The Experts below are selected from a list of 4596 Experts worldwide ranked by ideXlab platform
Andrej Atrens - One of the best experts on this subject based on the ideXlab platform.
-
5178 - METALLURGICAL ASPECTS OF Rock Bolt ENVIRONMENT FRACTURE
2020Co-Authors: Erwin Gamboa, Ernesto Villalba, Andrej AtrensAbstract:The aim of this research was to understand the Stress Corrosion Cracking (SCC) of Rock Bolts. The laboratory tests have produced fracture surfaces similar to those from service. The experimental study elucidated the environmental condition leading to Rock Bolt SCC, and was used to determine the threshold stress and the threshold potential. A hydrogen embrittlement mechanism is proposed.
-
Hydrogen embrittlement and Rock Bolt stress corrosion cracking
Engineering Failure Analysis, 2009Co-Authors: Ernesto Villalba, Andrej AtrensAbstract:This paper considers our recent research on Rock Bolt stress corrosion cracking (SCC) which studied the influence of metallurgy using a range of (1) existing Rock Bolt steels and (2) commercial steels. The chemical composition, mechanical properties and microstructures of these steels varied considerably. The aim is to understand this failure mechanism and in particular to apply the knowledge gained from the study of SCC and hydrogen embrittlement (HE) of steels. The resistance of 1008, X65, X70 and 4145H to SCC/HE was similar, an effect which could be hardly expected as these steels have different strengths, microstructures and H-trap distributions. Different steel microstructures (pearlitic-ferritic and tempered martensite) had similar resistance to SCC and HE in the most aggressive conditions (pH 2.1 and -1500 mVSCE) and had the same dimple rupture fracture surface. © 2008 Elsevier Ltd. All rights reserved.
-
hydrogen embrittlement and Rock Bolt stress corrosion cracking
Engineering Failure Analysis, 2009Co-Authors: Ernesto Villalba, Andrej AtrensAbstract:Abstract This paper considers our recent research on Rock Bolt stress corrosion cracking (SCC) which studied the influence of metallurgy using a range of (1) existing Rock Bolt steels and (2) commercial steels. The chemical composition, mechanical properties and microstructures of these steels varied considerably. The aim is to understand this failure mechanism and in particular to apply the knowledge gained from the study of SCC and hydrogen embrittlement (HE) of steels. The resistance of 1008, X65, X70 and 4145H to SCC/HE was similar, an effect which could be hardly expected as these steels have different strengths, microstructures and H-trap distributions. Different steel microstructures (pearlitic–ferritic and tempered martensite) had similar resistance to SCC and HE in the most aggressive conditions (pH 2.1 and −1500 mV SCE ) and had the same dimple rupture fracture surface.
-
metallurgical aspects of Rock Bolt stress corrosion cracking
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Ernesto Villalba, Andrej AtrensAbstract:Abstract This paper reports on the metallurgical influence on Rock Bolt stress corrosion cracking for a range of: (1) existing Rock Bolt steels and (2) commercial steels. Rock Bolt steels 1355, MAC and MA840B displayed SCC when loaded at 0.019 MPa s −1 in the sulphate pH 2.1 solutions at the free corrosion potential. They had comparable threshold stresses and comparable stress corrosion crack velocities. Rock Bolts steel 5152CW10D had the best SCC resistance of the Rock Bolt steels tested. Cold work increased the resistance of 5152 to SCC. The five commercial steels 1008, X65, X70, 4140 and 4145H were subjected to the linearly increasing stress test (LIST) in the dilute pH 2.1 sulphate solution at their free corrosion potential and at increasingly negative applied potential values to −1500 mV. The increasingly negative applied potential increases the aggressivity of SCC conditions because of increasing hydrogen liberated at the specimen surface. The steels 1008, X65, X70 and 4145H resisted SCC for all applied potentials including −1500 mV.
