The company that I am working with is operating a start-up Iron ore mine - we've been operating for 2 months, and are trying to come up with a good estimate on how much material we have stockpiled up till now. We are having a little internal debate about the meaning of stuck vs. heaped. Does struck mean that there is, let's say, a 2:1 pile in the back and the top of that pile is flush with the top of the truck, or does struck mean the entire volume of the back is 100% full? Might anyone have some pictures of struck vs. heaped loads? Thanks for your time, and for helping with our learning curve.
The struck capacity is simply a theoretical capacity based on an envelope covered by the dump body. Imagine putting a load of sand in the body and then scraping it level with the top rail cappings of the sideboards right along the length of the body, then tapering down the tail end to the floor. That's the struck capacity and it only really exists in theory as a mathematical calculation. The 2:1 SAE heaped capacity is basically the struck capacity plus a heaped load at a 2:1 angle on top up to a point in the centre. As a rule of thumb heaped capacity is generally about 1/3 more than struck. Depending on the material density and the size of the material if you load "heaped" the volume of material in the body will remain the same. However the weight you are hauling can change drastically with the size of the material hauled due to voids between rocks and also if you change the material density. Here is a photo showing what the heaped SAE 2:1 capacity looks like. Usually you can only achieve this hauling crushed coal as in this photo. If you are operating standard 740's (non-ejector model) without tailgates on the bodies your struck capacity is 18m3 and heaped 24m3. If you're hauling iron ore in standard size bodies then I would urge caution so that you don't overload. For a large mining truck a typical purpose-designed iron ore body would be about 2/3 the cubic volume of a rock body for the same truck model. According to some figures I have typical iron ore mine overburden will go between 1.7 & 2.2 tonnes/loose cubic metre (i.e. after blasting), let's for the sake of argument take the middle ground of 1.95 T/m3. Your 740's are rated as 39.5 metric tonnes maximum payload. 39.5/1.95 gives 20.25 cubic metres of loose material. So don't go piling the material on them or you'll be looking at broken chassis in the near future. That example is with overburden, I'm sure your iron ore will go much heavier. Typical fill factors for a dump body loaded with shot rock will range from about 85-90% of the SAE 2:1 heaped capacity, so in your case between 20.4 & 21.6m3. So from the above calculation you are in the ball park with overburden. I'd opine that if you get to loading iron ore all bets are off .........
Whatever you do don't be tempted to load like this ........... check out the front tyres
The specific gravity of the actual solid ore is 5.2. Broken it is "supposedly" 3.3. Here's a pic.
The tire walls have gotten like that in the back a few times, with loads that were maybe slightly larger than the picture above. Not in the front though. Thanks for the response.
The generally accepted "Swell Factor" after blasting between in-situ rock (bank density) and shot rock (loose density) is 33% given reasonable blasting. In other words 1 cubic metre of sold material "swells" to become 1.33 cubic metres when you blast it because of the voids created in it by the blasting process. So if your bank density is confirmed as 5.2 then the loose density by that factor should be 3.9, not 3.3. If the loose density is really 3.3 then that means you have an absolutely astounding Swell Factor of almost 60% if your Bank Density is confirmed as 5.2 ........***..? If the size of the material in the back of that truck is typical I would be more than happy happy to go with 33% Swell Factor from Bank to Loose. Can't your geologists confirm the numbers, or are they as useless as your place as they are here..? Here's a good ball park way of telling if you are overloaded. See the rear axle stabilizing link in your photo, the one that connects the "horn" on the LH side of the chassis to the RH side of the axle..? When the truck is empty and rises up on the suspension that link will be obviously higher at the LH side than at the RH side of the truck. When the truck is loaded on level ground that link should be pretty much horizontal, assuming the rear suspension is in good condition. If the truck is overloaded the LH end of the link will be noticably lower than the RH side.
