自平衡试验与传统试验的比对研究

Comparison study on self-balanced tests and the traditional tests

本文介绍了原位试验过程,对一根原型桩分别进行了自平衡试验、抗压试验和抗拔试验,抗压试验过程中测量了荷载箱在分级荷载下的荷载,同时用钢筋计测量了桩身应力,分析了自平衡试验与传统静载荷试验中极限承载力的差异,得到了自平衡承载力转换为抗压、抗拔承载力的转换系数。试验结果表明,上桩的抗压承载力最大,自平衡承载力次之,抗拔承载力最小;有桩端支撑时,桩侧承担的荷载增加了29.04%,说明增加桩端阻力可以增加桩侧摩阻力;在自平衡载荷试验和抗压试验均达到极限状态时,自平衡试验的荷载箱受力荷载大于抗压试验时的荷载,说明自平衡试验对应的极限端阻力大于抗压状态下的极限端阻力;上桩在没有端承条件下的抗压承载力与自平衡承载力相等,说明在相同端承条件下,上桩的自平衡摩阻力与抗压摩阻力不存在明显差异。

The in-situ testing processes of the prototype piles are introduced. The in-situ tests including the self-balanced test, the compression test and the uplift test for the same pile are carried out. In the process of the compression test, the compressive load of the load cell in the grading load is measured, and the stress of the pile body is measured with a steel bar meter at the same time. The differences of the limit bearing capacity between the self-balanced load test and the traditional static load test are analyzed, and the conversion coefficients for the self-balanced bearing capacity converting to the compressive bearing capacity and uplift bearing capacity are obtained. The results show that the compressive bearing capacity of piles is the maximum value, the self-balanced bearing capacity is the middle and the uplift bearing capacity is the minimum. Under the effect of the pile end support, the load borne by the pile side increases by 29.04% , which indicates that the increase of the pile end resistance can increase the pile friction resistance. When the self-balanced loading test and the compression test are in the limit state, the bearing load of the load cell under the balanced test is bigger than that under the compression test, which shows that the ultimate end resistance from the balanced test is bigger than that from the compressive resistance. When without the effect of the pile end support, the bearing capacity of the compressive piles and the bearing capacity of the self-balance piles are equal, which shows that in the same end bearing condition, there are not the significant differences for the self-balancing friction and the compression friction.