I am investigating civil engineering contract work and am interested to find out if any members have any examples of yield curves for the ripping of in situ rock by mechanical means. For instance a bulldozer of a particular flywheel power may rip in situ rock at a particular rate (say 80 cubic metres per hour). What rate would a bulldozer of 30% more flywheel power be expected to achieve? In concrete crushing or tensile testing of steel the stress applied reduces after the yield stress has been reached giving a graph curve which starts as a relatively steep curve but flattens after the yield point is reached. Are there any examples of similar curves for rock?