In the exploitation of water-soluble ore deposits, of particular importance is the preservation of the impermeability of the waterproofing layers. This is achieved by using a heading-and-stall method with a rigid pillar which excludes sharp deformation of impermeable layers.
To control the deformation processes, a network of ground reference points is installed on the earth's surface. The main problem with this approach is the limited number of reference point lines, caused by the high cost of installing the equipment and the occupation of the surface area.
In these conditions, underground measurements are very important.
To identify the main pattern of deformation processes in pillars and choose the most informative indicators, mine studies including deformation measurements using contour and deep reference points were carried out. These measurements were carried out in various mining and geological conditions.
The measurement results showed that the most informative parameter for pillar stability estimation is its transversal strain.
A new system based on a magnetostrictive sensor, recorder and transmitter to realize continuous remote monitoring of pillars deformation is suggested in the article. The system makes it possible to measure axial displacement in a 76 mm borehole with an accuracy of 0.01 mm and transmit the results on a land surface using a standard mine telecommunication line or save it in the internal memory in case of autonomic working.
This system can be used for displacement control in mining and underground construction.
When developing salt and potash deposits, the main objective of ensuring safe conditions for mining operations is to preserve the continuity of the water-blocking strata that separate overlying watered layers of terrigenous and carbonate rocks from productive strata during the mine's whole service life. This is achieved by using the heading- and-stall method with a rigid pillar; the method excludes sharp deformation of waterproof layers. However, the practice of mining operations shows that, even when all the requirements of regulatory documents in the course of the design of mining operations and mining of reserves are met, there are still adverse phenomena that are manifested in the destruction of pillar selvedges and, in some cases, these result in breaking the continuity of the waterproof strata. The world knows more than 80 cases of salt mines flooding as a result of the ingress of oversalt fresh waters into a mined-out area. In most cases, a major reason for accidents in the mines of the Upper Kama potash salt deposit is the non-compliance of the room and pillar method parameters (width of rooms and rib pillars) with the mining and geological conditions of the specific areas to be mined.
