应力的计算是修复工程设计的关键。基于弹性桩基本理论定义"大变形抗滑桩"概念，界定抗滑桩修复工程中锚索预应力上、下限值对应的桩顶位移状态；以修复上、下限状态的桩顶位移为设计目标，将抗滑桩自由段假定为悬臂梁，嵌固段假定为弹性地基梁，利用桩-索位移变形协调条件，分别推导锚索预应力上、下限值表达式，并将所提计算方法应用于预应力锚索修复大变形抗滑桩模型试验。结果表明：采用所提计算方法与模型试验获得的锚索预应力上、下限值误差仅6%，施加预应力锚索改善了大变形抗滑桩桩身受力性能，修复效果较好，验证了此方法的合理性。现场工程应用表明：某特大滑坡大变形抗滑桩桩顶位移得到有效遏制，抗滑桩工程处于稳定状态，进一步印证了所提方法的正确性。

Calculation of Upper and Lower Limits of Prestressed Anchor Cable to Repair Anti-slide Pile with Large Deformation

The use of prestressed anchor cables is one of the most common methods for repairing anti-slide piles with large deformation, and the calculation of prestress in anchor cables is the key to engineering design for such repair. Based on the basic theory of elastic pile, the concept of anti-slide pile with large deformation was defined, and the displacement of pile tip was proposed for upper and lower limits of prestressed anchor cable for the repair of anti-slide pile. The upper and lower repair displacement were considered the design objectives. The freedom and build-in sections of the anti-slide pile were supposed to act as cantilever and beam, respectively, on the elastic foundation. Next, expressions giving the upper and lower limits of the prestressed anchor cable were deduced using deformation coordination of pile cable displacement. The calculation method was used for the prestressed anchor cables to test a model for repairing large deformations. The results reveal that the error in the upper and lower limits of prestressed anchor cable obtained using this method is only 6%. This indicates that the prestressed anchor cable can improve the bearing performance of anti-slide piles with large deformation, and the repair is satisfactory. The rationality of the method is thus verified. Site engineering application reveals that the displacement at the tip of the anti-slide pile is contained effectively in cases of catastrophic landslides, thereby providing additional verification of its validity.