-
an evaluation of steels subjected to Rock Bolt scc conditions
Engineering Failure Analysis, 2007Co-Authors: Ernesto Villalba, Andrej AtrensAbstract:Abstract In order to understand the metallurgical influences on Rock Bolt stress corrosion cracking (SCC), an evaluation has been carried out of a range of steels subjected to the conditions previously identified as producing laboratory SCC similar to that observed for Rock Bolts in service. The approach has been to use the linearly increasing stress test for samples exposed to a dilute pH 2.1-sulphate solution, as per our prior studies. SCC was evaluated from the decrease in tensile strength, ductility and fractography as revealed by scanning electron microscopy observation. A range of SCC susceptibilities was observed.
Gangbing Song - One of the best experts on this subject based on the ideXlab platform.
-
monitoring of pre load on Rock Bolt using piezoceramic transducer enabled time reversal method
Sensors, 2017Co-Authors: Bo Wang, Dongdong Chen, Gangbing SongAbstract:Rock Bolts ensure structural stability for tunnels and many other underground structures. The pre-load on a Rock Bolt plays an important role in the structural reinforcement and it is vital to monitor the pre-load status of Rock Bolts. In this paper, a Rock Bolt pre-load monitoring method based on the piezoceramic enabled time reversal method is proposed. A lead zirconate titanate (PZT) patch transducer, which works as an actuator to generate stress waves, is bonded onto the anchor plate of the Rock Bolt. A smart washer, which is fabricated by sandwiching a PZT patch between two metal rings, is installed between the hex nut and the anchor plate along the Rock Bolt. The smart washer functions as a sensor to detect the stress wave. With the increase of the pre-load values on the Rock Bolt, the effective contact surface area between the smart washer and the anchor plate, benefiting the stress wave propagation crossing the contact surface. With the help of time reversal technique, experimental results reveal that the magnitude of focused signal clearly increases with the increase of the pre-load on a Rock Bolt before the saturation which happens beyond a relatively high value of the pre-load. The proposed method provides an innovative and real time means to monitor the pre-load level of a Rock Bolt. By employing this method, the pre-load degradation process on a Rock Bolt can be clearly monitored. Please note that, currently, the proposed method applies to only new Rock Bolts, on which it is possible to install the PZT smart washer.
-
a load measuring anchor plate for Rock Bolt using fiber optic sensor
Smart Materials and Structures, 2017Co-Authors: Siu Chun Michael Ho, Bo Wang, Weijie Li, Gangbing SongAbstract:Rock Bolts are the devices that used to reinforce the Rock masses in mining tunnels and underground excavation structures. The loading level of the Rock Bolt indicates the reinforcing efficiency and is able to ensure safe underground operation by giving warnings to the underground miners prior to any accidents. Therefore, it is very important to monitor the load level of the Rock Bolts. In this short communication, we propose a smart anchor plate, a simple but effective device that uses fiber Bragg gratings (FBG) type optic sensor, to monitor the load level of the Rock Bolt. Instead of measuring the stress/strain on the Rock Bolt, which adds more complexity, the proposed method monitors the Rock Bolt load by measuring the load experience on the Rock Bolt anchor plate. Such a configuration has the advantages of simple structure and flexible implementation. In experimental observation, the FBG instrumented anchor plate is able to observe the load of the plate with good repeatability. This test will lead to further in-depth studies involving finite element analysis as well as more complex applications.
-
a review of Rock Bolt monitoring using smart sensors
Sensors, 2017Co-Authors: Gangbing Song, Weijie Li, Bo Wang, Siu Chun Michael HoAbstract:Rock Bolts have been widely used as Rock reinforcing members in underground coal mine roadways and tunnels. Failures of Rock Bolts occur as a result of overloading, corrosion, seismic burst and bad grouting, leading to catastrophic economic and personnel losses. Monitoring the health condition of the Rock Bolts plays an important role in ensuring the safe operation of underground mines. This work presents a brief introduction on the types of Rock Bolts followed by a comprehensive review of Rock Bolt monitoring using smart sensors. Smart sensors that are used to assess Rock Bolt integrity are reviewed to provide a firm perception of the application of smart sensors for enhanced performance and reliability of Rock Bolts. The most widely used smart sensors for Rock Bolt monitoring are the piezoelectric sensors and the fiber optic sensors. The methodologies and principles of these smart sensors are reviewed from the point of view of Rock Bolt integrity monitoring. The applications of smart sensors in monitoring the critical status of Rock Bolts, such as the axial force, corrosion occurrence, grout quality and resin delamination, are highlighted. In addition, several prototypes or commercially available smart Rock Bolt devices are also introduced.
