In a limestone aggregate quarry, excessive fines generation following blasting was primarily caused by extensively developed joint fractures and prolonged implementation of continuous coupled charging configurations. To minimize the generation of blasting fines and improve rock fragmentation, a small-diameter charge technology was developed based on the principles of decoupled charge blasting. Firstly, a fragmentation-damage correlation model for blast-induced fractured rock mass was developed in ANSYS/LS-DYNA based on field-collected measurement data. Secondly, numerical simulations were conducted to evaluate the blasting performance of the small-diameter charge structure relative to traditional decoupled charge methods, thereby confirming the technical viability of the proposed small-diameter charging approach. Thirdly, numerical simulations were conducted to determine the correlation between segmented small-diameter charge lengths and fines generation rates, thereby enabling technical optimization. Finally, field verification tests were conducted in accordance with simulation findings to assess the performance of the refined small-diameter charging method. Numerical simulations demonstrate that the small-diameter charging technique provides superior control over rock fragmentation, with the optimal dust reduction achieved using a dual-segment 2.0 m small-diameter charge configuration. Field tests demonstrate that employing a dual-segment 2.0 m small-diameter charge configuration reduces blasting fines generation by 6.53 percentage points compared to conventional continuous coupled charging, while maintaining comparable boulder yield, offering practical guidance for similar aggregate quarry operations.

In order to study the dynamic mechanical response characteristics of crystalline graphite ore under the coupling effect of grade and dynamic load, the dynamic compression tests of crystalline graphite ore samples with four grade levels (5.19%, 10.79%, 12.65%, and 15.50%) under different impact pressures were carried out by using a 50 mm diameter split Hopkinson pressure bar test device. The effects of grade and strain rate on the dynamic mechanical properties and energy consumption characteristics of crystalline graphite ore were comparatively analyzed. Furthermore, a dynamic constitutive model for crystalline graphite ore incorporating both grade and strain rate effects was established based on the viscoelastic ZWT model. The test results show that the dynamic compressive strength and peak strain of crystalline graphite ore increase progressively with rising strain rate, while the elastic modulus remains strain-rate-independent. As the ore grade increases, the initial compaction deformation and peak strain of the samples increase, whereas the dynamic elastic modulus, dynamic compressive strength, and their strain-rate sensitivity gradually decrease. Additionally, within a specific strain rate range, the degree of fragmentation of medium- and low-grade ores intensifies with increasing energy consumption density. In contrast, high-grade ores exhibit minimal variation in fragmentation degree. This indicates that ore grade significantly influences the dynamic fragmentation behavior of crystalline graphite ore. A dynamic constitutive model that considers both grade and strain rate was established, and its accuracy and applicability were verified by comparing the model-predicted results with experimentally obtained dynamic stress-strain curves. The model offers theoretical support for investigating the mechanical behavior of crystalline graphite ore under dynamic loading.

In order to study the crushing energy dissipation characteristics of graphite ore rock under impact loads, ϕ 50 mm diameter split Hopkinson pressure bar(SHPB) test device is used to conduct impact compression tests. The crushing energy dissipation law of the graphite ore rock samples is analyzed under different loading rates with five different impact pressures from 0.2 MPa to 0.6 MPa with a 0.1 MPa interval. The test results show that the dynamic compressive strength of the samples have a strong third-order polynomial relationship with the average strain rate under impact loads. The graphite ore rock has dynamic hardening under impact loads, and its dynamic compressive strength increases nonlinearly with the increase of strain rate, which shows an obvious strain rate effect. In addition, there is an obvious logarithmic relationship between the crushing dissipation energy and the incident energy. With the increase of incident energy, the crushing dissipation energy also increases. However, the proportion of the crushing energy gradually decreases from 0.38 to 0.11. The crushing energy dissipation density of the samples has an obvious strain rate effect, and its value increases with the increase of strain rate. Besides, the average particle size of the broken samples is strongly correlated with the energy dissipation density of the samples. As the energy dissipation density increases, the crushing degree of the sample becomes more severe. Therefore, the average particle size of the crushing fragments can be used to quantitatively describe the crushing degree of the samples.

The authenticity of fracture distribution model is one of the key factors during numerical simulation of blasting in jointed rock mass, which would obviously affect the numerical simulation results. It is hard to represent the complex three-dimensional joint distribution in the existing joint construction method. To explore a simple and feasible operation method for constructing the complex 3D joint model in LS-DYNA software, a K file of blasting numerical model was analyzed and reorganized by MATLAB software. Furthermore, a 3D refined numerical model for jointed rock mass was constructed by the 3D joint distribution law and the constitutive joint model parameters. Finally, a statistical analysis of the three-dimensional joint distribution law was carried out in an open-pit limestone mine, and the joints were reconstructed in the numerical model of a bench blasting. Consequently, a comparative study of the numerical simulation and the field blasting test for open-pit bench blasting was carried out. The results show that the error between the joints built in the numerical model and the actual joints is less than 13%. The joint surface changes the damage distribution of the rock mass. Compared with the intact rock mass, the damage rock mass range increases by 12.04%, and the proportion of fragments with the size of 0~100 mm decreases by 8.11%. The damage results obtained by blasting simulation are close to the field rock breaking effect, and the percentage error of fragments with the size of 0~100 mm is 4.16%. The analytical reconstruction method is feasible and easy to represent the complex three-dimensional joint distribution, and the numerical results are close to experimental results.