*Important notice: This news reports on an unedited version of an accepted paper and is awaiting final editing. Therefore, the paper should not be regarded as conclusive or treated as established information.
Researchers have examined how particle gradation and vibration intensity affect pore-water pressure in sandy mine waste. The researchers conducted laboratory shaking-table tests with four controlled sand mixtures. They also developed coupled seepage, dynamic, and slope-stability models to assess traffic loading at the waste-dump scale. The results showed that stronger vibration generally increased pore pressure during the first loading stage.
Study: Effects of particle gradation and vibration intensity on the pore water pressure response of sandy mine waste*. Image Credit: Ioanac/Shutterstock.com
Assessing Dynamic Stability in Sandy Mine Waste
Open-pit mine-waste dumps often contain materials with different particle sizes, sources, and compaction levels. These differences influence how waste responds to rainfall and repeated vehicle loading. Rainfall infiltration increases water content and alters pore-water pressure. In saturated or nearly saturated sandy materials, this loading can rearrange particles, increase pore pressure, reduce effective stress, and lower shear resistance.
Previous studies have examined rainfall effects, cyclic loading, liquefaction, and particle gradation. However, researchers have often investigated these factors separately. The combined response of sandy mine waste to rainy-season traffic loading remains insufficiently understood. This issue is important because waste dumps may experience water infiltration and repeated vehicle movement during normal mine operations.
The researchers focused on two main factors: particle gradation and vibration intensity. The study examined how traffic-induced dynamic loading could affect pore pressure and slope stability at the engineering scale. The research addresses a practical gap in mine-waste management. It connects laboratory observations of particle behavior with numerical predictions of waste-dump performance.
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Experimental Assessment of Four Sand Mixtures
The researchers prepared four sandy materials by varying the proportions of quartz sand and river sand. LS1 contained 100% quartz sand. LS2 contained 75% quartz sand and 25% river sand. LS3 contained 25% quartz sand and 75% river sand. LS4 contained 100% river sand. The mixtures had different particle-size distributions and uniformity coefficients. All four gradations fell within an empirical range associated with liquefiable sands.
The researchers prepared the specimens in a loose condition through underwater deposition. Initial relative densities ranged from approximately 31% to 34%. They placed the samples in a transparent cylindrical container with sealed boundaries, creating an approximately undrained testing environment. A miniature pressure sensor continuously measured pore-water pressure during vibration.
The researchers applied horizontal cyclic vibration at five peak accelerations. Each vibration lasted 5 seconds at 4 Hz. They applied three vibration stages to the same specimen and allowed a 0.5-hour interval between stages. They also measured changes in specimen height to assess densification and changes in relative density.
Researchers used SEEP/W, QUAKE/W, and SLOPE/W in GeoStudio 2025.2 for engineering analysis. They selected LS3 as the representative sandy-waste material. The model combined seepage, dynamic loading, excess pore-pressure development, and slope-stability analysis. Vehicle loads ranged from 20 to 100 kPa. Additional simulations examined 60, 80, and 100 kPa loads applied for 30 or 60 seconds.
Vibration Intensity and Particle Structure Influence Pore Pressure
All four sand mixtures developed excess pore pressure during cyclic vibration. During the first vibration stage, stronger acceleration generally produced higher peak pore pressure. In LS1, tests at 0.2g, 0.25g, and 0.3g reached or approached the study's common pore-pressure reference level.
The response changed during the second and third stages. Peak pore pressure didn’t follow a consistent increase with acceleration. Some tests showed an initial rise followed by a decline. The researchers linked this change to pore-pressure dissipation, particle rearrangement, and densification during earlier loading. At 0.30g, LS1 increased in relative density from 31% before the first stage to 57% before the second stage and 59% before the third stage. As particle density increased, the available pore space for further contraction decreased, limiting additional pore-pressure build-up.
LS1 had the lowest coefficient of uniformity (1.57), indicating a relatively uniform particle structure. This structure allowed greater particle sliding and contractive deformation. In contrast, LS3 had a broader particle-size distribution and contained smaller sand particles. These particles could occupy some of the available pore space and reduce further contraction. As a result, LS3 showed greater stabilization during later vibration stages.
The numerical model showed that stronger vehicle loading increased pore pressure across the waste dump. Raising the load from 20 to 100 kPa increased the 95th-percentile excess pore pressure from 3.79 to 24.29 kPa. High-pressure zones developed near the crest platform, slope shoulder, and shallow slope surface. The minimum factor of safety fell from 1.3006 to 1.2545, a 3.54% reduction. However, all cases remained above 1.0. Longer loading caused only limited additional reductions in stability under the model conditions.
Improving Mine-Waste Dump Stability Management
The study shows that particle gradation, vibration intensity, and loading history all influence sandy mine-waste behavior. The engineering results show that stronger vehicle loads increase excess pore pressure and reduce the factor of safety, particularly near the crest platform, slope shoulder, and shallow slope surface.
Future studies should focus on the rainy season’s impact on mine operators, drainage, material gradation, and traffic loading. Load and speed controls, improved drainage, optimized traffic routes, and targeted monitoring can help manage these risks. The study also highlights the need for further testing with repeated specimens and direct measurements of saturation and unit weight. Overall, the findings provide a practical framework for improving mine planning and managing sandy waste dumps.
Journal Reference
Deng, X., Li, X., et al. (2026). Effects of particle gradation and vibration intensity on the pore water pressure response of sandy mine waste.* Scientific Reports. https://www.nature.com/articles/s41598-026-68128-y
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