## 3 Field Test Analysis and Delay Adjustment Under Vibration Control  
### Engineering Background  
The experimental site is located in a large open pit mine in the western region of Inner Mongolia, China. The average height of the bench is 14.5 m, with a slope angle of approximately 78\({}^{\circ}\). The deposit consists of alternating layers of iron ore, rare earth minerals, limestone, and mica, distributed within a long, band-shaped ore body. The ore body extends approximately 334.4 m in the north-south direction and reaches a maximum width of about 91.7 m in the east-west direction. Figure 4 shows the location of the test blast area and drilled holes. Different hole spacing and row spacing were designed based on the ore type. In the rock area, the hole spacing is 11 m \(\times\) 6 m, while in the ore area it is 8 m \(\times\) 6 m. The main holes are charged with 700-950 kg/hole, while the peripheral holes are charged with 500-600 kg/hole. The total charge for the 338 holes is 300 t. The holes are connected to the detonation network according to the \"V\" shape, and electronic detonators are used to initiate explosions hole by hole. The inter-hole delay is set to 100 ms and the inter-row delay to 80 ms. Figure 5 provides a schematic diagram of the detonation network and the location of the test holes. The initiation time interval between the test hole and other holes exceeds 200 ms in order to obtain a complete single-shot vibration curve, which serves as the reference curve for reconstructing the single-shot vibration curve at any arbitrary location. On the northern slope of the blasting area, two vibration monitoring lines were established, and the precise coordinates of seven monitoring points were obtained using GPS. Figure 6 illustrates the layout of the blast vibration monitoring points. Based on the coordinates of the monitoring points and blast holes, the propagation times of vibration waves from each hole were calculated, enabling the determination of the arrival time sequence of all hole waves at the monitoring points using Equation (2). Taking monitoring point B1 as an example, Figure 7 illustrates the arrival time distribution of vibration waves generated by 338 blast holes. In the figure, the \(x\)-axis represents the blast hole  
Figure 3: Omni-directional vibration control method for the blast area. number (sequenced by initiation order) and the _y_-axis indicates the wave arrival time (ms) at the monitoring point. To better visualize the temporal differences in wave arrivals from different holes, the data are divided into four subplots (Figure 7a-d) based on the initiation sequence. It should be noted that the dominant frequency obtained from Fourier transform analysis of the single-hole vibration waveform at monitoring point B1 was 9.94 Hz, with high-frequency components exhibiting significant attenuation during propagation from the blast source to the monitoring point. Consequently, the influence of medium dispersion characteristics on the propagation velocity of different frequency components was not considered in this study. The average wave propagation velocity, determined experimentally as 4.4 \(\times\) 10\({}^{3}\) m\(\cdot\)s\({}^{-1}\), was adopted to calculate the arrival times of blast-induced vibrations at the monitoring points. As shown in Figure 7, the arrival time sequence lasts for approximately 3600 ms. The arrival time sequence curve exhibits a sawtooth pattern rather than a smooth curve. This indicates that, within the same time interval, vibration waves from multiple holes reach the monitoring point simultaneously. The greater the number of vibration waves arriving at the same time, the greater the probability of influencing the superposition of vibration wave peaks and valleys to cancel each other out, making it easier to form the problem of larger vibrations. Figure 4: Location of the experimental blast area and drilled holes. Figure 5: Schematic of the detonation network and test blast hole locations.