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Open AccessArticle

Field Validation of a Magnetic Sensor to Monitor Borehole Deviation during Tunnel Excavation

1
State Key Laboratory of Coastal and Offshore Engineering, School of Civil Engineering, Dalian University of Technology, Dalian 116024, China
2
Henan Tianchi Pumped Storage Energy Corporation, Nanyang 474664, China
3
Holcombe Department of Electrical and Computer Engineering, Clemson University, Clemson, SC 29634, USA
*
Authors to whom correspondence should be addressed.
Materials 2018, 11(9), 1511; https://doi.org/10.3390/ma11091511
Received: 26 July 2018 / Revised: 13 August 2018 / Accepted: 16 August 2018 / Published: 23 August 2018
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
In this article, a magnetic sensor is proposed to monitor borehole deviation during tunnel excavation. It is made by piling four super-strong N42 NdFeB cylinder magnets and then encasing them in an aluminum alloy hollow cylinder. The distribution of the magnetic field produced by the magnetic sensor and its summation with the geomagnetic field (GMF) in a global coordinate system are derived based on the theory of magnetic fields. An algorithm is developed to localize the position of the magnetic sensor. The effect of the GMF variation on the effective monitoring range of the magnetic sensor is also studied numerically. Field validation tests are conducted at Jinzhai Pumped-Storage hydroelectric power station, during the excavation of an inclined tunnel in Anhui Province of China. Test results show that the algorithm and the magnetic sensor are used successfully to detect the deviation of the borehole with an estimated error of approximately 0.5 m. The errors are mainly from the measurement errors of the coordinates, of both the test and the measurement points. The effective monitoring range of the magnetic sensor is dependent on the direction of the magnetic sensor as well as the variation of the GMF. View Full-Text
Keywords: magnetic sensor; pumped-storage hydroelectricity; tunnel excavation; borehole deviation magnetic sensor; pumped-storage hydroelectricity; tunnel excavation; borehole deviation
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MDPI and ACS Style

Tang, F.; Yang, J.; Li, H.-N.; Liu, F.; Wang, N.; Jia, P.; Chen, Y. Field Validation of a Magnetic Sensor to Monitor Borehole Deviation during Tunnel Excavation. Materials 2018, 11, 1511.

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