title: Impedance-Based Pre-Stress Monitoring of Rock Bolts Using a Piezoceramic-Based Smart Washer-A Feasibility Study.
abstract: Pre-stress degradation or looseness of rock bolts in mining or tunnel engineering threatens the stability and reliability of the structures. In this paper, an innovative piezoelectric device named a "smart washer" with the impedance method is proposed with the aim of developing a real-time device to monitor the pre-stress level of rock bolts. The proposed method was verified through tests on a rock bolt specimen. By applying high-frequency sweep excitations (typically >30 kHz) to the smart washer that was installed on the rock bolt specimen, we observed that the variation in impedance signatures indicated the rock bolt pre-stress status. With the degradation of rock bolt pre-stress, the frequency in the dominating peak of the real part of the electrical impedance signature increased. To quantify the effectiveness of the proposed technique, a normalized root mean square deviation (RMSD) index was developed to evaluate the degradation level of the rock bolt pre-stress. The experimental results demonstrated that the normalized RMSD-based looseness index, which was computed from the impedance value detected by the "smart washer", increased with loss of the pre-stress of the rock bolt. Therefore, the proposed method can effectively detect the degradation of rock bolt pre-stress, as demonstrated by experiments.
authors.affiliation: Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China;. ahbowang@home.swjtu.edu.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;. lshuo@dlut.edu.cn.
authors.forename: Linsheng
authors.initials: L
authors.lastname: Huo
authors.affiliation: State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;. chendongjt@163.com.
authors.forename: Dongdong
authors.initials: D
authors.lastname: Chen
authors.affiliation: Smart Material and Structure Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA;. wli27@uh.edu.
authors.forename: Weijie
authors.initials: W
authors.lastname: Li
authors.affiliation: Smart Material and Structure Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA;. gsong@uh.edu.
authors.forename: Gangbing
authors.initials: G
authors.lastname: Song
keywords: electro-mechanical impedance; piezoceramic materials; pre-stress level monitoring; rock bolt monitoring; smart washer