Inflatable rock bolt bond strength versus rock mass rating (RMR): A comparative analysis of pull-out testing data from underground mines in Nevada

2016 ◽  
Vol 26 (1) ◽  
pp. 19-22 ◽  
Author(s):  
Chase Barnard ◽  
Raj R. Kallu ◽  
Sean Warren ◽  
Rahul Thareja
Keyword(s):  
Rock Mass ◽  
Comparative Analysis ◽  
Bond Strength ◽  
Rock Bolt ◽  
Underground Mines ◽  
Rock Mass Rating ◽  
Pull Out ◽  
Testing Data

scholarly journals Weightage Effect during Back-Calculation of Rock-Mass Quality from the Installed Tunnel Support in Rock-Mass Rating and Tunneling Quality Index System

2019 ◽  
Vol 9 (10) ◽  
pp. 2065 ◽  
Author(s):  
Jonguk Kim ◽  
Hafeezur Rehman ◽  
Wahid Ali ◽  
Abdul Muntaqim Naji ◽  
Hankyu Yoo
Keyword(s):  
Rock Mass ◽  
Quality Index ◽  
Rock Bolt ◽  
Rock Mass Rating ◽  
Rock Mass Quality ◽  
Back Calculation ◽  
The Difference ◽  
Bolt Spacing ◽  
Q System ◽  
Selection Of

In extensively used empirical rock-mass classification systems, the rock-mass rating (RMR) and tunneling quality index (Q) system, rock-mass quality, and tunnel span are used for the selection of rock bolt length and spacing and shotcrete thickness. In both systems, the rock bolt spacing and shotcrete thickness selection are based on the same principle, which is used for the back-calculation of the rock-mass quality. For back-calculation, there is no criterion for the selection of rock-bolt-spacing-based rock-mass quality weightage and shotcrete thickness along with tunnel-span-based rock-mass quality weightage. To determine this weightage effect during the back-calculation, five weightage cases are selected, explained through example, and applied using published data. In the RMR system, the weightage effect is expressed in terms of the difference between the calculated and back-calculated rock-mass quality in the two versions of RMR. In the Q system, the weightage effect is presented in plots of stress reduction factor versus relative block size. The results show that the weightage effect during back-calculation not only depends on the difference in rock-bolt-spacing-based rock-mass quality and shotcrete along with tunnel-span-based rock-mass quality, but also on their corresponding values.

Experimental Research on Interfacial Bond Performance in Rock Anchor with High-Performance Grouting Medium

2012 ◽  
Vol 517 ◽  
pp. 932-938 ◽  
Author(s):  
Zhi Fang ◽  
Hong Qiao Zhang
Keyword(s):  
Rock Mass ◽  
Bond Strength ◽  
High Performance ◽  
Interfacial Bond ◽  
Interfacial Bond Strength ◽  
Bond Performance ◽  
Pull Out ◽  
Steel Bar ◽  
Reactive Powder ◽  
Ground Anchor

There exist the problems such as low bond strength and bad durability in the ordinary grouting slurry of the ground anchor system at present. The high-performance grouting mediums RPC (Reactive Powder Concrete) and DSP (Densified Systems containing homogeneously arranged ultrafine Particles) would become the potential replacement of grouting medium in ground anchor resulting from their high compressive strength, durability and toughness. Based on a series of pull-out tests on ground anchors with different high-performance grouting medium of RPC and DSP , different bond length in the construction field, the bond performance on the interfaces between anchor bolt (deformed steel bar) and grouted medium as well as between grouted medium and rock mass was studied. The results indicate that the interfacial bond strength between RPC or DSP and deformed steel bolt ranges within 23-31Mpa, far greater than that (about 2-3MPa) between the ordinary cementitious grout and deformed steel bar. Even though the interfacial bond strength between the grouted medium and rock mass of limestone was not obtained in the test since the failure mode was pull-out of those steel bar rather than the interface shear failure between grouted medium and rock mass, the bond stress on the interface reached 6.2-8.38 MPa, also far greater than the bond strength (about 0.1-3MPa) between the ordinary cementitious slurry and rocks.

Experimental Bond Behavior of Mortar Grouted GFRP Rock Bolt

2011 ◽  
Vol 261-263 ◽  
pp. 1244-1248 ◽  
Author(s):  
Qi Neng Weng ◽  
Yong Yuan ◽  
Qian Guan Zhang
Keyword(s):  
Rock Mass ◽  
Concrete Block ◽  
Rock Bolt ◽  
Rock Bolts ◽  
Engineering Structures ◽  
Bond Behavior ◽  
Gfrp Bars ◽  
Pull Out ◽  
Glass Fiber Reinforced ◽  
Concrete Blocks

Bolts are widely used in slope engineering, tunnel and large cave supporting structures, as well as restoration of engineering structures. They can improve the strength and stability of ground, rock mass, and other structures. The traditional steel bolt has some disadvantages, such as easy corrosion, heavy weight, and difficult operation. Glass Fiber Reinforced Polymer (GFRP) is more resistant to chloride, stronger and lighter than steel. Those advantages make it a better alternative in some fields of engineering. To utilize GFRP bars as rock bolt, some aspects of its behavior, such as bond strength in mortar, bearing capacity, and bond stress distributing along its interface, have to be examined. This paper presents a research on bond behavior of GFRP rock bolts. A concrete block is used to represent rock mass in laboratory. Modified pull out tests were conducted on selected GFRP bars and compared with steel ones that were grouted with mortar in concrete blocks. Bond characteristics of mortar grouted GFRP rock bolts with diameter 16mm were mainly evaluated and other specs of bolts were also discussed.

