Actual evidence of the model of compression and shear fracture nucleus of rock for earthquakes.

The model and shape equation of compression and shear fracture nucleus of rock of earthquakes are briefly recounted in this paper. Recently rock breaking areas with two special shapes have been discovered on palisade of foundation pit excavated for dam in Hunan Province, PR China. The on-the-spot investigation indicates that all two broken areas once had the stress concentration point, and the broken area was initiated and expanded from this point. Both internal crack propagation and the outline shape are consistent separately with the rock compression and shear fracture nucleus with leaf shape of KI, KII mode and the rock compression and torsion fracture nucleus with bud shape of KI, KIII mode given by the shape equations. The further research on the forming process of rock compression and shear fracture nucleus is helpful for impending earthquake prediction. [ABSTRACT FROM AUTHOR]