A new optical sensing technique for monitoring shear of rock bolts

Forbes, Bradley; Vlachopoulos, Nicholas; Hyett, A. J.; Diederichs, Mark S.

doi:10.1016/j.tust.2017.03.007

Cited by 34 publications

(12 citation statements)

References 20 publications

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“…The groove dimension provides ample space for the optical fiber to be situated below the exterior profile of the rebar but, more importantly, it provides a protective barrier once encapsulated. However, care must be taken to run the optical fiber straight within the groove to avoid potential orientation difficulties if more than one groove is to be analyzed (Forbes et al 2017). A comparison between several different bonding agents was discussed by Forbes (2015).…”

Section: Rock Bolt Supportmentioning

confidence: 99%

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The application of distributed optical strain sensing to measure the strain distribution of ground support members

Forbes

Vlachopoulos

Hyett³

2018

FACETS

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A distributed optical strain-sensing technique is presented as a solution for measuring the strain distribution along ground support members used in tunnelling and mining works. The technique employs a Rayleigh optical frequency domain reflectometry technology, which measures strain at a spatial resolution of 0.65 mm along the length of a standard optical fiber. A rationale for selecting this technology as a potential monitoring technique for ground support elements over alternative commercially available technologies is discussed. The development of a technique to couple optical fiber sensors with rock bolt, umbrella arch, and cable bolt support members is also demonstrated. A robust laboratory investigation of such optically instrumented support members demonstrated the capability of the technique to capture the expected in situ support behaviour in the form of coaxial, lateral, and shear loading arrangements as would be anticipated in the field. Moreover, the microscale data obtained by this optical sensing technique are shown to provide unprecedented insight into the local/micro-scale geomechanistic complexities associated with the bearing capacity of ground support members, especially when compared with data obtained by discrete strain-sensing technologies.Key words: distributed optical strain sensing, ground support, rock bolt, cable bolt, strain measurement, strain profile OPEN ACCESSCitation: Forbes B, Vlachopoulos N, and Hyett AJ. 2018. The application of distributed optical strain sensing to measure the strain distribution of ground support members. FACETS 3: 195-226.

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Section: Rock Bolt Supportmentioning

confidence: 99%

“…7). This provides both a redundancy measure and a method to compensate for bending-induced strain Forbes et al 2017). Validation of this FOS technique was accomplished by conducting an end-loaded, elastic tensile test with an 800 mm testing span using a 500 kN servo-controlled loading frame.…”

Section: Rock Bolt Supportmentioning

confidence: 99%

The application of distributed optical strain sensing to measure the strain distribution of ground support members

Forbes

Vlachopoulos

Hyett³

2018

FACETS

Self Cite

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“…Numerous of rock engineering applications such as civil and mining engineering projects have proved that the instability and integral failure of the rock mass have great correlations with extensions and propagations of weak discontinuities [15]. The reinforcement for jointed rock mass using rock bolts has always been one of the most effective and economical geo-structural reinforcing technologies widely used in rock engineering projects for more than 100 years since 1913 in Germany [16][17][18][19][20][21]. However, instability of anchored rock mass caused by bolt failure often occurs [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

“…The reinforcement for jointed rock mass using rock bolts has always been one of the most effective and economical geo-structural reinforcing technologies widely used in rock engineering projects for more than 100 years since 1913 in Germany [16][17][18][19][20][21]. However, instability of anchored rock mass caused by bolt failure often occurs [21][22][23]. Rock bolt failure in the field could be attributed to the tension (joint opening) or the shear along the joint [17,22,24,25].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Shear Behavior and Failure Mechanism of Bolted Heterogeneous Rock Joints under Different Anchorage Conditions

et al. 2021

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Despite their frequent natural occurrence and engineering encounter, heterogeneous rock joints (rock joints with different lithological characters on both sides of the joint surface) have been studied much less systematically. To study the shear behavior and failure mechanism of bolted heterogeneous rock joints, laboratory tests were performed on the heterogeneous rock joints having different joint roughness coefficients (JRC) under different anchorage conditions. The results indicate that shear strength increases with the increase of JRC, showing exponential growth. Under the same roughness, the shear strengths of rock joints from large to small are fully grouted, end anchorage, and without anchorage. The mechanical characteristics of the bolt and joint are poorly matched under the end anchorage condition, which is easy to cause these two to be broken one by one. Under fully grouted, the extrusion force caused by the rock bolt will diffuse around the anchorage agent and will not cause partial continuous damage. The surface damage of heterogeneous rock joints increases with the increase of JRC and presents obvious heterogeneous characteristics. The shear dislocation between the blocks under shear load results in the interaction between the bolt and surrounding media. Under the action of shear force, the bolt body produced both axial and transverse deformation, which leads to breakage of anchorage agent and rock mass. Rock bolt has a significant impact on the shear behavior of the anchorage system, and the damage of the rock bolt to rock mass should be considered in rock engineering reinforcement design.

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“…Liu et al [15] applied the dynamic distributed measurement capability of the PPP-BOTDA to monitor the structural damage under in-service operations. The BOTDA and fiber Bragg grating (FBG) sensing technology have been used to measure the stress distribution along the bolt [16]. However, in practical applications, the applicable measurement range and repeatability of the two methods need to be further studied.…”

Section: Introductionmentioning

confidence: 99%

Assessing the Difference in Measuring Bolt Stress: A Comparison of Two Optical Fiber Sensing Techniques

Chai

Liu

et al. 2018

Journal of Sensors

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Monitoring the load level of the rock bolts is of great importance for assessing risk. Based on the mechanical transmission mechanism of grouting bolts, the bolt pull-out test was carried out in lab. The performance of the bolt under pull-out loading was measured using the pulse-pre-pump Brillouin optical time domain analysis (PPP-BOTDA) and fiber Bragg grating (FBG) sensing technologies. The distribution characteristic of axial stress along the bolt was analysed in combination with the measurements obtained by the two sensing technologies. The relative standard deviation for repeatability errors in the determination and the setting time of resin grout was investigated. The results show that the distribution of axial stress is nonuniform along the anchorage section. The maximum value of axial stress on the bolt is closed to the pull-out side. The relative standard deviation for repeatability errors obtained by PPP-BOTDA is less than that obtained by FBG. The comparison of the measurements obtained by the two methods indicates that when the drawing force is greater than 20 kN and the axial stress is more than 10 kN, the two methods have better consistency. In the field application, it is necessary to estimate the deformation of matrix, leaving at least 500 minutes for resin bond to work.

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A new optical sensing technique for monitoring shear of rock bolts

Cited by 34 publications

References 20 publications

The application of distributed optical strain sensing to measure the strain distribution of ground support members

The application of distributed optical strain sensing to measure the strain distribution of ground support members

Experimental Study on Shear Behavior and Failure Mechanism of Bolted Heterogeneous Rock Joints under Different Anchorage Conditions

Assessing the Difference in Measuring Bolt Stress: A Comparison of Two Optical Fiber Sensing Techniques

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