# Structural Evaluation of Cable Bolts under Static Loading
## 2 Literature Review
### Ground Support System Elements
#### 2.2.1 Reinforcement Support Elements  
Since the development of rock reinforcement systems, yielding bolts were only widely accepted from the early 2000s. This was due to misbelief of the effectiveness of reinforcement bolts that were designed to purposely yield [16]. Despite [PERSON] (1992) [20] conducting a field test in 1969 that clearly demonstrated the effectiveness of yielding reinforcement, it was not until multiple mines that were prone to rock bursting displayed the success of yielding reinforcement, such as the Big Bell Mine in Australia [21] and Brunswick Mine in Canada [22], did yielding bolts become widely used in burst-prone excavations.  
Conventional rock bolts have been categorised into three major categories, which are mechanical bolts, fully grouted rebar bolts and frictional bolts [23]. These types of conventional bolts are utilised to deal with rock instability in areas with relatively low in situ stress. However, in burst-prone mines, energy-absorbing rock bolts (also knownas yielding bolts) are more suitable due to their shear resistance under dynamic loading conditions that rock burst creates.  
When there are more attune to burst-prone environments, energy-absorbing rock bolts are better suited due to their large deformation capacity [24].  
The Cone Bolt was the first energy-absorbing rock bolt designed, which consisted of a smooth bar with a flattened conical shape on the far end of the bolt [25]. The original cone bolt was designed to be grounded using cement, but the cone bolt was later adapted to function with resin by adding a threaded section and mixing blade [26]. The bolt was designed such that when displacement occurs, the conical end prolongs through the resin or grout to conduct work and absorb energy released from the rock. After [PERSON] (2000) carried out dynamic testing on modified cone bolts, it was recorded that the bolts were only effective when ploughing occurred. Further dynamic analysis by [PERSON], [PERSON] and [PERSON] (2010) [3] showed an average dynamic yield loading between 50 and 216 kN when a kinetic energy of 33 kJ was inputted, presenting a large spread of values due to different failure mechanisms, including ploughing, steel stretching or a combination of the two.  
Currently, common dynamic rock bolts used in the Australian mining industry include the Yield Lok Bolt and the J-Tech All Thread Bar, which are produced by Jennmar Australia. The Yield Lok Bolt typically consists of a smooth steel bar with a portion of threaded bar (for resin mixing) with an upset, a type of anchor that is coated in an engineered polymer. Like the cone bolt, the Yield Lok bolt absorbs energy via bolt shank slippage through ploughing in grout/resin. The J-Tech bolt consists of a bolt that has a small pitch thread along the entirety of its length with exceptional static and dynamic capacity.  
In addition to rock bolts, cable bolts research and usage in burst-prone grounds are increasing. Cable bolts perform like rock bolts, but cable bolts consist of flexible tendons with higher tensile strength to further strengthen rock mass [27]. Plain strand cables had poor load transfers properties when first introduced in ground support systems, which is reflective of their initial use as a secondary reinforcing member. However, after modifications such as indentation, double strands, birdcage strands, bulbed strands, fiberglass cable bolts and nut-caged cable bolts, the load transferring and energy absorption capacity has improved [2]. Currently, SUMO (9 wire strand) and Secta (7 wire strand) dynamic cable bolts with bulbed strands are popular in the Australian Mining industry.