| Based on the Natural Science Foundation of China,aiming at the problems like low leaching efficiency and difficulty in recovery of the weakly weathered layer of Gannan ionic rare earth mine in the process of in-situ leach mining,the thesis puts forward a method of carrying out the small and air interval blasting in the weakly weathered layer and optimizing the pore structure by the blasting stress wave,to achieve the effect of "blasting-enhanced permeability".Based on this,the SHPB test is used to simulate the propagation process of explosion stress wave in weakly weathered granite of rare earth mine,to study the strength,deformation characteristics,propagation characteristics of stress wave and energy dissipation laws of rock samples under different impact loads.The research results in this thesis provide some theoretical support for the efficient mining of low-permeability rare earth ore bodies.The main contents and research results are as follows:(1)The effective porosity of weakly weathered granite ranges from 1.5%to 7%,and most of its initial effective pores are spherical with only a small proportion of crack.The static uniaxial compression test is carried out on the rock,and the strength and deformation characteristics of the rock under the natural-withering and saturated states are analyzed.The results show that water has great influence on the static strength and deformation of the rock,and the static average anti-compression strength of the saturated sample is 28%lower than that of the natural-withering state.Under the shock loading of moderate strain rate,the dynamic strength of both natural-withering samples and saturated samples has obvious strain rate effect,and the value exponentially increases with the strain rate.(2)The dynamic impact test of rock under different impact speeds is carried out.The results show that the stress wave characteristics of rock response obviously to the change of impact speed.With the increase of the impact speed,the amplitudes of incident wave and reflection wave are larger and larger.The amplitude of transmitted wave is greatly affected by the porosity of sample,and the amplitude of reflection wave is larger than that of transmission wave.The absorbed energy per unit volume of rock increases linearly with the increase of strain rate.(3)The cyclic impact test is carried out on the rock.The results show that the peak stress of the natural-withering and saturated samples decreases gradually and the peak strain increases gradually with the increase of times of shock.The law of crack growth is consistent before failure.The waveforms of the incident wave basically coincide with each other.The amplitude of reflection wave increases with the increase in the times of impacts,while the amplitude of transmitted wave decreases gradually,which is the rule at different impact speeds.The effective porosity of natural-withering and saturated samples decreases first and then increases with the times of impacts.The effective porosity of natural-withering samples changes dramatically during impacts,while the change trend of saturated samples is more gentle.(4)With the increase in the times of cyclic impacts,the absorbed energy per unit volume of natural-withering and saturated samples decreases first and then increases,and the various change trends are related to the impact speed and initial porosity.However,the absorbed energy per unit volume of natural-withering samples is more significant than that of saturated samples.The accumulated absorbed energy per unit volume of natural-withering and saturated samples increases linearly with the increase of accumulated effective porosity.With the decrease of impact speed,for natural-withering and saturated samples with different initial effective porosity,the slope of the relationship curve between their accumulated absorbed energy per unit volume and accumulated effective porosity is closer and closer.When the impact speed is 4 m/s,the slopes of the two curves are basically parallel. |
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