低应变同条件下桩型实测波速差异大研究探讨

Study on the Big Difference of Measured Wave Velocity Under the Same Condition by Low Strain Integrity Testing

在工程实践中,有时会出现在设计强度、成桩工艺、养护条件以及龄期相同的桩型,实测低应变波速差异大的情况。这一现象不符合同条件下的桩型,实测波速在某一范围内分布这个常规认知。甚至曾经有过相关专家以实测波速偏差过大为由,质疑检测数据的真实性。通过研究发现,这个波速差异大,并不是检测数据不真实导致的,也不是同条件下的桩型这一条件不满足,更不是同条件下的桩型实测波速在某一范围内这个常规认知不对,而是因为横向尺寸效应引起的。横向尺寸效应能够引起基桩实测波速产生差异,在桩径较大,桩长较短的时候,尤其明显。论本结合实例,对横向尺寸效应影响低应变实测波速进行了分析。

In engineering practice,there will sometimes show with big differences in measured low-strain wave velocity for piles which is under the same design strength,piling process,curing condition and age.This phenomenon is inconsistent with the conventional understanding that the measured pile wave velocity under contract conditions is distributed in a certain range.Even some relevant experts questioned on the authenticity of the detection data because that the measured wave velocity deviation is too large.Through research,the author found that the big difference of wave velocity is not caused by the unreal measured data,and also not caused by the unsatisfied condition of pile under the same conditions,and even not caused by the wrong conventional cognition that the measured wave velocity of pile is within a certain range under the same conditions,but caused by the transverse size effect.The transverse size effect can cause the difference of measured wave velocity of foundation piles,especially when the pile diameter is larger and the pile length is shorter.In this paper,we have analyzed the effect of transverse size effect combined with examples on measured wave velocity under Low strain integrity testing.