厚覆盖土层地区根式基础应用与试验研究

Applied and experimental study on the root foundation in the thick covering stratum region

针对厚覆盖土层地区地基承载力低的难题,提出了一种新型基础形式——根式基础。为了研究根键的加固效果及根式基础的适应性,以马鞍山长江大桥为背景,开展了根式基础的竖向承载力试验研究。试验采用自平衡测试法。研究内容包括普通沉井基础与根式基础的竖向承载能力与承载变形特性,两种基础形式在不同持力层条件下的承载特性及适应性等。试验结果表明:根键带动周围土体共同发挥作用能显著提高基础的竖向承载能力。根式基础在以砂土层和卵石层作为持力层时,竖向极限承载力分别提高了约100%和63%;根式基础在厚覆盖土层中具有很好的适应性,在加载初期便表现出提高基础竖向承载能力的效果,且随着加载值的增加其提高效果更加明显。在厚覆盖土层地区可以考虑用根式基础替代传统沉井基础或摩擦型桩基础,在大跨径桥梁建设中进行推广应用。

According to the situation of the shortage of the bearing capacity of the soft and thick covering stratum,the root- caisson foundation,a new type of caisson foundation with variable cross-section,was introduced. The self-balanced test method was utilized in the field tests to investigate the vertical bearing behavior of a root-caisson foundation and a traditional one. The mechanism of vertical bearing capacity root-caisson foundation was analyzed,and the improvements of bearing capacity due to the soil compaction and the bending resistance of roots were discussed. The results indicate that the rootstalks are capable of activating a large range of soil to bear the load,and with reasonable installation of rootstalks,the ultimate bearing capacity of a root foundation is greatly larger than that of a traditional caisson foundation.Compared with the traditional caissons,the vertical bearing capacity of root-caisson foundations could be increased roughly by 100% and 63% in different bearing layer. Root foundation owned the good adaptability in thick covering stratum region. At the early stage of loading,the root foundation then had showed that it owned the ability to enhance the vertical bearing capacity and the enhancement effect was more obvious with the loading increasing. Root foundation could be considered to replace the traditional open caisson foundation or friction pile foundation in the thick covering stratum region.