Key Takeaways & Executive Findings
- •• Decreasing cement–tailings ratio reduces both compressive strength of CTB and shear strength of CTB–rock interface, while increasing failure area and reducing roughness of the new interface. • Digital image correlation identifies compressive stress concentration at obtuse angles relative to shear direction as the primary trigger for CTB failure. • Silicon particles are more prone to failure in wear areas, as confirmed by correlation between wear area and silicon-dense regions. • Findings support optimizing cement content in CTB design: lower cement can be used when horizontal principal stress is high, improving cost-efficiency and stability.
Abstract
The shear characteristics of the interface formed between a cemented tailings backfill (CTB) and surrounding rocks play a crucial role in the design and stability of underground goafs. To investigate the shear behavior of CTB–rock interfaces, rock samples representing the topography of surrounding rocks were constructed using 3D morphology scanning and engraving techniques. A series of direct shear tests were conducted on the CTB rock samples to examine the influence of the cement–tailings ratio on the interfacial shear behavior. The results showed that the compressive strength of the CTB and shear strength of the CTB–rock interface decreased with decreasing cement proportion. With deceasing cement content, the failure area of the CTB after the test increased, and the roughness of the newly generated interface reduced. A digital image correlation analysis revealed that the compressive stress concentration in the region with an obtuse angle with respect to the shear direction was the primary cause of CTB failure. Moreover, the correlation between the wear area and the silicon-dense area helped confirm that the silicon particles are more prone to failure in these areas than in other regions. Our findings provide new insights into the shear sliding mechanism at CTB–rock interfaces and can aid in the selection of the cement–tailings ratio at engineering sites. For example, if the horizontal principal stress of the surrounding rock mass in a backfilling area is relatively high, the cement content can be reduced for CTB applications.
1. Introduction
With the rapid evolution of human society, the safe and efficient underground extraction of mineral resources has become crucial. However, the rapid exploitation of these resources has resulted in significant challenges, including the instability of underground goafs, haphazard disposal of solid waste, and land subsidence, leading to unpredictable environmental pollution and economic losses [1–6]. Against this backdrop, the cemented tailings backfill (CTB) method has gained increasing attention in underground gold and nonferrous mines. In recent years, innovations in CTB mining processes have significantly broadened the application of backfill mining techniques. The CTB method not only ensures the stability of vacant areas but also efficiently utilizes the solid waste generated during mineral resource development [7‒15].
The introduction of CTB inevitably triggers interactions with the original “medium” of the quarry, comprising surrounding rock and pillars, forming a support system that collectively resists deformation [16–19]. The variation in the mechanical properties between the CTB and surrounding rock creates a potentially weak interface that is susceptible to destabilization, as shown in Fig. 1. With an increase in the mining depth and area, the stress environment becomes more complex, and the expansion of the gob area further exacerbates the risk of backfill instability. The shear behavior at the CTB–rock interface is particularly significant under conditions of increasing depth and high stress, which can lead to the formation of shear planes that compromise the structural integrity of the backfill [20‒22]. Consequently, investigating the uncoordinated deformation of the CTB–surrounding rock interface is pivotal to ensuring mining zone stability [23]. Furthermore, surface subsidence resulting from mineral resource development can exacerbate shear sliding between the CTB and the surrounding rock and ore body, culminating in severe failure [24]. For instance, the abrupt collapse of the CTB at section 978 m in the Jinchuan Ni–Co II Mine could be attributed to the significant compressive shear stresses generated at the CTB–rock interface due to ground subsidence [25]. Hence, understanding the shear behavior of the CTB–rock interface is essential for guaranteeing the stability of mining areas.
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Wenkai Ru, Diyuan Li, Hao Gong, Pingkuang Luo, Junjie Zhao (2025). Effect of the cement–tailings ratio on the shear failure mechanism at the cemented tailing backfill–rock interface: Insights from the morphology of stope surrounding rocks. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3108-8
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Frequently Asked Questions
What is the effect of cement-tailings ratio on the shear strength of CTB-rock interface?
The study found that decreasing the cement-tailings ratio reduces both the compressive strength of the cemented tailings backfill (CTB) and the shear strength of the CTB-rock interface. This is because lower cement content weakens the bonding between particles, making the interface more prone to failure.
How was the morphology of stope surrounding rocks incorporated into the study?
The researchers used 3D morphology scanning and engraving techniques to construct rock samples that accurately represent the topography of stope surrounding rocks. This allowed them to conduct direct shear tests on realistic CTB-rock interfaces and observe failure mechanisms under controlled conditions.
What role does digital image correlation (DIC) play in this research?
Digital image correlation (DIC) was used to analyze strain and stress distributions during shear tests. It revealed that compressive stress concentration in regions with obtuse angles relative to the shear direction is the primary cause of CTB failure, providing insights into the failure mechanism.
What practical recommendations does the study offer for engineering sites?
The study suggests that if the horizontal principal stress in the surrounding rock mass is relatively high, the cement content in CTB can be reduced. This can lead to cost savings while still maintaining adequate stability, as the failure mechanism is better understood.
What is the significance of the correlation between wear area and silicon-dense area?
The correlation indicates that silicon particles are more prone to failure in wear areas, which are regions of high stress concentration. This finding helps explain the micro-scale failure mechanisms and can guide the selection of materials to improve interface performance.
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