水平循环荷载下砂土中沉井加桩基础累积变形特性

Cumulative deformation of a caisson-piles composite foundation in sand subjected to cyclic lateral loading

采用自主设计的水平循环加载装置进行模型试验,探讨单向、不完全对称及双向对称循环加载路径下沉井加桩复合基础及沉井基础的变形特征与位移预测模型。模型试验表明:在近一万次循环荷载作用下,基础的水平循环累积位移随循环次数的增大先增大后逐渐趋于稳定,呈两阶段变化特征,并且其大小受循环加载路径的影响较大,同时,与沉井基础相比,沉井加桩复合基础显著提高了基础抵抗水平循环变形的能力。最后,在对模型试验结果回归分析的基础上建立水平循环累积位移预测模型,并且其能较好地对不同循环加载路径下的基础变形进行预测。

Model tests were carried out using a lateral cyclic loading device developed in-house. The lateral cyclic deformation and the displacement prediction model of a caisson-piles composite foundation and a caisson foundation were investigated under one-way and two-way cycling loading in symmetric and asymmetric forms. The model tests with approximately 10 000 cycles revealed that the cyclic cumulative displacement of the foundation behaved with two characteristic phases, firstly increasing rapidly with the increase of cycles and then gradually being stable. The magnitude of cyclic cumulative displacement was significantly affected by the cyclic loading path. Compared with the caisson foundation, the caisson-piles composite foundation improved significantly the ability of the foundation in resisting the lateral cyclic deformations. Finally, the prediction model of cyclic cumulative displacement was established on the basis of regression analysis of the model tests results. It was shown that the prediction model predict effectively the cyclic cumulative displacement under different cyclic loading paths.