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Gold/Mining/Energy : Winspear Resources -- Ignore unavailable to you. Want to Upgrade?

To: Gord Bolton who wrote (17016)	3/27/1999 5:01:00 PM
From: jack hampton	Read Replies (3) \| Respond to of 26850

Hi Gord. How to mine this thing...... Haven't seen any core so I don't know how competent the ore is or the hangingwall (roof) or footwall (floor) but if it is fairly strong then this is how to mine it....and I'll try not to use too much mining lingo. From the surface, tunnel down at about a -15% gradient until you are a good 50 metres below surface. The ore above 50 metres is the crown pillar to keep out groundwater mostly. Tunnel into the ore zone and then room and pillar the ore out. So from the main tunnel a multitude of additional tunnels are created somewhat perpendicular to the original. If the dip is 11-13 degrees which is my understanding, this does not create too many problems. If over 20 degrees, this is a problem. Tunnelling is done using 2 boom drill jumbos. This is a diesel powered rubber tired mobile drill about 8 metres long that generally drills 50mm diameter 4 metre deep holes into the tunnel face. The holes are drilled in such a way that when loaded with explosives (Ammonium nitrate and 6% fuel oil) and blasted a nice tunnel profile is left along with about 250 tonnes of broken ore. It takes about 2 hours to "drill off a round" which may consist of 40 or 50 holes. Blasting takes 1-2 more and then getting rid of the rock with low profile front end loaders (LHD's or scooptrams) takes another 2 or 3 hours. The tunnel then likely needs ground support to ensure it does not cave in the future. Such support would take about 6 hours to install. So for 250 tonnes of ore from one tunnel you probably tie up 3-4 men for the better part of a day. A contractor would charge you about $10,000 to get that 250 tonnes out of the mine and the tunnel ready for the next round. If you did it with company men, maybe about $5,000 to $6,000 not including equipment costs. Since the ore zone is narrow, and you need a flat floor to drive all that equipment around on, you need to mine a wedge of waste rock below the ore zone. The roof of the tunnel however would be inclined to follow the top of the ore zone. Minimum mining heights are in the 3-3.5 metre range for the equipment required. Therefore, mining (milling)ore grade would be only about 80% of the geological grade If the haul to surface is greater than about 500 metres than the front end loaders will likely load trucks underground that have a payload of 26-40 tonnes each which then haul it up the decline to surface. If you have lots of tonnage (+10 Mtonnes?) , installing a conveyor with an underground crusher central to the orebody is justified cost wise. On surface, the big problem is the ore freezes to make an unworkable mass so the plant design needs to take this into account by probably using a jaw crusher as the first step of the mill process. So for a 1500 tpd room and pillar mine underground you would need: 2 or 3 drill jumbos 3 or 4 front end loaders 3 or 4 haulage trucks 2 or 3 bolting jumbos or scissor lift trucks for ground support 3 or 4 personnel/service vehicles All up this gear would cost new about $C8M. However,using contractors can save a lot of upfront costs (but prove more expensive in the end). A crew of about 30 miners should do on site at one time for 1500 tpd. Ground support can be the big wild card. Some mines need very little if the ground is good, some other mines, the ground support drives them out of business. Mining costs are just one small part of the total costs. Just flying people in and out could set you back $C1M per annum easy.