<font color=blue> At some point the rock is just too big for machinery. I wonder at what weight that is.</font color=blue>
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), : <font color=blue>… 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)</font color=blue>
So, I guess the rule is, try to move it first, and if that fails, blow it up! /w3tcompact/icons/smile.gif
Roy