Vibration instability of laser base and atmospheric refraction in the process of aligning and operational control of underground mine shafts: effects and methods of mitigation

Reliable operation of underground mine shafts is strongly conditioned by the proper position of the shaft frame and the installations inside the shaft tube in relation to the vertical direction. For operational reasons and safety, they are subject to periodical control and emergency control in the case when the permissible values of the operational parameters are likely to be exceeded. These can be, for instance, the values of tilt of the shaft frame or of the irregularity of the bars which guide the conveyance (i.e. cage or skip) in the shaft. One of the reasons of such a situation to occur can be the movement of the ground in the closer or farther proximity of the shaft, as a consequence of the effects of mining, hydro-geological changes in the ground, etc.