AN ASSESSMENT OF STEMMING TECHNIQUES AND THE PERFORMANCE OF STEMMING PLUGS IN BENCH BLASTING OPERATIONS IN PAKISTAN

This research article presents a comparative analysis of stemming techniques and the performance of stemming plugs in bench blasting operations, based on a case study carried out in cement quarries in Pakistan. For image analysis, the Wip-Frag software is utilized in order to demonstrate the benefits of stemming plugs over traditional methods. Real-time images captured during blasting at various cement quarries reveal a substantial presence of boulders within the muck pile when using conventional stemming materials such as drill cuttings and clay. This typically requires additional time and costs for secondary drilling, blasting, or hydraulic hammering. Blast test results indicate that stemming plugs improved the throw and shape of the muck pile and significantly decreased the boulder percentage. This study also compares the results of Wip-Frag software with sieve analysis of drill cuttings, indicating potential limitations in the software's reliability for particle size distribution. These results contribute to improving blasting operations and emphasize the importance of proper stemming techniques. improving blasting efficiency, the use of stemming plugs can potentially minimize operational costs and improve overall performance.


INTRODUCTION
Mining is an important economic sector in any country [1].Open cast mining, open pit mining, and underground mining methods are commonly used to extract valuable mineral resources [3].Most economic mineral deposits are found in massive hard rocks, which need to be fragmented to extract valuable materials and separate them for further processing [4].Rock blasting through drilling and blasting is the most common and efficient technology used in all mining operations throughout the world.[5].Bench blasting is a critical operation in mining, playing a vital role in attaining efficient mining processes [6].
Bench blasting success depends on a number of variables, including the type and amount of explosive used, powder factor, delay system, rock geology, blast pattern, burden and angle, depth and diameter of blast holes, stemming material and length of stemming [7].Fragmentation is a key outcome of bench blasting, as the fragmented muck pile is loaded and transported to crushers for further size reduction [8].Stemming is also a vital feature of bench blasting, influencing the 55 J. mt.area res., 9,2024 overall efficiency and effectiveness of the process [9].Stemming material is used to confine the gases generated during the blast, facilitating efficient energy transfer to the rock mass [10].Effective stemming leads to improved rock breakage, reduced fly rocks, reduced ground vibrations, and well-formed muck piles [11].Conventional stemming methods usually involve a mixture of soil and drill cuttings [12].However, dry drill cuttings have limitations in providing sufficient resistance to explosion gases, resulting in energy wastage [13].Several engineering solutions have been proposed to improve bench blasting operations and address stemming challenges.These include the use of air plugs, stemming plugs, small inflatable balloons, plaster of Paris packing and grouting to confine explosion gases in drill hole columns [14].In Pakistan, limestone quarries supply raw material to the cement industry, with 24 quarries discovered for this purpose [15].
Given the economic importance of bench blasting in limestone quarries, it is crucial to investigate current stemming practices and evaluate the performance of stemming materials and stemming plugs [16] To evaluate the particle size distribution of the drill cuttings, 1 kg samples of drill cuttings were collected from each quarry and subjected to sieve analysis using Tyler series sieves ranging from #4 to #65 (mesh), along with a pan sieve for all samples.In addition, pictures of the blasted muck pile were taken at each quarry site for later examination using WipFrag software to analyse rock fragmentation.The data gathered is summarized as follow: Table 1: Blasting parameters of the selected quarries.

RESULTS AND DISCUSSION:
After blasting, the captured photos were analyzed using WipFrag software to assess fragmentation performance.Figure 1 shows the results from Quarry 1.In WipFrag software, a reference object is required to provide the clear understanding of the fragmented rock; therefore, a person standing at the field was

