scholarly journals Laboratory pull-out tests on fully grouted rock bolts and cable bolts: Results and lessons learned

2017 ◽  
Vol 9 (5) ◽  
pp. 843-855 ◽  
Author(s):  
Isabelle Thenevin ◽  
Laura Blanco-Martín ◽  
Faouzi Hadj-Hassen ◽  
Jacques Schleifer ◽  
Zbigniew Lubosik ◽  
...  
Keyword(s):  
Lessons Learned ◽  
Rock Bolts ◽  
Pull Out ◽  
Cable Bolts ◽  
Grouted Rock Bolts

scholarly journals Investigation of Load Bearing Capacities of Grouted Rock Bolts with New Auxetic Head Designs

2020 ◽  
Author(s):  
Eren Komurlu ◽  
Aysegul Durmus Demir ◽  
Atila Gurhan Celik
Keyword(s):  
Numerical Modelling ◽  
Energy Absorption ◽  
Experimental Studies ◽  
Head Part ◽  
Rock Bolts ◽  
Load Bearing ◽  
Ratio Effect ◽  
Pull Out ◽  
Drill Holes ◽  
Grouted Rock Bolts

Within this study, new bolt heads were designed to be able to expand in drill holes as the load applied on the bolt shank increases. The heads of newly designed rock bolts include a conic part and split rings encircling them. To determine load bearing capacities of new rock bolts with varying angles of the conic parts and expansion properties, a series of deformation controlled pull-out tests were carried out by using bolt samples grouted in rock blocks. In addition to the experimental studies, numerical modelling analyses were performed to better understand the support properties of newly designed rock bolts. Because of a negative Poisson’s ratio effect supplied by the head part expansion with the tension of the shank, new bolt heads are suggested to be defined as auxetic. According to the results of this study, the new head designs significantly improve the load bearing and energy absorption capacities of grouted rock bolts.

scholarly journals Study on Mechanical Characteristics of Fully Grouted Rock Bolts for Underground Caverns under Seismic Loads

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Guoqing Liu ◽  
Ming Xiao ◽  
Juntao Chen ◽  
Hao Zhou
Keyword(s):  
Mechanical Characteristics ◽  
Load Transfer ◽  
Seismic Load ◽  
Seismic Loads ◽  
Stress Distributions ◽  
Rock Bolts ◽  
Pull Out ◽  
Underground Caverns ◽  
Grouted Rock Bolts

This study establishes an analytical model for the interaction between the bolt and surrounding rock based on the bearing mechanism of fully grouted rock bolts. The corresponding controlled differential equation for load transfer is deduced. The stress distributions of the anchorage body are obtained by solving the equations. A dynamic algorithm for the bolt considering shear damage on the anchoring interface is proposed based on the dynamic finite element method. The rationality of the algorithm is verified by a pull-out test and excavation simulation of a rounded tunnel. Then, a case study on the mechanical characteristics of the bolts in underground caverns under seismic loads is conducted. The results indicate that the seismic load may lead to stress originating from the bolts and damage on the anchoring interface. The key positions of the antiseismic support can be determined using the numerical simulation. The calculated results can serve as a reference for the antiseismic optimal design of bolts in underground caverns.

Stability Analysis of Central Haulage in Baluba Copper Mine

2014 ◽  
Vol 638-640 ◽  
pp. 822-828
Author(s):  
Gao Hui Yao ◽  
Yi Ming Wang ◽  
Kai Jian Hu
Keyword(s):  
Rock Mass ◽  
Stability Analysis ◽  
Mathematical Modelling ◽  
Rock Bolts ◽  
The Poor ◽  
Support Measures ◽  
Cable Bolts ◽  
Induced Stresses ◽  
Protection Pillar ◽  
Grouted Rock Bolts

Site observations were conducted to investigate the reasons for the poor current rock-mass conditions being experienced in essential crosscuts, to provide recommendations for remedial support measures. Conceptual analyses of mining induced stresses within abutment pillars were undertaken using elastic analytical and mathematical modelling. The results showed that damage to the crosscuts is due to high mining-induced stresses, with the major stress probably acting vertically, the protection pillar for the 480 Level crosscut should be at least 100 m wide. The research demonstrated that only 2.4 m grouted rock-bolts and timber sets is not enough in these conditions, so the 480 Level and 580 Level central haulage should be re-supported with a combination of 4.0 m pre-tensioned cable-bolts, a 75 mm layer of steel mesh (or fibre) reinforced shotcrete, and even steel arch sets with lots of log.

scholarly journals Bond Failure of Rock Bolts and Cable Bolts in a Pull-out Test.

2002 ◽  
pp. 97-106 ◽  
Author(s):  
Yuzo OBARA ◽  
Yasukazu MAENO ◽  
Ryuichi KAWANO ◽  
Fumio ITO ◽  
Fumiharu NAKAHARA
Keyword(s):  
Bond Failure ◽  
Rock Bolts ◽  
Pull Out ◽  
Cable Bolts

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.

The Performance of Axially Loaded, Fully Grouted Rock Bolts Based on Pull-Out Experiments Utilizing Fiber Optics Technology and Associated Numerical Modelling of Such Support Elements

2019 ◽  
Vol 38 (2) ◽  
pp. 1389-1407 ◽  
Author(s):  
Nicholas Vlachopoulos ◽  
Daniel Cruz ◽  
Bryan Stanley Anthony Tatone ◽  
Andrea Lisjak ◽  
Omid K. Mahabadi ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Fiber Optics ◽  
Rock Bolts ◽  
Pull Out ◽  
Axially Loaded ◽  
Grouted Rock Bolts

scholarly journals Pull-out and Critical Embedment Length of Grouted Rebar Rock Bolts-Mechanisms When Approaching and Reaching the Ultimate Load

2021 ◽  
Author(s):  
Are Håvard Høien ◽  
Charlie C. Li ◽  
Ning Zhang
Keyword(s):  
Ultimate Load ◽  
Failure Mechanisms ◽  
Concrete Block ◽  
Rock Bolts ◽  
Rock Stratum ◽  
Pull Out ◽  
Deformation Length ◽  
Embedment Length ◽  
Pull Tests ◽  
Grouted Bolts

AbstractRock bolts are one of the main measures used to reinforce unstable blocks in a rock mass. The embedment length of fully grouted bolts in the stable and competent rock stratum behind the unstable rock blocks is an important parameter in determining overall bolt length. It is required that the bolt section in the stable stratum must be longer than the critical embedment length to ensure the bolt will not slip when loaded. Several series of pull tests were carried out on fully grouted rebar bolts to evaluate the pull-out mechanics of the bolts. Bolt specimens with different embedment lengths and water/cement ratios were installed in either a concrete block of one cubic meter or in steel cylinders. Load displacement was recorded during testing. For some of the bolts loaded beyond the yield load, permanent plastic steel deformation was also recorded. Based on the test results, three types of failure mechanisms were identified, corresponding to three loading conditions: (1) pull-out below the yield strength of the bolt steel; (2) pull-out between the yield and ultimate loads, that is, during strain hardening of the steel; and (3) steel failure at the ultimate load. For failure mechanisms 2 and 3, it was found that the critical embedment length of the bolt included three components: an elastic deformation length, a plastic deformation length and a completely debonded length due to the formation of a failure cone at the borehole collar.

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