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Support technology
Published in Emilio Bilotta, Renato Casale, Claudio Giulio di Prisco, Salvatore Miliziano, Daniele Peila, Andrea Pigorini, Enrico Maria Pizzarotti, Handbook on Tunnels and Underground Works, 2023
L. Schiavinato, P. Ferrante, E. Bertino, A. Luciani, M. Pescara, S. Airoldi, M. Bringiotti
Combination rock bolts are end-point-anchored bolts that can be fully grouted afterward (e.g., CT-bolts or Mix-Bolts). Polyethylene (PVC) or PP sleeve give these bolts additional protection from corrosion. They are relatively stiff since they are both end-point-anchored and fully grouted. Thus, they are very convenient for use in weak rocks or heavily jointed rocks (Figure 3.22). CT-bolts are, however, not applicable in rock masses where high deformations can be expected since their stiffness can lead to failure in the rock bolts.
The evolution of support and reinforcement philosophy and practice for underground mining excavations
Published in Ernesto Villaescusa, Christopher R. Windsor, Alan G. Thompson, Rock Support and Reinforcement Practice in Mining, 2018
The rock engineering expertise developed on the Snowy, including rock bolting technology, was soon transferred to the Australian mining industry. Rock bolts are now the most widely used reinforcing element in underground mines and civil construction. Many types of bolt including friction stabilisers and end- and fully-resin grouted bolts have since been developed (see Hoek et al 1995 and Windsor & Thompson 1993 for descriptions). New bolt types and installation techniques continue to evolve (eg Chen & Collopy 1999, Villaescusa & Wright 1999). Quality control and corrosion of rock bolts have become important issues in recent years and are addressed by a number of the papers presented to this conference (eg Logan 1999, Li & Lindblad 1999, Robinson & Tyler 1999, Villaescusa 1999).
Behaviour of full grouted rock bolts subjected to repeated dynamic loading
Published in Charlie C. Li, Xing Li, Zong-Xian Zhang, Rock Dynamics – Experiments, Theories and Applications, 2018
Q. Wu, F. Zhao, Z.H. Zhou, Y. Li, S.P. Zhang
Anchorage technology is an important means for rock bolts or cables to be used to reinforce the rock-mass and applied widely to mining, tunneling and various rock engineering. The main purpose of the rock bolts is to increase the resistance to deformation and control the failure of surrounding rock. Rock bolts can also be combined with other supporting devices, such as concrete lining, metal net and steel band, to reinforce different geological conditions of rock mass in rock engineering. However, the working conditions become more complex with the increase of mining depth, and the failure of rock bolt is very common, such as loss of pre-stressing, failure of rock bolt at the end. The phenomenon has a major negative impact on the safety of the workers and the schedule of the project. Therefore, it is necessary to study the mechanical properties and failure mechanism of rock bolt.
Experimental and numerical analysis of in situ pull-out tests on rock bolts in claystones
Published in European Journal of Environmental and Civil Engineering, 2021
Richard Giot, Christophe Auvray, Simon Raude, Albert Giraud
There are many different types of rock bolts; however, they can be classified into two categories: active and passive rock bolts (Grasselli, 2005). Active rock bolts apply a positive load to the rock mass and are made of a steel bar that is anchored in the rock on one extremity with a plate and fixed by a nut on the other extremity. Active rock bolts are always tensioned after installation and may be sealed by a grout or a resin for long-term applications. The anchorage may either be punctual at the end of the borehole at which they are installed or distributed along the entire length of the bolt, either through a sealing product or rock/bolt friction. Passive rock bolts only react to the deformation of the rock mass; thus, they must be installed before significant movement of the rock mass has occurred. Passive rock bolts can be punctually anchored to the rock mass (through mechanical anchorage or localized grouting) or fully anchored to the rock mass along their entire length (either through friction or a sealing grout), in addition to other types of classifications. Based on the concept of load transfer between the reinforcement and rock mass, Windsor and Thompson (1993) proposed a classification of rock bolts as a function of the load transfer mechanism (Figure 1): continuous mechanical coupling (CMC), continuous friction coupling (CFC) and discontinuous mechanical or friction coupling (DMFC).
Experimental study on mechanical properties of fractured rock mass under different anchoring modes
Published in European Journal of Environmental and Civil Engineering, 2020
Guangfeng Lei, Quansheng Liu, Xingxin Peng, Lai Wei
The natural rock mass is mostly non-continuum due to the existence of weak structural planes such as joints and cracks, many theoretical researches and engineering practices show that the destabilisation of rock mass is mostly related to its internal crack extension and perforation(Pellet & Egger, 1996). Rock bolts can significantly improve the mechanical properties of fractured rock mass, limit the expansion and coalescence of internal cracks within rock mass, and enhance the integrity and stability of fractured rock mass. For the above reasons, bolt anchoring has been widely used in many geotechnical reinforcement engineering fields such as highway tunnels and embankment slopes. However, the distribution of joints, cracks and other structural planes in the rock mass is random and complex, so the theoretical research on anchoring mechanism is far behind engineering practice, the design of most anchoring reinforcement engineering are based on empirical and semi-empirical methods, which lead to a huge security risk and economic waste. For decades, a great deal of experimental and theoretical researches on bolt anchoring mechanism of fractured rock mass have been carried out by many experts and scholars, and many substantial progresses have been made (Bjurstrom, 1974; Carranza-Torres, 2009; Chen, Hagan, & Saydam, 2016; Chen & Li, 2015; Huang, Liu, Liu, et al., 2017; Li & Doucet, 2012).
Numerical simulation of the reinforcement effect of rock bolts in granular mixtures
Published in European Journal of Environmental and Civil Engineering, 2019
Chao Hu, Hua-kang Zheng, Wei Zhou, Gang Ma, Lei Hu
Granular materials are widely involved in geotechnical engineering, for example, crushed rock mass, natural gravel, rockfill in slopes, underground caverns, hydraulic structures, etc. Granular materials are complex discontinuous media. To increase the stability of granular materials, rock bolts can be used. Good design of rock bolts can effectively control the deformation. It has become an economic and effective method to improve the stability in geotechnical engineering. Furthermore, the use of rock bolts is one of the most common reinforcement methods. However, the current knowledge does not supply satisfactory information for reasonable and systematic design. Therefore, further studies of the rock bolt reinforcement mechanism in granular mixtures and its effects are needed.