Purpose. To carry out comparative analysis of results concerning determination of stressstrain state (SSS) of shal low mine workings using calculation models for problems in elastic approach. Methodology. Rock mechanics methods; methods of analysis of the results of theoretical calculations and nu merical experiments using FEM. findings. Algorithm to calculate SSS of rock mass, involving extended mine working, has been substantiated. Nu merical experiment has demonstrated that to determine displacements within a mine working boundary it is required to consider plane strain state. It has been identified that the use of a plane stress state results in misinterpreted values of mine working boundary displacements to compare with accurate ones. The following basic conclusion has been made: it is possible to use adequate threedimensional (i.e. spatial) problem while arranging relations according to certain rules to solve the considered problem with a calculation model of limited length as for the research subject. originality. Divergence has been determined between extended mine working boundary displacements calculated using calculation models of a plane stress state (approximate analytical model), and those of a plane strain (accurate calculation model). It has been demonstrated that calculation of extended mine workings should involve analytical model of a plane deformation reflecting SSS of rock mass-mine working system adequately; otherwise, calculation er rors may be more than 100 % for horizontal displacements, and 25 % for vertical ones. Practical value. The obtained results make it possible to select reasonably calculation models for extended mine workings where support stiffness properties vary periodically. For instance, such mine workings are meant whose stability and deformability are provided by frame, anchor, combined frameanchor, complete reinforcedconcrete, reinforced equally distanced sequences of anchors, and similar support structures.

The strength criteria substantiation of water-saturated soils and mine rocks, which make it possible to obtain the analytical solutions necessary for determining the stability of water-flooded soil slopes and side-hills. Methods. The methods are applied of analysis and generalization of the theoretical and numerical experimental studies results. The rocks and soils characteristics are taken into account: specific cohesion c, internal friction angle φ, compressive strength R c and tensile strength R p of the rock, as well as the bulk density. The load q was imposed to the water-saturated seam roof from the overlying mine rock or soil seams, the weight of equipment or structures located on the surface. It was accepted that the seam is saturated with water (gas) with the excess pressure Р. A point on the mine working surface (or vertical slope surface), located at a depth z is considered. It is determined at which ratio of q, P and z parameters the soil or rock seam will be destroyed. The problem solution is based on the Mohr-Coulomb strength criterion. Findings. The strengths of water-saturated rock and water-free rock are compared. The ratios have been obtained that make possible to determine the critical load on the daylight surface of water-saturated and water-free vertical slopes, side-hills, trenches and foundation pits, as well as various mine workings in soil bases and mine rocks. The analytical solution has been obtained, which makes it possible to determine a value of the critical pressure on the water-flooded vertical surfaces and soil slopes. The generalization has been made of a certain one-dimensional Mohr-Coulomb strength condition for a water-saturated base characterized by the strength characteristics с and φ for the dimensional case. Originality. It has been theoretically proved that for any pore pressure value in the water-saturated mine rock (or soil) their strength will be less than in their water-free state. New solutions have been formulated for determining the critical height of a water-saturated vertical soil slope or the wall in the vertical mine working. Practical implications. The obtained results make it possible to solve the practical engineering problems on determining the stability of water-saturated slopes and side-hills with a load-free daylight surface, therewith, taking into account the weight of the equipment, stored material and the stability of vertical walls of water-saturated seams of open-cut mine workings.

UDC 662.215 O. L. Kyrychenko 1 , cand. Sc. (Tech.), orcid.org/0000-0002-1331-9323, V. V. Kulivar 2 , orcid.org/0000-0002-7817-9878, O. V. Skobenko 2 , cand. Sc. (Tech.), Assoc. Prof., orcid.org/0000-0003-4606-4889, O. V. Khalymendyk 2 , cand. Sc. (Tech.), Assoc. Prof., orcid.org/A TecHNique TO MeASuRe SeNSiTiViTy OF eXPLOSiVeS TO THe eFFecT OF LASeR PuLSe RADiATiONPurpose. Improving reliability of the technique to determine sensitivity of explosives to laser pulse radiation involving the method for defining function of energy distribution in a laser beam.Methodology. Experimental studies, physical and mathematical modeling.Findings. The available techniques to determine sensitivity of explosives to laser pulse radiation have been analyzed. The tech nique to define the function of energy distribution in a laser beam is rather simple not requiring complex experimental equipment.Originality. Regularities of energy density distribution within the laser ray crosssection have been determined. It has been demonstrated that both theoretical and experimental dependences of energy density upon the laser ray radius are characterized by Gaussian distribution being little different from each other. Changes in radiation intensity within the laser ray crosssection have been determined experimentally.Practical value. Practical use of the laser initiation technique is connected with the improvement of the known methods to develop profiled detonation waves within the explosive charges as well as plane, cylindrical, conical, and spherical shock waves in different materials. Methods to develop such waves are characterized by maximum high repeatability of results and high efficiency in terms of minimum possible power consumption.

