桩撑式支护基坑通用弹性地基梁分析法

A General Analysis Method of Beam on Elastic Foundation for Pilebraced Deep Foundation Pit

弹性地基梁法常用于模拟分析桩撑(锚)式支护基坑在开挖、设撑等施工工况中变形和受力的变化。目前利用该方法对某工况基坑分析时,首先要将整个支护桩在支撑处划分为若干个桩段,然后利用相邻桩段交界处的位移连续条件和受力平衡条件,推导出相应的待定参数方程,之后再利用求出的待定参数分析支护体系(基坑)的变形和受力。由于不同施工工况对应的支撑数和桩段数不同,因此该方法必须根据不同工况重新推导各自的参数方程,从而导致计算过程繁杂,难以形成通用计算公式和方法,也不易编程等问题。通过将支撑与桩段归纳为3种基本连接形式(即支撑分别相连于桩顶、相邻两桩段之间和坑底),本文建立了相邻两个桩段间待定参数的递推公式,进而推导出了适用于内支撑和锚索支撑形式、任意支撑道数、开挖或设撑工况的通用待定参数方程。该方程仅含4个参数,远少于现有方法且易于求解。文中算例结果验证了本文方法的合理性和可行性。

The deformation and force of pile-braced(-anchored)deep foundation pit is commonly determined by method of beam on elastic foundation(MBEF)during its construction process of excavation and support setting case.The existing MBEF uses the following steps for analysis:Firstly,the entire pile is divided into several segments at the braces,and then the continuous conditions of displacement and force balance conditions at the junction of the segments are used to derive the corresponding equations of the undetermined parameters,and then the deformation and force of the supporting system(foundation pit)are analyzed by using the determined parameters.Due to the different number of supports and segments corresponding to different cases,the method must rederive their respective parameter equations according to different cases,which result in complicated calculation process,difficult to form general calculation method and program.In view of the above problems,a recursive formula is established for the undetermined parameters between two adjacent segments by summarizing the support and pile segment into three basic connection forms(namely,the support is connected to the top of the pile,between the two adjacent pile segments and the bottom of the pit),then deriving the general parametric equations applicable to strutted or anchored retaining structures,arbitrary number of supports and excavation or support setting case.The study results in this research verify the rationality and feasibility of the proposed method.