嵌岩工字钢桩承载力特性研究

BEHAVIORS OF SOCKETED H-SHAPED STEEL PILES

嵌岩工字钢桩广泛应用于香港地区,通过现场载荷试验及室内摩阻力试验对这种桩型的承载力特性进行研究。试验结果表明,在垂直载荷作用下嵌岩工字钢桩中的工字钢与周围混凝土界面上会有摩阻力产生,但两者又不能看作是一个复合整体。当荷载增加到一定程度时,钢/混凝土界面上会产生滑移。对于短桩来说,滑移的范围可能达到嵌岩段顶部。因此,在对桩身的压缩变形进行计算时,必须考虑这一特性。根据现场及室内试验结果,对目前采用的桩身变形的计算方法提出修正。对比结果表明,所提出的方法能更好地与现场试验的结果相符合,应用所提出的方法可以对载荷试验的结果进行更加准确的判断。

A series of filed load tests and laboratory tests are conducted to investigate the pile deformation and the load transfer behavior of socketed H-shaped steel piles. The instrumented test results reveal that significant shaft resistance can be mobilized along the steel-grout interface. On the other hand, the H-shapes steel pile and the grout body cannot be assumed as a composite body in the evaluation of pile deformation. Laboratory bond tests are carried out on H-shaped steel/grout pile specimens. The bond test results indicat that the lateral confinement can significantly improve the bond strength along the steel-grout interface. Furthermore, if lateral confinement is provided, the welded steel studs can also improve the bond strength. Therefore, the steel-grout bond strength is not a constant along the depth in a socketed H-shaped steel pile. The comparison between the laboratory and the field test results demonstrate that slippage can occur along the steel-grout interface in the load tests. For short piles, the slippage can develop along the whole length above the socket section. For longer piles, slippage is likely to develop to a certain depth above the socket section. Such behaviors should be considered in the evaluation of the pile deformation under the vertical load. A modified calculation method for pile deformation is suggested. The pile deformation evaluated from the suggested method is closer to the field measured data than that the one from the local guidelines. In addition, more detailed analyses can be carried out for load test results by using the suggested method.