Large Rocks?

GrantMO · Mar 28, 2001

Boondox,
That's a good story, somehow I figured that explosives were going to come into play in the end. About 25 years ago the spring rains loosened a small house size boulder that slid down on a very heavily travelled road near here. They had to blast it too. At some point the rock is just too big for machinery. I wonder at what weight that is.

Roy · Mar 29, 2001

At some point the rock is just too big for machinery. I wonder at what weight that is.

At first, I thought that we could estimate. By getting some accounts of how large (what physical size) these unmovable rocks were, we could compute volume (assume a sphere). Using the average mass of various rock types, estimate the total weight, and therefore size (type dependent). But, alas, my own search for mass information was fruitless. The only information I could find was like that at the University of Michigan “Tunnelling: Mechanics and hazards” (http://www.umich.edu/~gs265/tunnel.htm), : … the descriptions of rock masses can be extremely complex, and are much more so than for soils. The reason for this is that, although rocks have a greater innate strength than a soil, their mechanical characteristics are dominated by the effect of anisotropy (the state of a characteristic of the rock being different in different directions) and the discontinuities contained within. These discontinuities may range from foliation in the rock , such
as the layering in a schist or the fissibility of a shale. The discontinuities may also take the form of fractures, ranging from the minuscule cracks to major faulting.
(Parker, 1996)

So, I guess the rule is, try to move it first, and if that fails, blow it up! /w3tcompact/icons/smile.gif

Roy

Jag · Mar 29, 2001

Roy, from my engineering books, solid rock will vary, soft rock will run from just above 100 lbs/cf, sandstone 140-150 lbs/cf, granite 170-180 lbs/cf up a little over 200 lbs/cfs for certain very dense rocks... Most times just figure 150 times the volumn and you will be close.... For reference dry soil is normal 95 to 105 lbs, damp 105 to 125 lbs or so, concrete is normally 150 lbs/cf.

Edited by JAG on 03/29/01 06:16 PM (server time).

Roy · Mar 29, 2001

Jag; So, if we get some size observations from these guys, then we can make a weight guess-amate! I tried to find weight values, but only found (like the cited example) on why they would not give density! Good going!

OK… If someone can report the estimated physical dimensions of these unmovable objects, we should be able to estimate a weight range for those beasts.

Roy

GrantMO · Mar 29, 2001

Roy,
I'm guessing the rock was about 50X30X15 and and least partly limestone.

Roy · Mar 30, 2001

That's a house! So 50'x30'15' = 22,500 cuf * 150 lbs/cuf = 3,375,000 lbs!!!!

Can this actually be?

Roy

gerard · Mar 30, 2001

Whish I could find the picture in "Farm Show" magazine but a few issues ago they had a picture of a HUGE rock that they were pulling by using 2 huge D8 dozers and 5 big farm tractors, all daisy chained together. That had to be SOME chain!!

As an aside I pull small rocks that are too big to fit in my bucket using a chain with slip hook. I wouldn't use strap because I look at that as a big rubber band with a hook on the end and I don't want to be on the other end IF it breaks! Chain doesn't have as much elasticity if it breaks.

Roy · Mar 30, 2001

Remind me to never complain about my rocks! The largest ones I have dealt with were probably around .5 cubic feet (figuring 1'x 1'x 6"). They fit in the loader nicely, and only weigh 50 to 75 lbs (guessing 100 to 150 lbs per cubic foot).

Roy

Rick572 · Mar 30, 2001

Several years ago I had an opportunity to deal will several large rocks used in a landscape project. What we did was lift one end of the rock and then placed a couple pieces of steel pipe under the rock, then did the same with the other end. Once the rock is suspended on the pipes, about four of them, it offers only a fraction of the resistance as before. We lifted the end of the rock with a high-lift jack and a chain. Its kinda a two man operation. We pulled our rocks with a jeep very slowly and as the rock kicked out a piece of pipe we replaced it in front of the rock. One drawback, is that the ground must be fairly flat and if its as wet as it is here in TX it would require placing some boards down for the pipe to role on. Its slow, but with enough time and patience I believe almost any size rock can be moved and not damaged.

Rick