刚性桩复合地基承载及变形特性试验研究

Experimental Research of Load Bearing and Deformation Characteristics of Rigid Pile Composite Ground

通过现场试验 ,测出了刚性桩复合地基各土层的变形、桩体的上下刺入量、桩身轴力、侧摩阻力 ,并由此得到桩土荷载分担比、应力比 .试验表明 :垫层起到了使桩土共同参与工作的作用 ,使土能够较充分发挥其承载能力 ;单桩复合地基中加固层压缩是产生沉降的主要原因 ,下卧层的压缩量很小 ,垫层压缩量占沉降的比例随荷载而变化 ;单桩复合地基首先是桩周土承担较大荷载 ,使其从局部剪切破坏开始 ,逐步向整体剪切破坏发展 ,而后随着桩承担荷载的加大 ,桩承载力达到极限而破坏 。

A field test of rigid pile composite ground was conducted. The ground deformation, the axial force on piles and the upper and lower penetration into the cushion and the substratum were measured. Based on these measurements, the pile friction, the pile-soil stress ratio and the load-bearing proportion of piles and soil were investigated. The test results show that piles and soil bear a significant proportion of load due to the adjustment by the cushion, and usually the load-bearing capacity of soil can be fully utilized. The compression of the pile-reinforced layers accounts for a large proportion of the total settlement of the composite ground. The compression of the substratum is relatively small and the proportion of the cushion compression to the total settlement varies with loading levels. At the early stage of loading, soil bears a larger proportion of load, so a local shear failure occurs in soil and a general shear failure develops gradually. Then piles take much more load during the subsequent loading. When load on a pile reaches its load-bearing capacity, the failure of the composite ground happens.