Working with GROT GPRs in Belarussia
October 10, 2009
The aim of the work was to specify the location of the control stem borehole at Starobin potassium salts deposit in the Republic of Belarus to ensure the safety of mining operations. If the control stem borehole is beyond the contours of a worked-out mine shafts in the area of flooded rocks, than the requirements of water protection aren’t met.
To estimate this risk it is necessary to determine with the sufficient accuracy the place, at which the contours of the mine shafts adjoin the control stem borehole, as well as the possible boreholes location areas at the mining works level. It should be taken into account that the insignificant rocks watercut at the lower part of the marl clay stratum cannot cause the mine flooding, but it can cause some complications in the mine operation, if the control stem boreholes are undercut at the place, where it boarders the shafts contours. After borehole drilling completion and its hydrogeological and geophysical study the borehole was cemented. In solving the problem of the 1K borehole location determining the geophysical methods selection was conducted, after which they included the GPR survey, high-frequency seismic methods and ultrasound studies. The diameter of the borehole and fractured rocks around it reached 20-25 cm.
To determine the location of the 2K borehole the GPR survey was conducted using the tracking method. At the stage of the research and methodical works with salt rocks, which included the third potash horizon, the value of the dielectric constant was determined to be approximately equal to 8.
Experimental works allowed determining the scanning depth of the GROT 12 ground penetrating radar. For example, using the 2-meter antennas the possible research depth with the stratification is more than 40 meters, using the same antennas the possible research depth with the cross stratification is just over 30 meters.
In the course of the research and methodical works the optimal system with the use of the tracking method of georadar scanning was determined. Basing on the mine workings size we have chosen the antennas length equal to 2 meters. The transmitting and receiving antennas had a combined structure (standard version 1 m + flexible version 1 m). This combination allowed minimizing the risk of interference, caused by the tracks roughness.