China
Africa
Explore chapters and articles related to this topic
Ground stabilization
Published in M.L. Jeremic, Ground Mechanics in Hard Rock Mining, 2020
Until now, ground reinforcement and consolidation by freezing has had very limited application in underground hard rock mining, except in some isolated cases. This type of ground consolidation is broadly used in the soft rock mining, particularly for shaft sinking and drifting through water-bearing horizons and quick-sand strata. However, the idea of ground reinforcement by freezing came of interest in new technology developments in hard rock mining as, for example, the stabilization of mine fill as discussed in the case of bulk mining methods (Chapter 12).
An overview of rock support design
Published in E. Hoek, P.K. Kaiser, W. Rbawden, Support of Underground Excavations in Hard Rock, 2000
E. Hoek, P.K. Kaiser, W. Rbawden
The size and shape of potential wedges in the rock mass surrounding an opening depends upon the size, shape and orientation of the opening and also upon the orientation of the significant discontinuity sets. The three-dimensional geometry of the problem necessitates a set of relatively tedious calculations. While these can be performed by hand, it is far more efficient to utilise one of the computer programs which are available. One such program, called UNWEDGE 1, was developed specifically for use in underground hard rock mining and is utilised in the following discussion.
The performance of mechanical anchors in South African mechanized deep level gold mining
Published in Charlie C. Li, Xing Li, Zong-Xian Zhang, Rock Dynamics – Experiments, Theories and Applications, 2018
The history of underground hard rock mining in South Africa dates back to the late 1800’s (Langille 1995, Sengani & Kataka 2017). Underground mining usually creates excavations of varying sizes in the surrounding rock mass. The rock mass is never homogenous, can be of varying rock strength, can be traversed by geological disturbances as well as subjected to changing stress fields (Sengani & Kataka 2017). During mining, the excavations need support. Failure to support can result in the collapse of the excavations on varying scales, causing injuries to miners as well as disruptions to mining, which in turn can affect the mine’s productivity. The safety and life of such excavations can be maximized if properly designed mining layouts are in place accompanied by the use of correct support systems. Some excavations like tunnels are planned for long time usage and therefore require effective support. As mining progress towards ultra-deep mining levels, the stress levels increases rapidly, compromising the stability of the tunnels and excavations intersections (Zvarivadza et al. 2017, Sengani & Zvarivadza 2017). Tunnels driven into highly stressed ground typically suffer from stress-induced damage (Wagner 1984, Ortlepp 1992, Villaescusa & Wright 1997, Sengani & Kataka 2017). Stress-induced damage can form from either creation of new fractures or reactivation of existing fractures in the rock mass. As a result of these challenges, rock support systems of underground excavations have changed significantly over the past decades due to improved technologies, experience gained and rock support requirements for different rock masses. The mechanical anchor system is an active reinforcement system, used to stabilize large single blocks or wedges formed on the hangingwalls and sidewalls of underground excavations (Villaescusa et al. 1992). This reinforcement system tends to provide effective reinforcement of the excavation walls where normal rock bolts are inadequate due to their short embedment lengths (Thompson 2004). They can be used in a wide range of hole diameters from 25 mm to over 60 mm. Various steel diameters can be used to suite the required strengths (Thompson 2004). Mechanical bolts do have certain limitations in that if the correct torque is not applied on installation, inadequate load will be achieved. Load is also lost through ground vibration caused by blasting or other rock movement. If scaling occurs around the collar of the support hole, load is also lost. As a result, full column grout mechanical anchors have been introduced to eliminate some of the limitations associated with mechanical anchors (see Figure 1).
Performance analysis of electric and diesel equipment for battery replacement of tethered LHD vehicles in underground mining
Published in Mining Technology, 2020
Antonio Nieto, Richard S. Schatz, Cihan Dogruoz
The two most commonly used underground hard rock mining methods are caving methods such as block caving, and support methods both artificial and natural, such as cut-and-fill and room and pillar techniques, respectively. These techniques may also be used in soft rock mining; however, in hard rock mining, the high strength of the rock requires fewer underground supports than soft rock mining (Nieto 2011, p. 386).