考虑附加应力作用的桩锚支护结构稳定性与位移关系研究

Relationship between the displacement and stability of pile anchor retaining structure considering additional stress

桩锚支护结构应用日益广泛,然而在基坑开挖过程中,基于锚杆预应力的基坑稳定性与位移的量化关系尚未解决。同时考虑锚杆预应力引起的附加应力对基坑稳定性和位移的影响,分别得到预应力与桩锚支护结构基坑整体稳定性安全系数、水平位移的计算公式,以及基坑整体稳定性安全系数与水平位移二者之间的关系表达式;通过典型基坑工程实例与现行通用基坑设计软件计算结果进行对比。结果表明:(1)将预应力以附加应力形式来计算基坑整体稳定性安全系数,安全系数随着预应力增加而增加,二者呈非线性关系;(2)以预应力在土体中产生的附加应力形式来计算桩锚支护结构水平位移,支护结构水平位移随着预应力增加而减小,二者呈非线性关系;(3)给出的支护结构稳定性安全系数和支护结构水平位移之间的关系表达式,更加符合理论与工程实际;(4)现行桩锚支护结构设计偏于保守,考虑预应力的基坑稳定性和位移计算方法,仍需根据大量工程实践进行验证与修正。(5)首次考虑附加应力作用的桩锚支护结构稳定性计算与水平位移关系研究,可为基坑开挖过程中的动态稳定性评价提供理论依据。

The pile anchors are used widely as supporting structure. But in excavation, the stability of foundation with the prestressed anchors and displacement hasn＇t been solved yet. Additional stress caused by prestressed anchors influences on the stability and displacement of foundation, the expression between prestress and the stability of the pile anchor supporting structure, and the equation of horizontal displacement and structure stability are formulated. In a typical foundation pit, comparisons of the calculation results by general design software show that： 1） The prestress is considered as additional stress to calculate the overall stability safety factor of foundation pit, and the safety factor increases with increasing prestess; there exists a non-linear relationship between the safety factor and prestess; 2） Similarly, the displacement of the pile anchor supporting structure can be calculated by the forementioned way; and horizontal displacement of retaining structure decreases as prestress increases, which presents a non-linear relationship; 3） The expression of relationship between the stability safety coefficient of supporting structure and the horizontal displacement of retaining structure is given, which is more suitable for theory and engineering practice; 4） Compared with the calculation method for stability and displacement of the foundation pit considering prestress, the existing design of the pile anchor supporting structure is conservative and still needs to be validated and corrected according to a large number of engineering practices. 5） We first study the relationship of stability of pile anchor supporting structure and horizontal displacement considering additional stress, which can provide theoretical foundation for dynamic stability evaluation of foundation pit in the process of excavation.