application of ground penetrating radar in dam body detection

Procedia Engineering Available online at www.sciencedirect.com Procedia Engineering 00 (2011) 000–000 Procedia Engineering 26 (2011) 1820 – 1826 www.elsevier.com/locate/procedia First International Symposium on Mine Safety Science and Engineering Application of Ground Penetrating Radar in Dam body detection Li Huia,b Ma Haitaob a* a Civil & Environment Engineering School, University of Science & Technology Beijing,Beijing 100083,C hina b Institute of Mine safety Technology,China Academy of Safety Science&Technology, Beijing 100012, China Abstract The basic principle, the detection methods, data processing, interpretation method and the application of ground penetrating radar in the dam body detection were introduced and the problems aroused during application were primarily studied The cause of the dam leakage was very complicated and through geophysical prospecting the reasons for the dam leakage and relevant reinforcement measures can be provided The leakage parts will appear to be electromagnetic abnormal due to the changes of the water content, which will be an advantage in the application of geological radar method The dam body was detected using Ground penetrating radar detection technology and the quality of the dam project were analyzed combining with geological conditions, practical situation of the project and the characteristics of the radar images The location of the crack fracture zone in the dam was predicted and feasible technological measures were put forward © 2011 Published by Elsevier Ltd Selection and/or peer-review under responsibility of China Academy of Safety Science and Technology, China University of Mining and Technology(Beijing), McGill University and University of Wollongong Keywords: Ground Penetrating Radar, reservoir dam body,hidden danger detection,spottiness feature Introduction After the completion of the dam, hidden problems will often occur with the increase of service years, which can easily lead to leakage or even break of the dam [1].To eliminate the hidden risk in dams, a variety of geophysical methods were used to detect them by many academicians both at home and abroad, trying to determine the factors causing the risks [2,3] Ground penetrating radar has become a powerful tool in geophysical exploration with its high resolution and detection efficiency [4] With the development of signal processing and electronic technology and the continuous accumulation of practical operating * Corresponding author Tel.: +8615210605208; E-mail address: lhui119@163.com 1877-7058 © 2011 Published by Elsevier Ltd doi:10.1016/j.proeng.2011.11.2372 1821 Li Hui and Ma Haitao / Procedia – 1826 Li Hui/ ProcediaEngineering Engineering26 00(2011) (2011)1820 000–000 experience, ground penetrating radar technology progresses ceaselessly, and its range of applications expands It has been applied in numerous fields such as rocky soil investigation, building Structures investigations, project quality NDT, hydro-geological surveys, ecological environment protection and so on[5,6] Detection principle Ground penetrating radar detection is an electromagnetic technology which uses high frequency electromagnetic wave in the form of a wideband short-pulse to scan the distribution of the underground medium and non-visible objects or underground interfaces It determines the internal structure of underground medium or the location of invisible object through analyzing the time-frequency and amplitude characteristics of reflected electromagnetic waves [7] The working principle is as follows: high-frequency electromagnetic waves were transmitted in wideband pulses form through the antenna, reflected or transmitted by the object, and then captured by the receiving antenna High frequency electromagnetic waves in the form of a wideband short-pulse were transmitted through ground penetrating radar On the ground they were sent to the underground through antenna T, reflected by the underground formation or object, and then received by the other antenna R Pulse waves travel time can be shown as that equation below: (4 z  x ) t v (1) In the equation: t is used to represent electromagnetic wave two-way travel time; z is used to represent the depth of the reflector; x is the distance between transmitting and receiving antenna; v is the velocity of electromagnetic wave in the underground medium; propagation velocity v can be analyzed and determinated according to the available data, or be calculated by the equation below:    v                       (2) In the equation: μ represents permeability; ε is dielectric constant; σ is conductivity; ω is angular frequency of electromagnetic wave Rock and soil, which generally is nonmagnetic and nonconductive medium, satisfy σ/ωε