深基坑内支撑支点水平刚度系数的解析解计算方法研究

排桩(墙)加内支撑结构是深基坑支护常采用的支护结构,内支撑支点水平刚度系数是支护结构设计计算的重要参数之一。基于受压杆件的应力应变线弹性理论和变形协调假定,对水平对撑(简称对撑)、水平对撑带八字撑(简称八字撑)、水平斜撑(简称斜撑)、水平角撑(简称角撑)、竖向斜撑、水平环形撑(简称环撑)、带放射撑的单环环形撑(简称单环撑)以及带放射撑的多环环形撑(简称多环撑)等8种基本内支撑结构的支点水平刚度系数进行了解析解的推导,提出了8种基本内支撑结构的支点水平刚度系数的计算公式,利用算例对其中常见的四类内支撑结构的支点水平刚度系数进行了演算,并采用有限单元法进行了复核,结果表明,解析解与有限元法计算的结果相符程度较好,解析解可作为支护结构单元计算的初始输入数据。补充完善了现行国家行业标准《建筑基坑支护技术规范》(JGJ120-2012)仅提供了水平对撑的支点水平刚度系数计算公式的不足,可供深基坑工程设计、施工人员参考。

Analytical methods for horizontal stiffness coefficient at pivots of inner support structures in deep foundation pits

The row piles with inner support structures are often used for retaining and protection of deep foundation pits, and the horizontal stiffness coefficient at the pivots of inner support structures is one of the most important design parameters of retaining and protection structures. In view of the stress-strain linear elasticity theory and deformation coordination hypothesis for compressed bars, the analytical solutions of horizontal stiffness coefficient at pivots of eight basic types of inner support structures face-to-face support, splayed support, inclined support, angle support, vertically inclined support, ideal-ring support, single-ring support and polycyclic-ring support are derived. The formulae for calculating the horizontal stiffness coefficient of the above eight structures are put forward. The horizontal stiffness coefficients of four commonly-used structures are calculated through examples, and the finite element method is used for checking. The results show that the analytical solutions are in good agreement with those calculated by the finite element method, and they can be used as the initial input data for calculation of support structures. This research improves the deficiency that the “Technical specification for retaining and protection of building foundation excavations JGJ120—2012” only affords the formula for calculating the horizontal stiffness coefficient at pivots of horizontal face-to-face support, and the research results can be used as a reference for the design and construction personnel in deep foundation pit engineering.