小钻孔灌注桩的试验研究

实践证明,钻孔灌注钢筋混凝土桩（灌注桩）是一种较理想的水闸基础。但由于灌注桩在我国应用的历史较短,其计算方法还不够完善,故在一些重大的工程中不得不进行现场试验确定灌注桩基的承载能力。水闸桩基均为群桩,桩数多,承载力大,做现场原型群桩试验困难较大,故一般是做现场单桩试验,然后用单桩资料推求群桩承载能力。大家知道,单桩和群桩在结构和工作机理方面差异较大,两者的可比条件不充分。单桩资料不能较准确地反映群桩承载能力和工作状态,特别是桩距变化时,这种情况更明显。为克服群桩试验的困难,我们进行了小钻孔灌注桩试验,用小桩对单桩、双桩、群桩进行了研究。在试验的基础上,我们建议将现行的单、群桩关系,改为双、群桩关系。

The Test and Research of Small Bored Cast-in-situ piles

Through practice, it is proved that the bored reinforced concrete cast-in-situ pile （cast-in-situ pile） foundation is one of the very ideal form of sluice foundation. The construction of the pile and the calculation method used for the cast-in-situ are still not perfect, because for a short time the cast-in-situ pile is used. So we have to do some necessary pile foundation tests when we are making some important projects. It is only through such tests that we can determine the bearing capacity of the cast-in-situ pile foundation more reasonable and more reliable. But it is very difficult to do such tests, because sluice foundation has a large number of piles, a big body of pile group and a large bearing capacity. It is generally to do a single pile test and then use the data obtained from this test to determine the bearing capacity of pile group. It is well known that the construction and the mechanism are quite different between single pile and pile group. They can't be compared. So the data obtained from the single pile tests are not the reflection of that from pile group, especially when the pile spacing is varied. In order to overcome the difficulty of pile group tests,we carried out the small bored cast-in-situ pile tests, and studied the characters of single pile, two-pile and pile group. The relationship between two-pile and pile group to take the place of the relationship between single pile and pile group is recommended.