EXPERIMENTAL STUDY OF THE NATURE AND CONSEQUENCES OF INTERACTION OF SALT ROCKS WITH HYDROFILLING BRINES DURING UNDERGROUND DEVELOPMENT OF POTASSIUM SALT DEPOSITS
Authors:   Institute of Problems of Integrated Subsoil Development named after Academician N.V. Melnikov, Russian Academy of Sciences, RADCHENKO Dmitry Nikolaevich , BERGER Roman Vladimirovich ,   Limited Liability Company «EuroChem-VolgaKaliy», TATARNIKOV Valentin Igorevich ,   Institute of Problems of Integrated Subsoil Development named after Academician N.V. Melnikov, Russian Academy of Sciences, ZUBKOV Pavel Olegovich ,   Institute of Problems of Integrated Subsoil Development named after Academician N.V. Melnikov, Russian Academy of Sciences
Published: October 2024

Introduction. The research methodology included selection and comparative tests of strength characteristics of the initial core of sylvinite and carnallite in air-dry condition and, respectively, core samples after their contact with model hydrofilling brines. During the tests on the press under uniaxial compression load it was noted that most of the samples are very heterogeneous, characterized by layering and the presence of various inclusions, varying even within the same well. The specimens differ in the character of deformation at compression failure. It seems that the character of contact of targets with hydrofilling brines is different than in the soil of mine workings, through which drainage brines will flow, where the processes of frizzling have been revealed, indicating the influence on the development of fracturing of sylvinite protective pack in the soil and on the side walls of targets. The obvious risk of drainage brines penetrating into the cracks and the nature of their movement through the soil of the workings require full coverage of the sylvinite samples with brine from all sides. Research results. It is established that as a result of contact of samples of sylvinite rocks with saturated brine there is a decrease in strength characteristics by 1.2-1.7 times. It is determined that as a result of contact with model brines the deformation diagram of samples under load has changed. Monolithic sample of carnallite after incubation for 58 days in concentrated salt brine there was a complete loss of strength and the sample crumbled in a measuring cup. On the basis of the performed researches it is concluded that at hydrofilling of the excavated space with saturated hydrofilling brines there will be a decrease in strength of the contour part of the massif of chambers, pillars and in the soil of drainage excavations. Conclusion. In the laboratory experiment the fact of decrease in uniaxial compression strength of salt rock samples was established: already on the 36th day of ageing in brine the strength of samples decreased by 24-25%, deformation modulus - by 22-28%. On 56 days the compressive strength of the specimen decreased on average by 2 times in comparison with the initial ones in air-dry condition. It is also proved that at carrying out of hydrofilling works with application of saturated brines there is a decrease in strength of rocks of the contour part of the massif of chambers and drainage excavations. For the chamber being laid these processes are not so critical, but the influence of hydrofill brines on the strength and deformation modulus reduction for the underlying rocks at the base of drainage excavations, through which the excess brine will flow. Reduced strength and deformation characteristics may result in an increased risk of accidents at the underground mine. Resume. The influence of brines of the potash mineral processing plant on selected sylvinite cores has been assessed. Regularities of change of strength characteristics of sylvinite samples on uniaxial compression in «dry» state and after prolonged soaking in saturated brine of the processing plant were established.