-
measurement of the length of installed Rock Bolt based on stress wave reflection by using a giant magnetostrictive gms actuator and a pzt sensor
Sensors, 2017Co-Authors: Weijie Li, Bo Wang, Qingqing Fu, Gangbing SongAbstract: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.
Yujing Jiang - One of the best experts on this subject based on the ideXlab platform.
-
performance of a new yielding Rock Bolt under pull and shear loading conditions
Rock Mechanics and Rock Engineering, 2019Co-Authors: Xuezhen Wu, Yujing Jiang, Gang Wang, Bin Gong, Zhenchang Guan, Tao DengAbstract:High stress in surrounding Rock mass could cause serious stability problems such as larger squeezing deformation in soft Rock and Rock burst in hard Rock. The support system applied in high in situ stress conditions should be able to carry high load and accommodate large deformation of Rock mass. This paper presented a new yielding Rock Bolt, called tension and compression-coupled yielding Rock Bolt, which is promising to provide support for both squeezing and burst-prone Rock mass encountered in mining or tunneling at depth. The new Bolt mainly consists of a steel rod and two additional anchors. The steel rod is a round shape bar with varying surface conditions. The inner segment is processed into rough surface, while the middle segment of the rod has smooth surface. Two additional anchors were arranged on both ends of smooth segment. The Bolt is fully encapsulated in a borehole with either cement or resin grout. The rough segment and the inner anchor are firmly fixed in the bottom of the borehole, while the smooth segment has no or very weak bonding to the grout, which can stretch to accommodate Rock dilatation. First, direct quasi-static pull tests were performed to examine the load capacity of tension and compression-coupled anchor. The results showed that the coupling action of tension to the rough rod and compression on the inner additional anchor by grout in different positions can increase the ultimate bearing capacity of inner anchoring segment significantly. Second, the performance of the new Bolt and the fully encapsulated rebar Bolt was tested under fracture opening condition. Results showed that the load and strain concentration could result in premature failure of fully encapsulated rebar Bolt. However, the smooth segment of TCC Yielding Rock Bolt can detach from the grout under pull loading and provide a larger deformation to accommodate Rock dilations. Third, shear tests were performed to examine the deformation mechanism of the new Rock Bolt under fracture sliding condition. Results showed that the smooth section of the new Bolt specimen can deform freely to accommodate the sliding of fracture. The maximum shear displacement of the new Bolt specimen is much larger than the fully encapsulated rebar Bolt specimen, which is promising a better ability to accommodate the large displacement sliding of fracture in engineering practice.