Rôle du scellement dans les ancrages actifs scellés dans le rocher

1986 ◽  
Vol 23 (4) ◽  
pp. 481-489 ◽  
Author(s):  
Gérard Ballivy ◽  
Brahim Benmokrane ◽  
Pierre Claude Aitcin
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Rock Mass ◽  
Bond Strength ◽  
Key Words ◽  
Creep Test ◽  
Cement Grout ◽  
Pull Out ◽  
Cement Grouts ◽  
Pull Out Strength

The dimensioning of anchor bars grouted in rock takes into account the mechanical properties of the three components steel, grout, and rock. The allowable bond strength at the rock–grout interface recommended by different national codes is generally selected according to the type of rocks and assuming an ordinary cement grout. In the present approach, the influence of the type of grout on the pull-out strength of anchor bars in a sound rock mass with mechanical properties equal or higher than the grout is considered. This experimental study shows that certain cement grouts can develop pull-out strength clearly higher than those obtained with epoxy grouts for example. Key words: rock mass, grouted anchors, cement grouts, epoxy grouts, pull-out test, creep test. [Journal translation]

scholarly journals Classification of Factors Affecting the Performance of Fully Grouted Rock Bolts with Empirical Classification Systems

2019 ◽  
Vol 9 (22) ◽  
pp. 4781 ◽  
Author(s):  
Haneol Kim ◽  
Hafeezur Rehman ◽  
Wahid Ali ◽  
Abdul Muntaqim Naji ◽  
Jung-joo Kim ◽  
...  
Keyword(s):  
Rock Mass ◽  
Field Experiments ◽  
Classification Systems ◽  
Rock Bolt ◽  
Rock Bolts ◽  
Tunnel Support ◽  
Support Materials ◽  
Pull Out ◽  
Controllable Factors ◽  
Grouted Rock Bolts

Empirical classification systems do not provide details of the factors that affect the performance of fully grouted rock bolts, as they are based on average values. Fully grouted rock-bolt patterns during tunnel-support design are a part of the composite support, and they are functions of rock-mass quality and tunnel span. Various fully grouted rock bolts are used in situ in different environments, along with other tunnel-support materials in static and dynamic environments during tunnel construction. The rock-bolt performances are evaluated through pull-out tests that follow ASTM standards. Several field pull-out tests were conducted on cement and resin grouted rock bolts. Under groundwater flow conditions, inflated steel tube rock bolts were tested and the results were compared with fully grouted rock bolts. Based on field experiments and previous studies, the factors that affect rock bolt performances are divided into five groups with respective sub-factors. Natural parameters cannot be controlled to ensure safety, economy, and stability in tunnels. The controllable factors, too, can be varied only within a practical range. In conclusion, the factors investigated here should be considered with the empirical support pattern of rock-mass classification systems for safe and economical design.

Fiber-matrix bond strength by pull-out tests on slag-based geopolymer with embedded glass and carbon fibers

2021 ◽  
pp. 1-11
Author(s):  
Lais Alves ◽  
Nordine Leklou ◽  
Pascal Casari ◽  
Silvio de Barros
Keyword(s):  
Bond Strength ◽  
Carbon Fibers ◽  
Pull Out ◽  
Fiber Matrix

scholarly journals Finite-difference based response surface methodology to optimize tailgate support systems in longwall coal mining

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Satar Mahdevari ◽  
Mohammad Hayati
Keyword(s):  
Compressive Strength ◽  
Response Surface Methodology ◽  
Rock Mass ◽  
Finite Difference ◽  
Longwall Mining ◽  
Support Systems ◽  
Rock Mass Rating ◽  
Slake Durability Index ◽  
Proposed Model ◽  
Durability Index

AbstractDesigning a suitable support system is of great importance in longwall mining to ensure the safe and stable working conditions over the entire life of the mine. In high-speed mechanized longwall mining, the most vulnerable zones to failure are roof strata in the vicinity of the tailgate roadway and T-junctions. Severe roof displacements are occurred in the tailgate roadway due to the high-stress concentrations around the exposed roof span. In this respect, Response Surface Methodology (RSM) was utilized to optimize tailgate support systems in the Tabas longwall coal mine, northeast of Iran. The nine geomechanical parameters were obtained through the field and laboratory studies including density, uniaxial compressive strength, angle of internal friction, cohesion, shear strength, tensile strength, Young’s modulus, slake durability index, and rock mass rating. A design of experiment was developed through considering a Central Composite Design (CCD) on the independent variables. The 149 experiments are resulted based on the output of CCD, and were introduced to a software package of finite difference numerical method to calculate the maximum roof displacements (dmax) in each experiment as the response of design. Therefore, the geomechanical variables are merged and consolidated into a modified quadratic equation for prediction of the dmax. The proposed model was executed in four approaches of linear, two-factor interaction, quadratic, and cubic. The best squared correlation coefficient was obtained as 0.96. The prediction capability of the model was examined by testing on some unseen real data that were monitored at the mine. The proposed model appears to give a high goodness of fit with the accuracy of 0.90. These results indicate the accuracy and reliability of the developed model, which may be considered as a reliable tool for optimizing or redesigning the support systems in longwall tailgates. Analysis of variance (ANOVA) was performed to identify the key variables affecting the dmax, and to recognize their pairwise interaction effects. The key parameters influencing the dmax are respectively found to be slake durability index, Young’s modulus, uniaxial compressive strength, and rock mass rating.

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