中文摘要：

针对基坑工程中锚索预应力损失的特殊性,采用现场试验的方法,对分级张拉直至破坏过程中锚索锚固体上剪应力的分布特征以及不同张拉荷载、循环加卸载下锚索预应力的损失规律进行了分析;结合工程实例建立数值模型,分析了锚索预应力在基坑分步开挖过程中的变化规律,并对一次张拉和分步张拉两种方案下支护桩的位移和弯矩变化进行了对比分析。结果表明：锚索锚固体前端的脱黏滑移是锚索初期张拉锁定损失的重要原因,张拉荷载越小、循环张拉次数越多,锚索的初期损失率越低;对于多排锚索支护桩,上排锚索预应力会因下排锚索施加而减小,而在整个开挖过程中,锚索预应力呈现波动增大的趋势;通过采取分步张拉控制措施,锚索预应力的张拉锁定及开挖损失均得以明显改善,支护桩在开挖过程中的受力和变形更趋合理,该控制措施可为类似基坑工程的施工提供借鉴。

英文摘要：

Owing to the prestress loss particularity of the anchor cables in foundation pits, field tests are conducted. The distribution of shear stress on anchorage body is tested in the load tensioned process, and the prestress loss laws under different tensile loads and cyclic loads are analyzed. Through the numerical model of a project example, the prestress change laws of anchor cables in pit excavation process are considered, and the displacement and bending moment of supporting piles are compared between measures of a single tension and tension by steps. The results indicate that the debond slip in the front section of anchorage body is an important factor in prestress loss in tensioned locking process, and that the loss rate of prestress will be reduced under more cyclic tensile times and lower tensile force. For the supporting piles with multi-row anchor cables, the prestress of anchor cables in the upper row will be reduced by the tension of anchor cable in the lower row, and the anchor cable prestress shows a tendency of fluctuating increase throughout the excavation process. Through the control measures of tension by steps, the prestress loss of anchor cables is significantly reduced in the tensioned locking and excavation process, meanwhile, the force and deformation of supporting piles are more reasonable in excavation process. Such control measures can provide a reference for the construction of similar projects.