基于均匀设计的带桩帽钢管减沉桩承载性能试验研究

Study of bearing performance of steel pipe settlement reducing pile with pile cap based on uniform design

采用均匀设计法对桩长、桩距、垫层、桩帽对减沉桩承载性能的影响进行室内模型试验研究。通过6组3×4群桩试验,对不同沉管隧道荷载作用下的土压力、桩身轴力及沉管隧道沉降进行测定。由于采用均匀设计,运用数理统计理论工具对试验数据进行相关性分析和回归分析,从而区别于传统的单因素优选法,使得同时考察多因素、多水平作用下对沉管隧道沉降的综合影响成为可能。分析结果表明,桩长、桩距、桩帽对沉管隧道沉降的影响随着外荷载的增加而改变;垫层厚度和桩帽存在交互作用,两者共同对沉管沉降产生影响。最后,利用拟合结果进行反演分析,在总样本为432种减沉桩组合中找出符合沉降控制要求的最优化组合。反演结果在后续模型试验中得到较好的验证。

Based on the uniform design, the influence of pile cap, cushion, pile spacing and pile length on bearing capacity of settlement reducing pile foundation has been researched through six lab model tests with 3x4 pile group. Earth pressure, axial force of pile shaft, and tunnel settlement are measured under the different load of immersed tunnel. Owing to the application of the uniform design, the test data can be analyzed with the mathematical statistics methods such as correlation and regression analysis, and the significant degree and influence effect of the four influence factors on the settlement are estimated. Different from the traditional single factor optimization, this approach makes it possible to study the comprehensive influence of the pile foundation on the tunnel settlement under the multi-factor and multi-level conditions. The result shows that the influence of pile length, pile spacing and pile cap on tunnel settlement varies with the increase of the external load, and that the cushion and the pile cap interacts with each other, having a joint effect on the tunnel settlement. Finally, with the back analysis based on the fitting results, one optimum combination is obtained among 432 combination forms and verified in the successive test, which provides a new effective and practical way for theoptimum design.