Purpose. Theoretical and experimental research on the structural and strength peculiarities of the backfill mass formation during the ore deposits development by activating the binding material of the backfill mixture using fine grinding at the stage of its preparation. Methods. An integrated methodological approach is used, consisting of laboratory studies on determining the properties of backfill mixtures and the structural internal bonds of the backfill mass using scanning electron microscopy. Some laws of the binding material chemistry are used and systematized in the course of theoretical research. Findings. Based on theoretical and experimental research, the interaction and the hydration products of the backfill mixture binding components with water have been studied. The use of a finely ground combined binding material made of slags and limestone improves and strengthens the structural bonds of the backfill mass through a large gap in the covalent bonds of silica and slags, the transition of ions of a weak ionic bond to the formation of other compounds and equalizing the ratio of Si and Са ions in solution. Originality. It has been determined that with an increase in the specific surface area of the binding material particles, the shape of structural new formations of the backfill mass improves, has high strength, and the basicity of its new formations increases. Practical implications. Using the results, it is possible to rationally choose the binding material dispersion, obtain high strength of the backfill mass and increase the stability of its outcropping.

Цель. В данной работе предполагается исследовать влияние условий и параметров микроволнового излучения на изменение физико-механических свойств строительных материалов, в частности оценить стабильность их прочностных характеристик. Методика. Были использованы следующие методы: исследование влияния СВЧ-нагрева на кинетику свойств изделий; определение предела прочности растворов и бетонов на сжатие; сравнительный анализ. В качестве образцов были избраны цементно-песчаные кубики размером 5×5×5 см, изготовленных согласно ДСТУ Б В.2.7-187:2009, с выдержкой для приобретения ими марочной прочности в течение 28 суток. Результаты. Эксперимент заключался в определении влияния мощности СВЧ-излучения и продолжительности его воздействия на изменение прочностных характеристик сухих (естественной влажности) образцов и образцов, насыщенных водой. В ходе эксперимента было проведено испытание на прочность при одноосном сжатии сухих и насыщенных водой образцов, предварительно подвергнутых воздействию СВЧ-излучения (минимальной, средней и максимальной мощности) в диапазоне времени от 1 до 3 мин. Наибольшие разрушающие воздействия СВЧ-излучения на цементно-песчаные образцы достигнуты при значениях мощности от 500 до 900 Вт и продолжительности 2-3 мин. Научная новизна. В данной работе исследовано влияние мощности СВЧ-излучения и продолжительности его воздействия на процесс разрушения цементно-песчаных образцов. Практическая значимость. Установлено, что обработка материалов СВЧ-излучением облегчает процесс их разрушения. Предложенная технология позволит получить научную базу для использования СВЧ-излучения с целью разрушения не только бетона и других строительных материалов, но и горных пород. Также перспективным направлением является изучение обратной задачи-применение СВЧ-излучения при растворении бетонной или другой строительной смеси водой, что в дальнейшем, после ее затвердевания, приведет к повышению прочности изделий. Ключевые слова: СВЧ-излучение; образцы цементно-песчаных кубиков; эксперимент; мощность излучения; прочность; процесс разрушения Наука та прогрес транспорту. Вісник Дніпропетровського національного університету залізничного транспорту, 2019, № 3 (81) ТРАНСПОРТНЕ БУДІВНИЦТВО Creative Commons Attribution 4.