The stress wave generated by rock blasting causes vibrations in the off-contour massif. The rock strength is significantly reduced in those off-contour massif areas where the permissible velocity is exceeded. This can lead to the collapse of nearby ledges. The aims of the study are to develop a methodology for determining the boundary of the off-contour massif seismically hazardous zone, as well as to assess the well delay interval effect on the hazardous zone boundary position. Elastic vibrations of the off-contour rock under the effect of a blast wave are considered. The dependence of the rock mass displacement under the action of stress is a function of time and distance from the blast site. A series of production experiments were conducted at the “Valley” quarry of Amur Minerals JSC to determine the coefficients values that take into account the attenuation of the stress wave in the rock with increasing distance from the blast site. A method to determine the position of the off-contour massif boundary has been developed. Beyond that boundary the rate of rock displacement does not exceed the permissible value. The initial data for the calculation are the rock mass physical and mechanical characteristics and the parameters of the explosives used. In the Simulink environment a simulation model was developed to implement the described method. A methodology for energy assessment of the process of rock displacement under the effect of a stress wave was developed to verify the modeling results. By analy-zing the results obtained, a conclusion was made about the sufficient accuracy of the proposed method for practical calculations. Displacement energy values of the same point of the off-contour massif are compared at different well delay interval. Rock blasting with increased well delay intervals allows to improve the off-contour massif safety, as well as the overlying horizons ledges. The quality of blasted rock loosening is maintained.
Due to the insufficient accuracy of existing studies of frozen sedimentary rock cutting process for practical calculations, the article solves the problem of determining the tangential component cutting resistance for blocked, deep blocked and cell cutting, which are currently the most commonly used methods in earthmoving equipment. The cutting tool and rock mass force interaction is considered from the point of view of the emerging stresses, which act on the separated chip element. The analytical dependences for determining the tangential component of cutting resistance were obtained. The numerical explanation of the choice of cell cutting in relation to blocked and deeply blocked cutting is given. For all three methods of cutting, under equal geometrical parameters of the cutting tool and the physical and mechanical properties of the frozen rock, the numerical value of the tangential component of cutting resistance is obtained. The comparison of the cutting resistance estimated values has shown that cell cutting requires relatively less energy and is preferred during the process of frozen sedimentary rock excavation. During field and laboratory investigations with the use of a multi-purpose cutting stand, a sufficient convergence of the analytical statements with the physics of frozen sedimentary rock cutting process was established. The results of the research allow a more reasonable approach to the adjustment of existing methods for determining the required tractive force and power for the drive of an excavation machine, and, therefore, to the actual efficiency and profitability of work.
As a result of the analysis of the work on rock destruction by cutters of milling of machines, it was found that the existing developments do not allow us to proceed to the derivation of calculation d dependencies for determining fracture resistance, or can be used only in preliminary calculations of the known by design parameters of milling machines. To eliminate these disadvantages, a combined physical and mathematical model of the process of interaction of a single milling cutter with a spherical tip with the rock has been developed. Consideration of the physical picture of the action of forces and stresses acting from the cutter with spherical tips on the separating rock element in the limiting condition allowed to describe analytically the components of total resistance, which are the mathematical part of the physical and mathematical model of rock destruction by cutters. Analytical dependences for determining the tangential and normal components of fracture resistance of rocks of medium hardness have been obtained. The adequacy of the physical and mathematical model to the physical process of destruction of rocks of different hardness by cutters on a universal stand was tested both in the field and in the laboratory conditions. Technical evaluation of the results of experimental studies confirms the reliability of the developed physical and mathematical model.
