Nongrouted Ratio Evaluation of Rock Bolts by Reflection of Guided Ultrasonic Waves

Yu, Jung-Doung; Bae, Myeong Ho; Lee, In Mo; Lee, Jong Sub

doi:10.1061/(asce)gt.1943-5606.0000767

Cited by 37 publications

(16 citation statements)

References 12 publications

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“…There have been efforts aiming to inspect rockbolt grouting conditions using relatively low frequency ultrasonic waves, mostly in the order of several tens of kHz. Diagnostic acoustic waves are either generated with an ultrasound transducer or with help of an impact hammer (Fishman 2004(Fishman , 2005Zou et al 2010;Yu et al 2013). Applications of MHz frequency ultrasound to inspection of rockbolt integrity have been investigated, mainly on theoretical aspects of guided ultrasonic waves in rockbolts (Beard et al 2002(Beard et al , 2003Wu et al 2007).…”

Section: Introductionmentioning

confidence: 99%

A new paradigm in ground support monitoring through ultrasonic monitoring of clusters of rockbolts

Sun¹,

Wu²,

Kruger³

et al. 2019

Proceedings of the Ninth International Symposium on Ground Support in Mining and Underground Construction

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In most of today's underground mines, ground support monitoring is mainly conducted through using microseismic sensors, LiDAR, extensometers, cameras, or visual inspection. These monitoring tools are complementary in nature. Due to high costs associated with purchase, installation, maintenance and utilisation, they are usually deployed or used at sparsely selected critical locations, some of them on a non-continuous basis. This means that some important pieces of information on ground support conditions may be missing either location-wise or time-wise. In the last four years, the Energy, Mining and Environment Research Centre of the National Research Council Canada (NRC), in collaboration with CanmetMINING of Natural Resources Canada (NRCan), has developed next generation ultrasound rockbolt sensors (RBS TM) for monitoring load change and deformation experienced by rockbolts. Intrinsically low costing and installation onto exposed end of rockbolts using production bolters, the technology is meant to be deployed on a large number of rockbolts whereby the instrumented rockbolts become a network of ground condition sensors to provide on-demand 3D mapping of ground stress change and deformation all over excavated zones. Field trial data collected in a production mine has demonstrated that monitoring a cluster of rockbolts can provide much more meaningful and reliable information about ground condition when compared with information provided by a single instrumented rockbolt. Therefore, monitoring clusters of rockbolts is recommended as being an effective practice for ground support monitoring.

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Section: Introductionmentioning

confidence: 99%

A new paradigm in ground support monitoring through ultrasonic monitoring of clusters of rockbolts

Sun¹,

Wu²,

Kruger³

et al. 2019

Proceedings of the Ninth International Symposium on Ground Support in Mining and Underground Construction

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show abstract

“…A research group from Dalhousie University, Canada, consecutively investigated the influence of curing time [ 10 ], grouted length [ 11 ], grout strength [ 12 ], and missing grout [ 13 ] on the characteristics of ultrasonic guided waves on the grouted rock bolt. Another research group from the Republic of Korea also systematically conducted experiments and field tests on the rock bolt integrity monitoring using ultrasonic guided waves [ 14 , 15 , 16 ]. The wavelet transform was adopted to extract useful information on the grouting conditions of the rock bolt.…”

Section: Introductionmentioning

confidence: 99%

Impedance-Based Pre-Stress Monitoring of Rock Bolts Using a Piezoceramic-Based Smart Washer—A Feasibility Study

Wang

Huo

Chen

et al. 2017

Sensors

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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.

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“…The study of using an ultrasonic guided wave method for non-destructive evaluation of rock bolts has been researched [1,2,3,4,5,6,7,8,9,10,11]. In recent years, the stress wave reflection method has emerged as a promising non-destructive evaluation technique for rock bolts condition assessment [12,13,14].…”

Section: Introductionmentioning

confidence: 99%

“…The transducer used for stress wave generation has great influence on the quality of the acquired signals. To date, lead zirconate titanate (PZT) elements and hammer impacts are the traditional methods to excite stress wave in a rock bolt [6,10]. These methods show their limitations when it comes to practical application.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the Length of Installed Rock Bolt Based on Stress Wave Reflection by Using a Giant Magnetostrictive (GMS) Actuator and a PZT Sensor

Luo

Wang

et al. 2017

Sensors

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Rock bolts, as a type of reinforcing element, are widely adopted in underground excavations and civil engineering structures. Given the importance of rock bolts, the research outlined in this paper attempts to develop a portable non-destructive evaluation method for assessing the length of installed rock bolts for inspection purposes. Traditionally, piezoelectric elements or hammer impacts were used to perform non-destructive evaluation of rock bolts. However, such methods suffered from many major issues, such as the weak energy generated and the requirement for permanent installation for piezoelectric elements, and the inconsistency of wave generation for hammer impact. In this paper, we proposed a portable device for the non-destructive evaluation of rock bolt conditions based on a giant magnetostrictive (GMS) actuator. The GMS actuator generates enough energy to ensure multiple reflections of the stress waves along the rock bolt and a lead zirconate titantate (PZT) sensor is used to detect the reflected waves. A new integrated procedure that involves correlation analysis, wavelet denoising, and Hilbert transform was proposed to process the multiple reflection signals to determine the length of an installed rock bolt. The experimental results from a lab test and field tests showed that, by analyzing the instant phase of the periodic reflections of the stress wave generated by the GMS transducer, the length of an embedded rock bolt can be accurately determined.

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Nongrouted Ratio Evaluation of Rock Bolts by Reflection of Guided Ultrasonic Waves

Cited by 37 publications

References 12 publications

A new paradigm in ground support monitoring through ultrasonic monitoring of clusters of rockbolts

A new paradigm in ground support monitoring through ultrasonic monitoring of clusters of rockbolts

Impedance-Based Pre-Stress Monitoring of Rock Bolts Using a Piezoceramic-Based Smart Washer—A Feasibility Study

Measurement of the Length of Installed Rock Bolt Based on Stress Wave Reflection by Using a Giant Magnetostrictive (GMS) Actuator and a PZT Sensor

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