ABSTRACT
The feature most common to seams in which rockbursts occur is the close proximity to strong, thick and rather rigid strata. In most coalfields these strata consist of sandstone, in rarer cases they consist of other types of what has been defined as competent massive elastic rock. From investigations at rockburst sites the following conditions have been found in coal mining districts. The state of stress which exists in rock undisturbed by human work is termed ‘natural’, ‘virgin’, or ‘primitive’. Its vertical component can be expected to be the pressure due to the weight of the overburden and therefore to increase in proportion to the depth below surface. Most rockbursts occur while some kind of work at the coalface is in progress. Pillar configurations account for a great deal of the rockbursts in coal mines, mainly when associated with extraction.
