ABSTRACT
This chapter discusses the changes in ground stresses due to mining. Underground excavation causes rearrangement of stress since the load formerly supported by the rock removed must be borne by the remaining rock. Coal pillars are mostly in a state of triaxial compression since lateral constraint arises from sliding resistance on the roof and floor. A uniaxial state will theoretically occur only when the pillar is considerably higher than wide. A number of investigations have dealt with the extent of the abutment zone ahead of longwall faces and pillar lines. A number of rockbursts are known to have happened at the same time as or shortly after normal shotfiring, even at distances of 30 m or more from the blast area. The percentage of such bursts in some statistics is too high to be explained by mere coincidence, it rather proves that bursts can be initiated by vibrations.
