To determine the dynamic demand for support design under rockburst conditions, one of the most important issues is the prediction of ground motion parameters at the site of interest. Field monitoring has shown that the peak ground motion at the surface of an excavation in fractured rock is preferentially amplified compared to the motion in solid rock at a similar distance from the source. However, the traditional scaling laws used in rock support design do not account for the effect of free surface (excavation) and fracturing of rock. Recent studies have shown that high ground motion might be generated when a seismic wave crosses through fractures near a free surface in fractured rocks which is very complex and is not well understood. In this paper, particle velocity amplification was theoretically studied by investigating the dynamic interaction between seismic wave and multiple fractures near a free surface using the method of characteristics and the displacement discontinuity model. A harmonic load was applied on a model with a fractured zone near a free surface to investigate this phenomenon. After the harmonic wave propagated normally through multiple parallel fractures, the velocity amplification factor (VAF) was calculated as a function of the ratio of the magnitude of the peak particle velocity at the free surface of the model to the peak input velocity. The VAF can be as high as 3.77 and varies depending on the state of the fractured rock and the characteristics of the seismic wave. Parameter studies were conducted to investigate the effects of seismic load and multiple fractures on wave propagation, especially in terms of the wave frequency, the fracture spacing, the number of fractures and the stiffness of fractures. The results have proved that the interaction of the seismic wave and multiple fractures near the free surface strongly influences the ground motion. Quantitative relationships between the various influential factors and the corresponding VAF were developed. It is anticipated that such relationships can provide criteria to improve the current design procedures and help mining engineers to improve their rock support practice for rockburst-prone areas.

The gravity flow behavior of blasted ore and caved waste in sublevel caving (SLC) mines is complex. The shape of fragmented ore and caved waste is identified as one of the principal factors influencing the gravity flow of ore. To investigate the effect of the particle shapes on the gravity flow, a code was developed to generate polyhedral fragments in different shapes and divide them into internal elements. Then these fragments were imported in the LS-DYNA code to generate SLC models containing blasted ore and caved waste and model the extraction process. To model the non-continuous loading process, the gravity flow was considered to be an intermittent process by setting a switcher at the extraction point. The flow behavior of ore from the numerical modeling is in agreement with the experimental results. The cumulative dilution of ore by waste is up to around 30%, which agrees with the results of the field survey.

Blasting is widely used in civil and mining engineering projects, with the side effect of introducing damage to the remaining rock. The damage can be differentiated from the cracks in the remaining rock, which increases the concerns of safety and requirements for rock support. In situ study of crack development remains complicated and costly; therefore, small‐scale blasting experiments are a viable alternative for a detailed investigation of the crack propagation behavior. To fill the gap, this study examined a small‐scale blasting test by investigating the velocity of the cracks implementing the digital image correlation (DIC) technique and avoiding contact methods such as strain gauges. An ultra‐high‐speed camera (UHSC) was used to record the blasting test in a single blasthole rock‐like sample with a PETN cord. The experimental design underwent calibration until achieving the configuration of the equipment while ensuring the safety distance. The developed experimental methodology was tested successfully capturing the crack behavior. The analysis outcomes showed that the raw UHSC data needed to be preprocessed to enhance the tracking of cracks with the DIC method. The findings of the DIC data analysis indicated a fluctuation in the propagation velocity along the cracks (889–1129 m/s), revealing that the proposed methodology positively contributes to the propagation behavior of using the DIC method to track the blast‐induced cracks.