Quantitative Investigation of Tomographic Effects in Abnormal Regions of Complex Structures

The detection of abnormal regions in complex structures is one of the most challenging targets for under-ground space engineering. Natural or artificial geologic variations reduce the effectiveness of conventional exploration methods. With the emergence of real-time monitoring, seismic wave velocity tomography allows the detection and imaging of abnormal regions to be accurate, intuitive, and quantitative. Since tomographic results are affected by multiple factors in practical small-scale applications, it is necessary to quantitatively investigate those influences. We adopted an improved three-dimensional (3D) tomography method combining passive acoustic emission acquisition and active ultrasonic measurements. By varying individual parameters (i.e., prior model, sensor configuration, ray coverage, event distributions, and event location errors), 37 comparative tests were conducted. The quantitative impact of different factors was obtained. Synthetic experiments showed that the method could effectively adapt to complex structures. The optimal input parameters based on quantization results can significantly improve the detection reliability in abnormal regions. (C) 2020 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company.

Automated summary

Detecting abnormal regions in complex structures in underground space engineering is a challenging task. By utilizing an improved 3D tomography method and combining passive acoustic emission acquisition with active ultrasonic measurements, it is possible to accurately and quantitatively identify and image abnormal regions, thereby improving detection reliability.