-
behaviour of Rock joint reinforced by energy absorbing Rock Bolt under cyclic shear loading condition
International Journal of Rock Mechanics and Mining Sciences, 2018Co-Authors: Xuezhen Wu, Yujing Jiang, Bin Gong, Tao Deng, Zhenchang GuanAbstract:Abstract Rock joints will undergo a sequence of cyclic shearing loadings during a seismic event. However, the effect of cyclic shear loading on the energy-absorbing Rock Bolts has never been studied before. Laboratory shear experiments were carried out to study the shear behaviour of Rock joints reinforced by the energy-absorbing Rock Bolts under cyclic loading condition. The results illustrated that the support effect of the energy-absorbing Rock Bolts was very small after the first cycles in the cyclic shear experiments. In the case of small cyclic distances, the shear resistance of the energy-absorbing Rock Bolts will gradually recover after the shear displacement has exceeded the cyclic distance in the subsequent shear experiment after 5 cycles. In the case of large cyclic distances, no recovery of shear resistance was found in the subsequent shear experiment, indicating that the energy-absorbing Rock Bolts had completely lost its supporting role after cyclic shear loading. A new index of shear energy loss ratio (SELR) was proposed to evaluate the shear behaviour of energy-absorbing Rock Bolt and Rock joint under cyclic shear loading condition. The results showed that the SELR of Rock joints was commonly less than 20%. However, the SELR of Rock Bolts could reach nearly 100% when the cyclic distance was larger than 8 mm. When the cyclic distance was 4 mm or 6 mm, the SELR of the fully encapsulated Rock Bolts almost reached 100%. However, the SELR of the energy-absorbing Rock Bolts were located in the range of 50–80% for the same condition. The results indicated that the shear behaviour of a Rock Bolt inserted in a Rock joint was strongly influenced by cyclic shear loading. The shear performance of the energy-absorbing Rock Bolts was better than the fully encapsulated Rock Bolts under cyclic shear loading conditions.
-
quasi static laboratory testing of a new Rock Bolt for energy absorbing applications
Tunnelling and Underground Space Technology, 2013Co-Authors: Gang Wang, Yujing Jiang, Xuezhen Wu, Na Huang, Shugang WangAbstract:Abstract High stress in the surrounding Rock mass can cause serious stability problems. The applied support system used under high in situ stress condition should be able to carry high loads and also to accommodate large deformation without experiencing serious damage. This paper presents a specifically designed Rock Bolt for energy-absorbing applications, which can provide support for squeezing and burst-prone Rocks often encountered during underground excavation in the tunneling and mining community. The Bolt mainly consists of a smooth steel bar with an anchor near the bottom end of its body. The anchor is firmly fixed within a borehole using either cement grout or resin, while the smooth section of the Bolt inserted in the anchor can slide in response to Rock deformation once the load exceeds the pre-set capability. Static pull tests on the new Bolt show that it can elongate to any expected length at a high load level, thereby absorbing a large amount of energy to maintain the stability of surrounding Rock.
-
an analytical model to predict axial load in grouted Rock Bolt for soft Rock tunnelling
Tunnelling and Underground Space Technology, 2004Co-Authors: Tetsuro Esaki, Yujing JiangAbstract:An analytical model is proposed to predict the axial force of grouted Rock Bolt in the tunnelling design. The interaction mechanism of the Rock Bolt and the soft Rock mass has been described according to their consistent displacement. Coupling and decoupling behaviors of the Rock Bolt around a circular tunnel have been analyzed. According to case studies, the theoretical prediction of the axial force agrees well with the in situ measured results. The installing time and the length of the Rock Bolt, and the deformation modulus of the Rock mass are taken as study parameters to analyze the supporting behavior of the Rock Bolt. According to the results of the theoretical analysis, there are some conclusions as followings: (1) a lower axial force is resulted because of the delay of installing Rock Bolt and its supporting effect may be reduced; (2) the larger displacement is caused by the lower deformation modulus of the Rock mass, and a higher axial force is resulted in the Rock Bolt. If the shear strength of the Rock mass is not enough, the decoupling behavior will take place interior the Rock mass, and the performance of Rock Bolt may be reduced; (3) the position of a neutral point is related with the radius of tunnel, the physical properties of the Rock Bolt and the Rock mass. It is found that the position of the neutral point and the maximum axial force of the Rock Bolt installed in the soft Rock may tend to be constant when its length is long enough, which means that the supporting effect of the Rock Bolt can not be improved significantly only by increasing the length of the Rock Bolt. By using this model, a way is supplied to analyze the supporting behavior of the Rock Bolt, and a method is provided for the quantitative evaluation of its supporting effect in NATM tunnelling.
