New LGFBG-Based Structural Integrity Evaluation Method for Cement-Grouted Soil Nails
Publication: International Journal of Geomechanics
Volume 17, Issue 8
Abstract
This paper proposes a novel optical fiber sensor-based nondestructive method, namely, the long-gauge fiber Bragg grating (LGFBG) method, for integrity assessment of cement-grouted soil nails. This LGFBG sensor was developed by encapsulating a number of straight, bare FBG sensors inside an aluminum tube, and then mounting them on a steel bar surface for monitoring average strain distributions of soil nails subjected to tension force. Measured strain distributions of LGFBG sensors were finally used for the prediction of effective elastic modulus (EEM) distributions along the soil nails and the assessment of soil nail integrity in terms of the predicted EEM. A number of pullout tests of soil nails with different defects in the laboratory were performed to verify the feasibility of this proposed method. Pullout test results indicate that the elongation contributions of defective soil nail sections are 1.5 to 3 times the intact soil nail sections, whereas the related EEM values of the two defective soil nail sections are around 0.3 to 0.5 times that of intact soil nail sections. The statistical hypothesis Student’s t-test was used to determine the magnitude ranges of the modulus ratio leading to a rejection of the null hypothesis for a prespecified level of significance. In this study, a significance level of 0.01% is suggested for the integrity evaluation of cement-grouted soil nails.
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Acknowledgments
The authors wish to thank the National Natural Science Foundation of China (Project 41602352); the State Key Laboratory of Earthquake Dynamics; the Institute of Geology; the China Earthquake Administration (Project LED2013B01); and the Key Laboratory of Structure and Wind Tunnel of Guangdong Higher Education Institutes, Shantou, China (Project 201603) for their financial support. The authors also wish to thank the Fundamental Research Funds for the Central Universities (Projects 15D110136 and 15D110153) for its financial support.
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Information & Authors
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Published In
International Journal of Geomechanics
Volume 17 • Issue 8 • August 2017
Copyright
© 2017 American Society of Civil Engineers.
History
Received: Jul 5, 2016
Accepted: Dec 20, 2016
Published online: Feb 27, 2017
Discussion open until: Jul 27, 2017
Published in print: Aug 1, 2017
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