Dev. 1: Fractured Rock in Development Face After Blasting
Blasting as well as mining induced stresses causes the hanging wall to fracture. Mostly fracturing is also taking place during the shift. This together with dilatational movement of the rock result in the deterioration of the hanging wall throughout the shift. Therefore even if the making safe measures were taken in the beginning of the shift the hanging- and sidewall conditions could become unsafe during the shift.
Dev. 2: Presence of Geological Features and Brows
The presence of geological features combined with mining induced stress fractures and bedding planes often results in the formation of unstable blocks of ground and brows, which are hazardous unless identified and sufficiently supported or otherwise made safe. The situation is aggravated when the haulages intersects faults and dykes at a shallow angle.
Dev. 3: Friable Hanging wall and Sidewall Due to Poor Marking, Drilling, Charging Up and Timing of Blast Holes
Poor drilling and charging up of blast holes result in unnecessary blast damage to the rock surfaces and create cross fracturing and friable hanging wall conditions thus increasing the likelihood of falls of ground. Furthermore poor drilling and charging up practices result in an unnecessary large excavation.
Dev. 4: Poor Quality Grouting of Rock Tendons
Quality of capsule grouting has been identified as an industry wide problem already for a quite some time. Poorly grouted rock tendons will result that the required bond strength i.e. the required support resistance not being achieved. This in turn would increase the likelihood of falls of ground.
Similarly if the rock studs with mechanical end anchors are not tensioned properly the desired, active support resistance is not achieved and the likelihood of falls of ground is increased.
Dev. 5: Hangingwall Conditions at Breakaways and when Widening of Existing Tunnels
The sudden increase in open span due to the blasting of breakaways and widening of existing tunnels might induce sudden bed separation resulting in falls of ground. The situation is made more hazardous if the breakaway is developed or widening is carried out in close vicinity to or intersecting faults and dykes.
Dev.6: Development Through or in Close Proximity to Mined Out Areas
Development of tunnels and travelling ways through or in close vicinity to mined out areas is a potential rock fall hazard. A fracture zone surrounds stopes, which due to gravity can be a source of falls of ground.