# The Role of Delays in the Performance of Blasting
###### Abstract  
When researching rock blasting, the design parameters typically used for analysis are the geometric and charging parameters. This study focuses on a different approach based on the effect of timing, specifically the role of delays in the initiation sequence. Data were obtained from the results of full-scale blasts. The experimental setting and location allowed us to consider all parameters, other than the number of delays, as constants. The experimental results were analyzed, relating the delay variables to the fragmentation and KPIs of downstream operations. It was found that increasing the number of delays per unit of blasted rock and reducing simultaneous adjacent holes produces finer fragmentation, reduces the amount of fines, facilitates secondary operations, and reduces the risk of flyrock.  
drill and blast; delays; timing; KPIs; mining +
Footnote †: journal: _Sci._  
0000-0001-8000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-00000-  
x50 was improved by approximately 25% at a delay time of 180 \(\upmu\)s. The results indicated a notable difference and substantial improvement in fragmentation when the delay times fell within the range of no-shockwave interaction. In Ref. [8], full-scale tests were conducted on short-delay blasting using electronic detonators to enhance the tensile effect of the stress wave tail. Field experiments revealed a 45.6% improvement in the mean size of fragments compared to blasts with longer delay times. The authors in [9; 10] proposed an analytical solution for predicting the supersonic detonation of a cylindrically shaped explosive charge, which is suitable for numerical methods. To validate the model, the authors conducted tests to investigate stress wave expansion from a detonating borehole and stress wave interactions with geological features such as discontinuities, interfaces, and cracks. Similar outputs were found by [11]. The research described in [12; 13] involved conducting tests in an open-pit limestone quarry, confirming that the right selection of delay timing can enhance fragmentation and, consequently, improve subsequent extraction processes. The study in [14] showed that energy consumption at the primary crusher is the sum of two components depending on the distribution of the muckpile: The energy used for mechanical crushing and the energy used for winning the inertial resistances. The limitations of electronic detonators were studied in [15], where it was commented that the delay time and initiation accuracy are not typical governing factors for blast performances. The author of [16] agreed with that of [15] in that interacting stress waves have a local impact that is insignificant at the scale of the volume of fragmentation; therefore, a very short delay does not generate significant changes in fragmentation. The experimental results obtained in [16] and the numerical results in [17] are in agreement with [15], showing no significative differences in fragmentation with shockwave interactions compared to that without shockwave interactions.  
This research investigates the role of delays and delay density in blasts using a full-scale experimental approach. The delay time remained constant at 42 ms, as explained in the next section. Therefore, this study focuses on the performance of different delay times and the interactions of shockwaves at different timings.