-
a Rock Bolt and Rock mass interaction model
International Journal of Rock Mechanics and Mining Sciences, 2004Co-Authors: Tetsuro Esaki, Yujing JiangAbstract:Abstract An analytical model for Rock Bolts has been developed based on an improved Shear–Lag Model. The development of the model is based on the description of the interaction behavior of the Rock Bolt, the grout medium and the Rock mass. On the basis of the model, the coupling and decoupling behavior of the Rock Bolt in pullout tests, uniform deformation the Rock mass and intersecting joints are analyzed. The pullout test characteristic is described by the proposed model, and a back analysis method is proposed to calculate the shear strength of the interface media. For the Rock Bolts in a deformed Rock mass, the influence of the installation time of the Rock Bolt has been taken into account, and the theoretical prediction is verified by the measured data. According to the proposed model, the position of the neutral point is not only related to the length of the Rock Bolt and the radius of a tunnel, but also is strongly influenced by the mechanical properties of the Rock mass. Analysis of the joints intersecting the Rock Bolt shows that there may be more than one neutral point on the Rock Bolt, and the prediction of the simplified model is consistent with the pullout model. By using this model, a method is proposed to analyze the interaction behavior of the Rock Bolt and the surrounding Rock mass, with a way of evaluating the supporting performance quantitatively.
Bo Wang - One of the best experts on this subject based on the ideXlab platform.
-
monitoring of pre load on Rock Bolt using piezoceramic transducer enabled time reversal method
Sensors, 2017Co-Authors: Bo Wang, Dongdong Chen, Gangbing SongAbstract:Rock Bolts ensure structural stability for tunnels and many other underground structures. The pre-load on a Rock Bolt plays an important role in the structural reinforcement and it is vital to monitor the pre-load status of Rock Bolts. In this paper, a Rock Bolt pre-load monitoring method based on the piezoceramic enabled time reversal method is proposed. A lead zirconate titanate (PZT) patch transducer, which works as an actuator to generate stress waves, is bonded onto the anchor plate of the Rock Bolt. A smart washer, which is fabricated by sandwiching a PZT patch between two metal rings, is installed between the hex nut and the anchor plate along the Rock Bolt. The smart washer functions as a sensor to detect the stress wave. With the increase of the pre-load values on the Rock Bolt, the effective contact surface area between the smart washer and the anchor plate, benefiting the stress wave propagation crossing the contact surface. With the help of time reversal technique, experimental results reveal that the magnitude of focused signal clearly increases with the increase of the pre-load on a Rock Bolt before the saturation which happens beyond a relatively high value of the pre-load. The proposed method provides an innovative and real time means to monitor the pre-load level of a Rock Bolt. By employing this method, the pre-load degradation process on a Rock Bolt can be clearly monitored. Please note that, currently, the proposed method applies to only new Rock Bolts, on which it is possible to install the PZT smart washer.
-
a load measuring anchor plate for Rock Bolt using fiber optic sensor
Smart Materials and Structures, 2017Co-Authors: Siu Chun Michael Ho, Bo Wang, Weijie Li, Gangbing SongAbstract:Rock Bolts are the devices that used to reinforce the Rock masses in mining tunnels and underground excavation structures. The loading level of the Rock Bolt indicates the reinforcing efficiency and is able to ensure safe underground operation by giving warnings to the underground miners prior to any accidents. Therefore, it is very important to monitor the load level of the Rock Bolts. In this short communication, we propose a smart anchor plate, a simple but effective device that uses fiber Bragg gratings (FBG) type optic sensor, to monitor the load level of the Rock Bolt. Instead of measuring the stress/strain on the Rock Bolt, which adds more complexity, the proposed method monitors the Rock Bolt load by measuring the load experience on the Rock Bolt anchor plate. Such a configuration has the advantages of simple structure and flexible implementation. In experimental observation, the FBG instrumented anchor plate is able to observe the load of the plate with good repeatability. This test will lead to further in-depth studies involving finite element analysis as well as more complex applications.