VALIDATION OF IMAGE ANALYSIS TECHNIQUE:
In order to improve work processes,  The sieve analysis result showed varying percentage of drill cuttings in different size ranges.However, the WipFrag software results showed significant disparities.The WipFrag software was not able to detect sizes smaller than 0.5 mm, displays 0% in that range which is inaccurately.It also improperly indicated that only 0.19% of the drill cuttings were smaller than 1 mm in Sample 1, and 0.24% in Sample 2. Furthermore, comparing D50 results revealed differences between sieve analysis and software findings, with the graph (Figure 14) and (Figure 15) illustrating noticeable deviations in the results.Additionally, in Sample 3, the software failed to detect or measure the drill cuttings smaller than 1 mm, displaying 0% in that range, resulting in errors.
The D50 comparison indicated significant deviations between sieve analysis and software results, with the graph (Figure 16) indicating differences in the outcomes.
Similarly, the software results for Sample 4 deviated significantly from the sieve analysis, with only 0.77% of drill cuttings shown to be

3. 2
Installation of Vari-stem Stemming plug in blast no 3 and 4: To evaluate the performance of the varistem stemming plug, two blast tests were conducted at Quarry 3. The stemming plugs used in the tests are shown in Figure 5.

Figure 11
Figure 11 reveals that 23% of boulders are present in the muck pile, and most of the rock fragments lie between 200 mm to 400 mm.
as image analysis technique, to evaluate rock fragmentation in the mining industry.This approach involves capturing images of the fragmented rocks and using specialized software like WipFrag to generate graphs correlating particle size with percent passing.In this study, the WipFrag software was used, a recently developed granulometry tool (Maerz et al., 1996), to measure fragmentation from digital images of blasted muck piles.To ensure accurate size calculations, an object of known length was placed on the muck file for reference.The images are then imported into WipFrag, where fragment edges are identified and manually refined through netting, providing volume and weight measurements illustrated in the graph.However, issues have been raised about presenting the full muck pile with a 2D image and the accuracy of the data acquired.To address these concerns, the drill cuttings (stemming materials) were also collected from various cement quarries and subjected to further analysis.Additionally, sieve analysis was conducted to validate the particle size distribution results from the image analysis software.For this process, 1 kg samples of the drill cuttings were collected from four cement quarries in Punjab, Pakistan, and photographs were taken with a reference object for size reference and subjected to WipFrag.The WipFrag software was then used to generate graphical results from the photos.The sieve analysis was performed using Tyler series sieves in order to determine and validate the particle size distribution.A comparison between sieve analysis and software results was made, and variations were assessed and discussed.The findings were thoroughly investigated, revealing conclusive results.

smaller than 1
mm compared to the actual value of 52.8%. in Figure 17, The D50 comparison showed more disparities, as the software indicated 50% of drill cuttings smaller than 4.4 mm, not matching the sieve analysis results of 1 mm.These findings indicate the importance of carefully considering the software's limits and possible errors when determining drill cutting sizes in quarry operations using image analysis techniques.CONCLUSIONS This study examined the blasting operations conducted at various cement quarries and identified typical issues, such as higher percentages of boulders, poor throw, processes like secondary drilling and blasting or hydraulic hammering were required to break up the boulders separately.As a result, downstream operations will face increased unit costs.These additional expenses further increased the entire operational budget.In comparison, experimental work involving the use of stemming plugs demonstrated significantly improved blasting outcomes compared to conventional practices.Stemming plugs resulted a lower percentage of boulders, improved the muck file throw, and shapes.These positive effects of stemming plug directly influenced downstream processes such as crushing, hauling, and loading, enhancing their efficiency and effectiveness.Based on the findings, it is strongly recommended that quarry managers adopt the use of stemming plugs for stemming purposes.This practice has the potential to enhance blasting results by reducing boulder percentages, improving throw, and achieving desirable shapes of muck pile.These improvements can significantly impact various operational processes downstream, ultimately resulting in cost savings.Additionally, this investigation study revealed significant concerns regarding the use and reliability of the WipFrag software for the evaluation of rock fragmentation.The software has limitations in detecting particles smaller than 0.5 mm in size and consistently provided results that were larger compared to sieve analysis measurements.Such inconsistencies undermine the software's reliability and its usefulness in determining particle size distribution.Therefore, it is advised to explore and utilize alternative techniques that can ensure precise and accurate evaluation of particle size distribution, regardless of the practice size constraint.