I can't get a geologist to confirm anything. So yes, pretty much useless. Thanks for the response. More detailed: The spec gravity of the pure ore - unadulterated and concentrated - is 5.2. The stuff coming out of the hill has contaminants, etc. So I guess that was my mistake for putting that 5.2 number up without qualifying my statement. I found some info in this forum that says the swell factor of our material is 17-18% (link below). The ore at our mine is a mix of magnetite and hematite. Also, it is being excavated (bucket and hydraulic hammer) not blasted if that makes a difference. As I'm inexperienced at estimating these things how many cubic meters (or yards if you prefer) do you think are in the 740 in the picture there? http://www.google.com/url?sa=t&rct=...n_28BQ&usg=AFQjCNEtcKcdhMI4DZXCDeHxt7s5zpmQew
ACR I have hauled millions of yards of material of all types in 35 and 40 ton Cat and Volvo artic. trucks. On all the jobs I have a record of how many loads, and on most of them I get a survey for my pay volume. This gets me a very exact amount of material contained in the loads. It varies depending on the material, as each different material has a different swell factor. I base my hauling on bank cubic yards, as that is how I get paid. It matters to me none how many loose yards are in the truck, only what it was in the ground. I have never hauled iron ore before, but understand the weight involved. Looking at the load you have it appears to me that the swell is a little higher than Nige says. I would say it is at least 40%, in my opinion. A fully heaped load of that (don't do it) would likely be about 17 to 18 bank cubic yards. The load I see in the truck I would estimate to be no more than 11 to 13 bank cubic yards. The truck in you post has a 31 cy capacity at a 2:1 heaped load. Loading to the full rated capacity by volume in average material I will average between 18 to 20 CY per load. I am posting a few pictures of jobs showing my typical loads to get the volume I have referred to:
Looking at the material in your photo it does appear fairly blocky, so maybe my estimate of 33% for blasted material as a catch-all number is a bit on the low side. Excavating using a hammer will do that for you, so most probably Jerry's estimate of 40% minimum will be nearer the mark. He obviously got in before I did but my estimate would have been no more than 10 LCM (13 LCY) in that load, the equivalent of 7.14 BCM @ 40% swell factor which at 5.2 density gives you a payload of 37.15 tonnes on a truck that's rated at 39.5 tonnes. Pretty damn close, you could go a tad more on volume hauled per trip but not much. If your swell factor is more than 40% then obviously the BCM equivalent of what you have loose in the truck body will go down, and so will the tonnage. If you look back at my photo of the overloaded 797 you'll see that there is a large amount of material on the headboard, and so the resulting offset of the C of G of the load too far towards the front of the truck is what's causing the front tyres to swell. This would be even more pronounced if instead of being on level ground he was hauling downhill, which IIRC you are. So front-end overloading is a distinct possibility unless your loading machine operators are instructed to keep the load well spread out in the body instead of doing the typical thing and heaping a large part of it up against the front wall of the body. Let's face the material's so heavy you have plenty of spare body volume to play with. I would say that you have to look at worst case scenario for your ore. Go with the 5.2 density even though you may have some small level of contamination in it. I have no idea if you have any wheel loaders kicking around your operation, or in the local area. But if you want some accurate weights of what your loose ore weighs then getting hold of a wheel loader with a payload weighing system on it for a few days, maybe a week, and weighing a hundred truck loads to get some sort of "feel" for payloads could pay you enormous dividends, far in excess of the rental cost of the loader. Let's face it if renting a loader for a week saves you one failed chassis on an articulated truck it's more than paid for itself.
Now that is what I would call a full load. Anyone care to offer a guess at the weight ? 50T is my guess.
Unfortunately the photo was taken from the wrong angle to read the scoreboard (Digital Payload Display) - the rectangular black box just in front of the air tank with "19" written on it. That model of truck is rated for a payload of somewhere around 350 metric tonnes fully loaded . I'd wager the truck in that photo has well over 400 tonnes (440 of your US tons) on board, but if someone told me it was even more than that I'd believe them. This one you can read - 426 US tons/380 tonnes .........
But they did a good job on the bell curve Nige!!!! Yes the attitude and the front tyres are a give away. 2nd gear reweigh must not be being observed there, looks like a lovely little island site i know.
Gav, you may be right. Looking at the machine number I always had it pegged for a copper mine in Latin America that I visited on a regular basis for years, their trucks were numbered in that range. Maybe the cloudy sky gives it away, if it was in the Andes the sky would most likely be bright blue.