回帖：There are six types of common failure mechanisms of shallow stopes of hard rock mines:
• rock fracturing:
Rupture of the surface crown pillar and collapse into the shallow stope.
• plug failure:
Sudden fall of the surface crown pillar, delineated by its boundary planes, by gravity into the shallow stope. The planes are well-defined, with near to vertically dipping uninterrupted discontinuities with low shear strength. The pillar thickness can vary; plugs up to 660 m high have occurred .
Failure potential depends considerably on the confinement available from redistributed stresses around the stope to resist movement; areas of numerous regional shallow stopes are prime candidates for plug failures.
Rarely do visual precursor movements occur, although smaller scale movements do open discontinuities and allow for water flow. Failure occurs suddenly and completely as a block.
• ravelling:
Peripheral block by block rock mass failure without a self-support cavity form reached which includes delamination), ravelling failure involving sliding or buckling of thin rock layers at stope boundaries leading to the deStabilization of the surface crown pillar.
Gradual failure from an unsupported periphery of unfavorably oriented rock blocks, or those where discontinuity orientations are relatively shallow, is commonplace when the span exceeds self-support capabilities, but very low peripheral compressive stresses are required to keep blocks in place .
Blocks fail without the remainder of the rock mass mobilizing on a large scale unless a stable self-supported arch cavity is formed.
• strata failure:
Tensile failure of stratified rock at wall contacts or along the surface crown pillar span.
Few case studies of vertically progressing delaminations have reached surface. The poor cross-jointing normally shown by the rock masses make the strata stiffer and limits failure heights to shallow domes. In other cases, massive block failures have occurred when pillars fail in room and pillar mining. Such failures quickly choke off because of high bulking factors.
• chimneying disintegration:
The upward progression of disintegration within a weak rock mass forming a cavity with limited lateral extent (