桩顶-孔内双测点完整性检测理论及缺陷多维度分析

Pile top-in hole two points coupled integrity test theory and multiple dimensions analysis of defect

提出一种利用放置于桩顶及桩孔内(如声测管等)的传感器同步接收动力响应信号的桩基完整性检测新方法;建立变截面声阻抗一维杆件模型,通过有限元分析(FEA)验证该方法的可行性;利用验证后的模型解和解析解对缺陷长度、深度和程度进行多维度分析。研究结果表明:通过分析传感器同步接收到的动力响应信号,本文所提方法能够应用于超长桩、多缺陷桩及桩身缺陷量化等复杂工况。由于多解性的存在,当缺陷程度较轻或缺陷长度较短时,本方法难以精确测量缺陷高度;然而,当缺陷高度较大时,偏离度D及偏离值F与缺陷高度无关,仅与缺陷程度有关,因此,对于长度较深(大于1 m)、缺陷程度较严重(大于20%)的缺陷,本文所提模型及检测理论可对桩身缺陷进行定位及量化。

A new method for the pile integrity test(PIT)was proposed by installing two transducers at the pile top and inside the pile foundation and collecting dynamic responses simultaneously.A continuous rod model with various cross-sectional impedance was developed,and the feasibility of the proposed method was verified by arigorous finite element analysis(FEA).The verified model solution and the analytical solution were employed to evaluate multiple dimensions of the defect incorporating length,depth and defect degree.The results show that by recording the time and amplitude of the crest of incident waves collected inside the pile from the top to bottom,the developed method can be applied in complicated conditions such as super-long piles,piles with various defects and quantification of pile defect.It is impractical to determine the length of defect precisely as the defect degree is relatively low or its length is relatively short because of the multiple solutions.However,the divergence values D and F are related to the defect degree only as the defect length is relatively long.Thus,for a relatively longer(longer than 1 m)defect with higher degree(larger than 20%),the pile defect can be positioned and quantified by the proposed method and its test theory.