Introduction Winter weather can slow or completely stop surface mining operations. Winter weather can increase injury rates, illness figures and maintenance cost. Let’s look at some of the ground control hazards caused by winter weather.
Types of Ground Control Hazards Ground control hazards associated with highwalls include: –Freezing and thawing –Loose material –Cracks –Erosion –Auger holes
Freezing and Thawing Water in a highwall can freeze and turn into ice which expands and exerts force on surrounding surfaces. This pressure separates the material. Ice will bind the material together until the temperature rises, the ice then will melt and the highwall will become unstable.
Loose Material Loose material is a potential hazard at all times around highwalls, even when freezing and thawing is not present. All loose material should be scaled when miners work in these areas. Even small pieces of rock can cause serious injury when falling from great heights. Therefore, inspections should be made frequently to identify hazards.
Cracks Miners should always be alert for cracks when working around highwalls whether man made or natural. Cracks can be vertical or horizontal. Horizontal cracks can be especially dangerous since they are not easily detected. If the crack is behind the face of the highwall it can only be seen from on top.
Erosion Air and water weaken the stability of the material that make up the highwall. Heavy rain can most often contribute to highwall erosion. Heavy rain can cause previously good highwalls to become hazardous, and it can make poor walls much worse. Many accidents near highwalls have followed bad weather, especially rain storms.
Auger Holes Auger mining is normally used when it becomes too expensive to remove the overburden. Auger mining can cause cracks which weaken the highwall. The highwall cracks due to material that has been removed which previously supported the weight of the overburden.
Spoil Bank Hazards The term spoil bank designates an accumulation of overburden as the overburden is removed. The spoil may be located around the side of a hill. Weathering and erosion can cause spoil banks to fall. Miners need to be alert for slips in spoil banks. Slips are similar to landslides as materials separate and slide away.
Spoil Bank Hazards Cont… Slips are likely to happen where: –Material is loosely gathered. –Weathering erodes the spoil bank. –Material is not sloped properly. –Small amounts of material are coming down first. Remember that slips can be just as hazardous as a crack in the highwall.
Instructor’s Guide Discuss specific areas at your mine where freezing and thawing create ground hazards. Discuss the importance of doing proper work area inspections-paying particular attention to horizontal cracks. Enlist the help of all employees to report hazards during rainy weather. Review the quiz.
Quiz 1.Winter weather can increase injury rates and maintenance cost. T or F 2.Highwalls are the unexcavated face of exposed overburden. T or F 3.Water can freeze and turn into ice which expands and exerts pressure on highwalls. T or F
Quiz Cont… 4.It is not important to do frequent inspections of highwalls. T or F 5.A horizontal crack may not be seen by a miner behind the face of the highwall. T or F 6.Air and water weaken the stability of the material that make up the highwall. T or F
Quiz Cont… 7.Heavy rain has no effect on highwall erosion. T or F 8.Auger mining is usually done when it becomes very costly to remove any more of the overburden. T or F 9.A spoil bank is stockpiled overburden. T or F 10.A Slip can be just as hazardous as a a crack in the highwall. T or F