圆形钢筋混凝土桩局部破除后抗弯能力计算及应用

深基坑工程中常常出现围护桩成桩垂直度偏差以致侵入主体结构限界的现象，为保证后续主体结构尺寸符合要求，需要对侵限部位进行凿除，进而导致其抗弯承载能力下降。针对圆截面桩体局部凿除后的抗弯承载能力计算问题，基于二次逼近法，建立圆形钢筋混凝土桩局部破除后正截面抗弯承载能力计算方法，结合实际工程分析围护桩局部破除后对基坑围护结构体系的安全性影响。结果表明： 桩身局部破除后，纵向受力钢筋切断和桩身截面面积的减小将导致桩身正截面抗弯能力快速下降；依托工程中800 mm 的围护桩，凿除18 cm 厚度（含切断6根主筋）后，其正截面抗弯能力下降至原设计值的55%，剩余承载力已不能满足安全支护的要求，需进行加固处理。

Calculation of Bending Moment Bearing Capacity of Circular Reinforced Concrete Pile after Partial Excision and Its Application

The vertical deviation of retaining piles often occurs in deep foundation pit engineering, which would lead to the invasion of the main structure boundaries. In order to ensure the size requirements of the main structure, it is necessary to cut the invaded parts. After the pile is cut, its bending moment bearing capacity will inevitably decrease. For the calculation method of bending moment bearing capacity of circular reinforced concrete piles after partial excavation, the calculation method of bending bearing capacity of normal cross section of circular reinforced concrete piles after partial excavation is established based on the second approximation method. The influence of partial excavation of retaining piles on the safety of retaining structure system of foundation pit is analyzed based on practical engineering. The results show that: (1) The cutting of longitudinal bars and the reduction of the cross sectional area of the pile, due to partial removal of pile, are the main reasons for a rapid decline in the flexural strengthening of the pile. (2) In a practical engineering, the diameter of retaining pile is 800 mm, and after cutting 18 cm thickness of those parts beyond the boundary (6 main ribs being cut), its flexural capacity of normal cross section is decreased to 55%, which could not meet the requirements of safety support, hence reinforcement should be performed.