Zhang Yunpeng, El Naggar M Hesham, Wu Wenbing, Wang Zongqin
Faculty of Engineering, China University of Geosciences, Wuhan 430074, China.
Geotechnical Research Centre, Department of Civil and Environmental Engineering, Western University, London, ON N6A 5B9, Canada.
Sensors (Basel). 2022 Jul 16;22(14):5330. doi: 10.3390/s22145330.
Low-strain tests are widely utilized as a nondestructive approach to assess the integrity of newly piled foundations. So far, the examination of existing pile foundations is becoming an indispensable protocol for pile recycling or post-disaster safety assessment. However, the present low-strain test is not capable of testing existing pile foundations. In this paper, the torsional low-strain test (TLST) is proposed to overcome this drawback. Both the upward and downward waves are considered in the TLST wave propagation model established in this paper so that a firm theoretical basis is grounded for the test signal interpretations. A concise semi-analytical solution is derived and its rationality is verified by comparisons with the existing solutions for newly piled foundations and the finite element results. The main conclusions of this study can be drawn as follows: (1). by placing the sensors where the incident wave is applied, the number of reflected signals can be minimized; (2). the defects can be more evidently identified if the incident wave/sensors are input/installed close to the superstructure/pile head.
低应变测试作为一种无损检测方法被广泛应用于评估新建桩基础的完整性。到目前为止，对既有桩基础的检测正成为桩回收利用或灾后安全评估中不可或缺的环节。然而，目前的低应变测试无法对既有桩基础进行检测。本文提出了扭转低应变测试（TLST）以克服这一缺点。本文建立的TLST波传播模型中同时考虑了上行波和下行波，从而为测试信号解释奠定了坚实的理论基础。推导了一个简洁的半解析解，并通过与新建桩基础的现有解及有限元结果进行比较验证了其合理性。本研究的主要结论如下：（1）将传感器置于施加入射波的位置，可使反射信号数量最小化；（2）如果入射波/传感器靠近上部结构/桩头输入/安装，缺陷能够更明显地被识别。
