根式基础竖向承载力模型试验研究

Model test study on vertical bearing capacity of root foundation

在桥梁设计和施工中大跨度跨河桥梁基础一直是设计施工的难题,因此针对厚覆盖层地质条件提出了新型变截面基础形式——根式基础的概念。文章进行了根式基础的模型试验,即无根键、布置1层根键和均布5层根键的模型试验。竖向承载力试验采用杠杆方式加载。试验结果表明:布置1层根键时极限承载力比无根键提高13.54%,布置5层根键时提高73.14%;有根键时桩身轴力曲线与桩侧摩阻力曲线趋势与无根键基本一致,但有根键时桩侧摩阻力发挥更加充分,跨越根键处轴力下降较快;布置根键在减少工程量、降低造价的同时大大提高了基础承载力。

The long span river-crossing bridge foundation has always been a problem for bridge design and construction.In this paper,a new type of basic foundation of variable cross section is proposed based on the geological conditions of thick overburden,namely root foundation.The model test of root foundation is made,the test involved only a foundation without root,a foundation of one-layer root and a foundation of uniform five-layer root.The vertical bearing capacity test is carried out in a leveraged manner.Test results show that the vertical bearing capacity of the one-layer root foundation and the five-layer root foundation is 13.54%and 73.14%higher than that of the rootless foundation,respectively.When the foundation has root,the axial force curve and the lateral friction curve are basically the same as those of the rootless foundation,but the lateral friction plays a better role in bearing the load,the axial force drops rapidly when crossing the root.Arranging roots can reduce the amount of work and cost,while greatly improving the basic carrying capacity.