Goaf stability is a long-standing problem. But almost all conclusions about goaf-integral-stability-evaluation are on a qualitative level

especially for the goaf in condition of large-scale and complex underground mines. If be quantified

it will

to a better extent

provide some protections for mine safety. For the problem of goaf stability in large-scale

the concept of “failure probability of goaf” based on numerical simulation is introduced to try to answer it. In the postprocessing of FLAC3D

several aspects of failure probability of goaf in the principal stress and shear failure criterion Fs and elastic energy are researched and analyzed respectively

in which the basic principles of probability of statistics are subjected to 95% confidence interval

and "Excel" plugin @Risk is used to statistically analyze the calculation results of grid in FLAC3D; then it makes the stability problem of goaf been quantified. Finally

a conclusion that the principal stresses and elastic energy of rock grid cells in large number follow Weibull distribution and Lognormal distribution has been drawn as well. At the same time

quantification not only solves the problem of the goaf stability

but also makes application of numerical simulation broadened.