基于FLAC软件的气压沉井刃脚反力计算

Resistance of Pneumatic Caisson Cutting Edge Computed by FLAC

采用显式有限差分程序FLAC,模拟计算环形沉井基础切口处的刃脚反力。计算时,假定土体服从Mohr-Coulomb强度准则和关联流动法则。该方法的优点是可以避免对滑移面的任意性进行假设,方便利用不规则形状单元适应模拟各类复杂边界,并可把多种影响土体最终极限承载力的因素(如内聚力c、内摩擦角φ、重度r以及表面超载q等)综合考虑到一起,从而较为精确地计算沉井基础的刃脚反力。最后,把计算结果与已有结果及现场测试结果进行了比较。结果表明,用FLAC计算其结果比用Bolton&Lau、Kumar计算和用Vesic公式计算的结果都小,与Terzaghi公式计算的结果较为吻合,和现场实测结果最为接近。

The explicit finite difference method was used to compute the caisson cutting edge resistance in this paper. A Mohr- Coulomb yield criterion and the associated flow rule were assumed for the soil mass behavior in the computation. This method has the advantages in that the assumption for arbitrary slip line surface can be avoided. In this method it is convenient to use irregular elements to simulate all sorts of complicated boundary conditions, and many soil physical parameters such as cohesion, internal friction angle, gravity, surcharge, etc. are synthetically considered into a single integrated problem in the computation. Compared with the results derived from theTerzaghi＇ s formula, Vesic＇ s revised formula and Kumar and Bolton ＆ Lau＇ s slip line method, the computed result by this method agreed well with that from the Terzaghi＇ s formula and was very close to the in-situ measurement value.