Ground falls mines

Roof bolts and the ATRS are the first lines of defense against roof falls in underground coal mines. When miners go under unsupported roof, they are completely unprotected. Between 1996 and 1998, approximately 25% of coal mine roof and rib fatalities occurred when miners were beyond roof supports. While there are no grounds for complacency, the recent record does represent an improvement from a decade ago, when nearly 50% of ground fall fatalities occurred beneath unsupported roof (Peters 1992). The improvement was achieved through new equipment, enforcement and a persistent educational campaign. 

Roof bolt operators are on the front line in the fight against ground falls. They are continually exposed to roof and rib hazards, and historically they have experienced more groimdfall-ielated injuries than any other occupation in mining. Although large roof and rib falls have been responsible for several fatalities, most injuries are caused by relatively small pieces of rock. 

This chapter has presented an overview of the most significant ground control hazards facing todays mineworkers. Underground miners, particularly in coal mines, are at the greatest risk from ground falls. The six highwall and slope fatalities that occurred in the first half of 1999 show that surface miners are at risk as well. 

Sources of lead in dust and soil include lead that falls to the ground from the air, and weathering and chipping of lead-based paint from buildings and other structures. Lead in dust may also come from windblown soil. Disposal of lead in municipal and hazardous waste dump sites may also add lead to soil. Mining wastes that have been used for sandlots, driveways, and roadbeds can also be sources of lead. 

Figures 7.64 and 7.65 provide a view of the fracture surface of a bolt recovered following a fall of ground from a hardrock mine. This is at magnification x 10. A close-up of dimpled areas is presented in Figure 7.66, at a magnification x 1500. The dimples are shallow and inclined characteristic of ductile fracture. No sign of cleavage or quasicleavage, is observed (absence of river pattern that would be associated with brittle fracture). In the upper right part of the photo dimpled areas are masked by oxidation.

Benner S. G., Blowes D. W., and Ptacek C. J. (1997) A full-scale porous reactive wall for prevention of acid mine drainage. In Ground Water Monitoring and Remediation, Fall, vol. 17(4), pp. 99-107. 

Cheap mixture of ammonium nitrate, water, aluminium powder and polystyrene adhesive as a bonding agent. First used in the 6.75 t free fall bomb BLU-82 ( Daisy cutter or aerosol bomb ). The peak pressure of the bomb ignited approximately 1 m above ground reaches 70 bar in a radius of 30 m. GSX has been used for mine field clearing and for Instant helicopter landing zones in the Viet Nam jungle-war. 

Ground control The regulation and final arresting of the closure of the walls of a mined area the term generally refers to measures taken to prevent roof falls or coal bursts. 

TABLE 23.1 Fatalities from 1996 to 1998 by commodity for both falls of ground and other mining classifications ... 

Surface mines have relatively few serious falls of ground, with six fatalities in the period from 1996 to... 

Altounyan, P.F.R., D.N. Bigby, K.G. Hurt, and H.V. Peake. 1997. Instrumentation and procedures for routine monitoring of reinforced mine roadways to prevent falls of ground. Paper presented at the 27th International Conference of Safety in Mines Research Institute. New Delhi, India. 759-766. 

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