Abstract
With the progress of deep mining in mine exploitation, the effect of the in situ stress field plays a more and more significant and crucial role in rock blasting. To uncover the impact of in situ stress field on empty-hole effect during parallel-hole cutting, the distribution and the trend of changes in dynamic stress around empty hole during blasting under different in situ stress conditions are simulated based on the basic model for parallel-hole cutting using 3D finite element analysis software ANSYS/LS-DYNA and implicit-explicit analysis method. Subsequently, the law of variation in the empty-hole effect under different in situ stress conditions is determined, and the effects of horizontal and vertical stress fields are analyzed in detail. The simulation results show that the overall increase in in situ stress can facilitate compressive failure and inhibit tensile failure in the rock mass around an empty hole during blasting. When empty holes are arranged horizontally, the effect of the vertical stress field is consistent with that of the in situ stress field, while the effect of the horizontal stress field is opposite to that of the in situ stress field. With the increased stress, the inhibitive effect of the vertical stress field on tensile stress around an empty hole is remarkably stronger than that of the horizontal stress field. Finally, the numerically simulated results are verified by the theoretical calculation. This study can provide new insight and a simple but accurate numerical simulation method to investigate how the in situ stress field affects the empty-hole effect, especially in deep mining.
Highlights
With the depletion of mineral resources in the shallow, their exploitation progressively deepens into the Earth [1, 2]
The distribution of and the changes in stress around empty holes under different in situ stress conditions during parallel-hole cutting are identified through numerical simulation based on literature [15]. e numerical simulation is carried out using ANSYS/LS-D YNA and implicit-explicit analysis method. e implicitexplicit analysis is a special computational analysis method embedded in ANSYS/LS-DYNA, which can simulate and reproduce linear static and nonlinear dynamic combined stress loading patterns
The distribution and the trend of changes in dynamic stress around the empty hole under different in situ stress conditions during blasting are effectively simulated using ANSYS/LS-DYNA software and implicit-explicit analysis method. e conclusion to this study can be summarized as below [11, 18]: (1) e results of numerical simulation indicate that the overall increase in in situ stress can inhibit the tensile failure of rock mass near the wall of the empty hole and facilitate the compressive failure of the same rock mass
Summary
With the depletion of mineral resources in the shallow, their exploitation progressively deepens into the Earth (normally up to 1000m) [1, 2]. The average depth of metal mines in South Africa has reached 2000 m, the Western Deep Level gold mine has reached 4800 m [3], and the borehole has reached 6779 m in the Baltic Shield [4]. In such extreme deep mining, some deemed as negligible problems in shallow depths turn to be very crucial and intractable, i.e., high stress, high temperature, high water pressure, and the disturbance resulted from mining activities, which may lead to sudden and unpredictable destruction of the rock mass [5,6,7,8].
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