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.

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 The Analytical Approach to Evaluate the Load-Displacement Relationship of Rock Bolts

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Jianhang Chen ◽  
Shengli Yang ◽  
Hongbao Zhao ◽  
Junwen Zhang ◽  
Fulian He ◽  
...  
Keyword(s):  
Shear Strength ◽  
Young’S Modulus ◽  
Analytical Model ◽  
Load Transfer ◽  
Young's Modulus ◽  
Peak Load ◽  
Rock Bolts ◽  
Residual Shear Strength ◽  
Grouted Rock Bolts ◽  
Elastic Softening

Fully grouted rock bolts are widely used in civil engineering and mining engineering, playing a significant role in keeping the stability and safety of excavations. In this paper, the load transfer mechanism of fully grouted rock bolts was studied with an analytical model. A trilinear model was used to depict the bond-slip behaviour of the bolt/grout interface. The displacement of the confining medium was involved in this analytical model. Then, the shear stress propagation along the bolt/grout interface was analysed in the elastic, elastic-softening, elastic-softening-debonding, softening-debonding, and debonding stages. Experimental pull-out tests were used to validate this analytical model. There was a good correlation between experimental and analytical results. A parametric study was conducted to evaluate the influence of Young’s modulus of the confining medium, the shear strength of the bolt/grout interface, and the residual shear strength of the bolt/grout interface on the load transfer performance of rock bolts. The results show that increasing Young’s modulus of the confining medium was beneficial for improving the load transfer performance of rock bolts. However, once Young’s modulus of the confining medium was beyond a critical limit, it had marginal effect on the peak load of rock bolts. Furthermore, increasing the shear strength of the bolt/grout interface and the residual shear strength of the bolt/grout interface led to rising of the peak load of rock bolts. However, compared with the residual shear strength of the bolt/grout interface, increasing the shear strength of the bolt/grout interface had more apparent effect in improving the peak load of rock bolts.

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 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
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