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The plane and axially symmetric 2D numerical modeling of rock mass blasting is carried out using the Lagrangian tensor-based method. The results are compared with the actual direct measurements of rock mass permeability in the near zone of underground nuclear explosion Dnepr-1 in Khibiny in 1972. The post-explosion permeability of hard rocks is assessable at an admissible accuracy using the calculated shear strain intensity. A case-study of rock mass permeability change assessment in the near zone of blasting of a complex configuration charge is discussed.

The gravity flow of granular materials in axially symmetric convergent channels (V-shaped bunkers) is analyzed using the discrete element method. The symmetrical radial flow becomes unstable under certain conditions, and a space-time structure forms in the medium. The flow becomes essentially nonradial and asymmetric - the material is discretized into blocks, and the field of velocities inside the material becomes discontinuous. Further deformation reduces to relative movement of the blocks as rigid bodies.

In this study, the swelling behavior of sand-bentonite mixtures and pure bentonite are investigated by considering different factors, such as bentonite content in the mixture, specimen preparation method by applying different compactive efforts, and varying effective stress levels. Compaction tests were performed on the specimens of the sand-bentonite mixtures with 10% and 20% bentonite contents and pure bentonite. The maximum dry unit weight and the optimum water content of the specimens with 20% bentonite were relatively higher than specimens with 10% bentonite. Pure bentonite specimens had a lower maximum dry unit weight and higher optimum water content compared to sand-bentonite mixtures. Specimens of the swelling tests were prepared at the optimum water content values. Up to a vertical effective stress of 25 kPa, the mixtures showed a swelling behavior. Under the effective vertical stresses of 50 and 100 kPa, it was evident that the specimens behaved in the compression side. It was seen that the application of either 10 or 25 blows by means of compactive effort in pure bentonite specimens had a neglectible effect on the swelling behavior.

The article describes the rotary drilling modeling using the two-mass system of a drill string with a crush-and-shear hybrid drill bit. The head resistance of rocks on the bit is determined non-linearly: the penetration rate is added with the strength loss in the supporting medium under impact. The scope of the analysis embraces the continuous force generated by the rotating bit and the pulsed impacts by the drill strings at the end-points of the bit-bottomhole detachment. The initial conditions of the post-impact process, which define the initial penetration rate and the speed of the bit, are determined with regard to potential stick-slip effects. The numerical modeling proves that, as against the torsional vibrations, the axial-torsional vibrations of the drill string often result in the chaotic dynamics of drilling.

In this paper, the effect of elevated thermal treatment on the physico-mechanical parameters of Chunar sandstone from Mirzapur district of U.P. was investigated. The studied area is represented geologically by the Vindhyan Supergroup from Meso to Neproterozoic age. Sandstone of Chunar area, Mirzapur, U.P. has been granted the tag of Geographical Indication (GI) under the category of natural goods in 2019. Mechanical strength tests (indirect tensile and uniaxial compressive strength) were performed by a universal testing machine. Samples were treated at elevated temperature in the electric furnace at different temperatures for conducting mechanical and physical tests in each sample and results were recorded. The results suggest that for sandstone, high temperature treatment leads to volume expansion, weight reduction and a decrease in density as well as the reduction in the strength characteristics. Up to 200°C there is an inappreciable increase in indirect tensile strength and compressive strength but after 200°C strength gradually decreases. Beyond 400°C, the P-wave velocities showed a sharp decline due to elevated temperature treatment induced cracks in the heated sandstone.

The strength, elasticity and deformability testing of cemented paste backfill is carried out. The test backfill compositions include fine and very fine natural sand with the increased content of clay and dust, and refined with sifted granular blast-furnace slag 0-5 mm in size. The uniaxial compression strength, elasticity modulus and Poisson’s ratio are determined in the test backfill compositions at different stages of curing. The ultimate uniaxial compression strength is correlated with the P-wave velocity and elasticity modulus determined in the static and dynamic tests of the backfill compositions.

In this paper, De Moura and Butt model is extended to the large diameter drilling applications. The model proved to be effective and highly accuracy in predicting drilling performance in 19 distinct RBM and TBM operations even in the presence of datasets with high dispersion.

The authors substantiate the design of an excavator’s end effector for joint rock crushing and loading. The structural layout and parameters of hydroimpactors included in the end effectors of mining machines are described. The physical model of the hydroimpactors is constructed, tested and adjusted. The test data on the dynamics and outputs of the model at different power fluid flow rates are compared. The simulation model of the hydroimpactor is constructed and verified using the test data. The capabilities of the hydroimpactors are calculated for the planned modes of operation. For the excavator’s end effectors, it is proposed to use the hydroimpactor design with the lagged return travel of the piston toward the flexible adjustment of the hydroimpactor performance and to reach the required impact capacity at lower flow rates of power fluids.

It is important to enable remote control of duty cycle of air hammers via external distributors meant to set impact frequency. A new general layout is developed for the air-driven impact impulse generator with smooth adjustment of impact frequency at constant energy in driving construction elements in soil. The experimental model of the machine is designed and tested. Based on the analysis of the impulse indicator diagrams of the machine duty cycle, the impact frequency is correlated with the piston choke cross-section for three configurations of the control unit. The impact frequency control limits are found.

The spotlight is on reversal ventilation in a mine in case of an accident in winter. The inlet of cold air in underground openings endanger the health of miners, and mining equipment suffers from an adverse effect of negative temperatures. In compensatory measures design, the source data is the potentially transient distribution of mine air temperature after airflow reversal. The procedure of air temperature pattern in ventilation shaft during airflow reversal involves mathematical modeling of transient thermal processes in the shaft and in adjacent rock mass. The correct choice of the heat transfer coefficient between the shaft lining and air results from the comparison of the modeling results and the experimental data on the air temperature dynamics in planned airflow reversal.