-
a review of Rock Bolt monitoring using smart sensors
Sensors, 2017Co-Authors: Gangbing Song, Weijie Li, Bo Wang, Siu Chun Michael HoAbstract:Rock Bolts have been widely used as Rock reinforcing members in underground coal mine roadways and tunnels. Failures of Rock Bolts occur as a result of overloading, corrosion, seismic burst and bad grouting, leading to catastrophic economic and personnel losses. Monitoring the health condition of the Rock Bolts plays an important role in ensuring the safe operation of underground mines. This work presents a brief introduction on the types of Rock Bolts followed by a comprehensive review of Rock Bolt monitoring using smart sensors. Smart sensors that are used to assess Rock Bolt integrity are reviewed to provide a firm perception of the application of smart sensors for enhanced performance and reliability of Rock Bolts. The most widely used smart sensors for Rock Bolt monitoring are the piezoelectric sensors and the fiber optic sensors. The methodologies and principles of these smart sensors are reviewed from the point of view of Rock Bolt integrity monitoring. The applications of smart sensors in monitoring the critical status of Rock Bolts, such as the axial force, corrosion occurrence, grout quality and resin delamination, are highlighted. In addition, several prototypes or commercially available smart Rock Bolt devices are also introduced.
-
measurement of the length of installed Rock Bolt based on stress wave reflection by using a giant magnetostrictive gms actuator and a pzt sensor
Sensors, 2017Co-Authors: Weijie Li, Bo Wang, Qingqing Fu, Gangbing SongAbstract: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.
Weijie Li - One of the best experts on this subject based on the ideXlab platform.
-
a load measuring anchor plate for Rock Bolt using fiber optic sensor
Smart Materials and Structures, 2017Co-Authors: Siu Chun Michael Ho, Bo Wang, Weijie Li, Gangbing SongAbstract:Rock Bolts are the devices that used to reinforce the Rock masses in mining tunnels and underground excavation structures. The loading level of the Rock Bolt indicates the reinforcing efficiency and is able to ensure safe underground operation by giving warnings to the underground miners prior to any accidents. Therefore, it is very important to monitor the load level of the Rock Bolts. In this short communication, we propose a smart anchor plate, a simple but effective device that uses fiber Bragg gratings (FBG) type optic sensor, to monitor the load level of the Rock Bolt. Instead of measuring the stress/strain on the Rock Bolt, which adds more complexity, the proposed method monitors the Rock Bolt load by measuring the load experience on the Rock Bolt anchor plate. Such a configuration has the advantages of simple structure and flexible implementation. In experimental observation, the FBG instrumented anchor plate is able to observe the load of the plate with good repeatability. This test will lead to further in-depth studies involving finite element analysis as well as more complex applications.
-
a review of Rock Bolt monitoring using smart sensors
Sensors, 2017Co-Authors: Gangbing Song, Weijie Li, Bo Wang, Siu Chun Michael HoAbstract:Rock Bolts have been widely used as Rock reinforcing members in underground coal mine roadways and tunnels. Failures of Rock Bolts occur as a result of overloading, corrosion, seismic burst and bad grouting, leading to catastrophic economic and personnel losses. Monitoring the health condition of the Rock Bolts plays an important role in ensuring the safe operation of underground mines. This work presents a brief introduction on the types of Rock Bolts followed by a comprehensive review of Rock Bolt monitoring using smart sensors. Smart sensors that are used to assess Rock Bolt integrity are reviewed to provide a firm perception of the application of smart sensors for enhanced performance and reliability of Rock Bolts. The most widely used smart sensors for Rock Bolt monitoring are the piezoelectric sensors and the fiber optic sensors. The methodologies and principles of these smart sensors are reviewed from the point of view of Rock Bolt integrity monitoring. The applications of smart sensors in monitoring the critical status of Rock Bolts, such as the axial force, corrosion occurrence, grout quality and resin delamination, are highlighted. In addition, several prototypes or commercially available smart Rock Bolt devices are also introduced.
-
measurement of the length of installed Rock Bolt based on stress wave reflection by using a giant magnetostrictive gms actuator and a pzt sensor
Sensors, 2017Co-Authors: Weijie Li, Bo Wang, Qingqing Fu, Gangbing SongAbstract: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.
