黄土地区长短组合桩的承载力及变形特性试验研究

黄土地区新型桩基问题研究匮乏,为了在黄土地区引入并推广长短组合桩基础,需深入研究该桩基的承载性状。研制了室内模型试验装置,在单桩、4根组合桩及8根组合桩工况下通过伺服加载系统对试验装置进行了加载,全面地分析了桩身承载力和变形特性。结果表明:桩身轴力和侧摩阻力的发挥具有异步性,长桩的破坏形式为刺入型破坏,但短桩不是很明显;在4根桩组合试验工况中,桩身承载力极限值与单桩略相等,桩侧摩阻力最大值出现的位置与单桩相比有所不同,长桩分担的荷载比例比短桩高;在8根桩组合试验工况中,在每级荷载作用下角桩的桩身荷载均比边桩、中心桩都大,与单桩承载力相比,其长桩(角桩、边桩)和短桩(中心桩)的桩身承载力及桩侧摩阻力均有显著的提高,角桩的桩顶荷载分担比略高于边桩。

Bearing capacity and displacement characteristics of long-short composite piles in loess areas

The researches on new pile foundation are insufficient in loess areas. In order to introduce and promote the composite pile foundation with long and short piles in the loess areas, the bearing characteristics of pile foundation need to be further studied. The laboratory model test apparatus is developed. The model test apparatus is loaded through servo loading system under the single-pile, four-pile and eight-pile working conditions, and the bearing capacity of pile and deformation characteristic are comprehensively analyzed and studied. The results show that the axial force of pile and the side friction play with asynchrony, and the failure mode of the long pile is the pricking destruction, but the short pile is not obvious. Under the composite test of four-pile working condition, the limit value of bearing capacity of the pile is equal to that of the single pile, and the occurrence of the position of the maximum of skin friction is different from that of the single pile. The load-sharing ratio of the long pile is more than that of the short pile. Under the composite test of eight-pile working condition, the load among the corner pile is more than that of the edge pile and center pile under each stage loading, and the bearing capacity and the skin friction of the long piles (corner pile, edge pile) and short piles (center pile) obviously decrease compared with those of the single pile. The load sharing ratio of the corner pile is a little more than that of the edge pile.