N G Nair Malanjkhand India.

Raising methods in under ground metal Mines

 Raising is a regular operation in the development of metalliferous mines. It is associated with danger of accidents – due to fall of roof rock, inadequate ventilation resulting in poor visibility at the work site and uncomfortable working conditions. Frequent climbing up and down the ladder, often with tools, between the working spot and lower level is quite tedious for the workers. The methods practiced for raising are: 

1. Open raising by drilling, blasting, mucking.
2. Two or three compartment raising.
3. Raising with Jora raise lift.
4. Raising by long hole drilling.
5. Raising with Alimak Raise Climber.
6. Raise bores – latest achievement
7. Drop raising method.

DROP RAISING - Mining

KHETRI COPPER MINES

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KHETRI COPPER COMPLEX AND Malanjkhand Copper Project.

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In India at the Copper Mines of Khetri Copper Complex. This is a method of making a raise connection between two adjacent levels, nearly 60 m apart, by drilling large dia. holes(150 – 165 mm) through, from upper level to lower level and balsting them in stages. The raise is usually vertical but many also be steeply inclined. The charging and blasting of the holes is based on the recently devised method of Vertical Crater Retreat. The term cratering in blasting used in Crater Method are normally spherical or a geometric equivalent, as research in the application of this breakage mechanism to rock indicates that spherical charges or their equivalent produces optimum results. In blasting practice, , spherical charges have been defined as having a length : diameter (L : D) ratio of 4 : 1 or less, and upto but not exceeding a L : D equal to 6 : 1 or less, and upto but not exceeding a L : D equal to 6 : 1. Thus for holes 165 mm dia. an explosive charge of 165 mm dia. and 990 mm in length would constitute a pherical charge. At the Kolihan Copper Mines in K C C the raise is 3 m x 3m. The blast holes are 165mm dia, 5 in number (1 in centre, 4 at corners) drilled from the top level to the bottom level, nearly 57 m below. The charging of explosives into blast holes is done from the upper level. A Wooden plug in two pices tied to a nylon rope is lowered into the blast hole to plug the bottom mouth of the blast hole. Aggregate, nearly 12 mm in size, is stemmed for a length of 1 m followed by charging of Slurry explosives  for a length of 1.2. A detonating fuse is tied to the slurry explosives cartideges below they are lowered into the hole. Above it a length of 1.8 m is packed with sand and the rest of the hole is left unstemmed. All the five blast holes are charged and they are blasted in a sequence with the help of delay detonators at a time from the surface when no worker is allowed to remain  underground. The roof of the lower level provides a free face for the explosive charged and the result of blasting is that a cavity of nearly 1.8 m height is formed. The fragmentation is sufficiently good for loading by LHD units. Dressing of the conical cavity is not ester. As the mucking is in progress the upper portions of the blast holes are charged with explosives in the manner as already described and the operation of loading, blasting and mucking follow smilar pattern,. With each blasting a vertical height of 1.8 m is found in the shape of a raise. The top 404.5 m of the blast holes, called plug, is however blasted in one step. The raise so formed has its sides sufficiently strong and stable showing no adverse effect by the heavy blasting.View more about Metal Minining in India.

GOPANKURAMR NAIR – TECHNORATI.COM.

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Sarla Nair Balaghat Dist. Malanjkhand India

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Rahul Nair Software Engineer. Infosys.

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My Home at Khetrinagar, Rajasthan. India

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Sarla Nair Copper Mines in India.

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sarla Nair Open Cast Copper Mines, India.

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Sarla Nair Ottapalam Kerala State, India.

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