{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,9]],"date-time":"2026-07-09T04:22:18Z","timestamp":1783570938526,"version":"3.55.0"},"reference-count":31,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2017,1,27]],"date-time":"2017-01-27T00:00:00Z","timestamp":1485475200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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 \u201csmart washer\u201d 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 &gt;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 \u201csmart washer\u201d, 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.<\/jats:p>","DOI":"10.3390\/s17020250","type":"journal-article","created":{"date-parts":[[2017,1,27]],"date-time":"2017-01-27T11:23:02Z","timestamp":1485516182000},"page":"250","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":77,"title":["Impedance-Based Pre-Stress Monitoring of Rock Bolts Using a Piezoceramic-Based Smart Washer\u2014A Feasibility Study"],"prefix":"10.3390","volume":"17","author":[{"given":"Bo","family":"Wang","sequence":"first","affiliation":[{"name":"Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3044-2630","authenticated-orcid":false,"given":"Linsheng","family":"Huo","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dongdong","family":"Chen","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weijie","family":"Li","sequence":"additional","affiliation":[{"name":"Smart Material and Structure Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA;"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5135-5555","authenticated-orcid":false,"given":"Gangbing","family":"Song","sequence":"additional","affiliation":[{"name":"Smart Material and Structure Laboratory, Department of Mechanical Engineering, University of Houston, Houston, TX 77204, USA;"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2017,1,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"280","DOI":"10.1016\/j.egypro.2011.12.930","article-title":"The design and application of rock bolting in coal mine","volume":"14","author":"Qian","year":"2012","journal-title":"Energy Procedia"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"633","DOI":"10.1016\/0148-9062(95)00021-8","article-title":"Laboratory evaluation of cement-based grouts and grouted rock anchors","volume":"32","author":"Benmokrane","year":"1995","journal-title":"Int. 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