黏性土中倾斜荷载下抗拔桩的模型试验研究

为研究黏性土地基中抗拔桩在不同倾斜荷载情况下的承载机理,开展了抗拔桩室内模型承载试验.对比试验结果表明,抗拔桩承受倾斜荷载时,与竖向承载不同,呈现靠倾斜荷载一侧的桩周土体始终受压,而另一侧土体始终受拉的现象.达到极限时,仅靠荷载一侧桩周一定深度土体破坏,破坏区域在地表大致呈现扇形分布,其范围随荷载倾角增大而增大.此外,极限抗拔承载力随着倾角的增大而增大.在此基础上,依据破坏模式建立了倾斜荷载下抗拔桩的计算模型及桩周土体的破裂面方程,并基于单元体极限平衡分析得出了抗拔桩极限承载力计算公式.与试验结果对比表明,该方法计算值与实测值吻合较好.

Study of Model Experiments on Uplift Piles in Clay under Oblique Loads

Laboratory model tests on steel piles embedded in cohesive soil were carried out to study the transformation law in relation to ultimate uplift capacity and displacement patterns of uplift piles subjected to oblique loads. The test results show that the side of the pile near the oblique load is always under pressure, while the other side is in tension all the time, which differs from the uplift pile subjected to vertical loads. After reaching the ultimate capacity, soil in some depth is cracked only around the side close to oblique load. The failure surface occurs below the top of the pile. The failure area on the earth surface is distributed as a fan, whose range becomes larger with the increasing inclination of loads. Meanwhile, the ultimate capacity of piles increases with the increase of the inclination angle. On this basis, the calculation model of uplift piles subjected to oblique loads and the formula of failure surface around the pile were established based on the failure mode. Moreover, according to the analysis on the equilibrium conditions of the soil element, a formula for estimating the oblique capacity of uplift piles in clay soil subjected to oblique loads was also proposed. The predictions agree well with the test results so that the formula can be used in practical engineering.