Key Takeaways & Executive Findings
- •• Incorporating steel slag into cemented paste backfill improves plastic behavior and reduces brittleness, making the stress-strain response smoother as the slag content increases. • At an interface angle of 45°, the composite exhibits a bimodal stress-strain curve and failure shifts from Y-shaped fractures to interface and axial splitting. • Steel slag reduces hydration products (e.g., Ca(OH)2) and increases harmful pores, weakening bond strength; thus, the recommended slag content should not exceed 45%. • Increasing the interface angle lowers the strength of rock-backfill composites, and the critical interface slip angle first decreases then increases with the ES/ER ratio.
Abstract
Abstract: The stability of the “surrounding rock-backfill” composite system is crucial for the safety of mining stopes. This study systematically investigates the effects of steel slag (SS) content and interface angle on the strength and failure characteristics of rock and SS-cemented paste backfill composite specimens (RBCS) through uniaxial compression strength tests (UCS), acoustic emission systems (AE), and 3D digital image correlation monitoring technology (3D-DIC). The intrinsic mechanism by which SS content influences the strength of SS-CPB was revealed through an analysis of its hydration reaction degree and microstructural characteristics under varying SS content. Moreover, a theoretical strength model incorporating different interface angles was developed to explore the impact of interface inclination on failure modes and mechanical strength. The main conclusions are as follows: The incorporation of SS enhances the plastic characteristics of RBCS and reduces its brittleness, with the increase of SS content, the stress−strain curve of RBCS in the “staircase-like” stage becomes smoother; When the interface angle is 45°, the RBCS stress−strain curve exhibits a bimodal feature, and the failure mode changes from Y-shaped fractures to interface and axial splitting; The addition of SS results in a reduction of hydration products such as Ca(OH)2 in the backfill cementing system and an increase in harmful pores, which weakens the bonding performance and strength of RBCS, and the SS content should not exceed 45%; As the interface angle increases, the strength of RBCS decreases, and the critical interface slip angle decreases first and then increases with the increase in the ES/ER ratio. This study provides technical references for the large-scale application of SS in mine backfill.
1. Introduction
Cemented paste backfill (CPB) is an important component of achieving green, safe, and scientific mining in mines, which can solve the subsidence problem of surface and underground mines, and improve the recovery of mineral resources [1 −3]. During the backfilling process, the CPB usually forms a composite structure with the surrounding rock of the upper and lower plates (Figure 1), and compared to the mechanical behavior of the surrounding rock, the backfill appears to be much “softer”, and the differences in mechanical properties lead to the redistribution of stress between the CPB and the surrounding rock layers [4, 5]. The composite structure will be damaged, or even deteriorated and rendered unstable, under the influence of mining activities and the natural stress regime [6, 7]. Therefore, a deep understanding of the mechanical properties and failure characterization of the backfill body and the surrounding rock composite structure is key to any analysis of the stability of goaf and ensuring mine safety and productivity.
The stability of the composite structure of backfill and surrounding rock is directly related to the properties of the backfill. SS-CPBs are gradually being more widely used due to their advantages of low backfill cost and good filling performance. On the one hand, SS has a “microbead effect” that can reduce the demand for water from the slurry, improve workability, reduce the heat of hydration, and promote late-stage hydration reactions to increase the strength of the backfill [8−10]. On the other hand, the presence of f-CaO, f-MgO, and metallic iron in the SS causes volumetric expansion after hydration; however, for mine backfill, moderate expansion of the backfill material can improve the effect of roof caving, control ground pressure and surrounding rock deformation [11−13].
Loading authentic research manuscript (Pages 1–5)...
HAO Jian-shuai, ZHOU Zi-han, CHEN Zhong-hui, CHE Zeng-hui (2025). Failure behavior of rock and steel slag cemented paste backfill composite structures under uniaxial compression: Effects of interface angle and steel slag content. Journal of Central South University. https://doi.org/10.1007/s11771-025-6012-5
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the effect of steel slag content on the mechanical behavior of rock-backfill composites?
Increasing steel slag content enhances the plastic characteristics and reduces brittleness of the rock-backfill composite, making the stress-strain curve smoother. However, excessive slag reduces hydration products and increases harmful pores, weakening strength, so the recommended maximum content is 45%.
How does interface angle influence the failure mode of composite structures?
The interface angle significantly affects the failure mechanism. At an interface angle of 45°, the stress-strain curve exhibits a bimodal feature, and the failure mode changes from Y-shaped fractures to interface and axial splitting. As the interface angle increases, the overall strength of the composite decreases.
What experimental methods were used in this study?
The study employed uniaxial compression strength tests (UCS), acoustic emission systems (AE), and 3D digital image correlation monitoring technology (3D-DIC) to investigate the strength and failure characteristics of rock and steel slag-cemented paste backfill composite specimens.
Why is the stability of the surrounding rock-backfill composite system important for mining safety?
The composite system of backfill and surrounding rock is critical for the safety of mining stopes. Its instability can lead to goaf collapse, surface subsidence, and reduced mineral recovery. Understanding its mechanical properties and failure behavior is essential for designing stable backfill systems and ensuring mine safety.
Does the steel slag content influence the hydration products in cemented paste backfill?
Yes, the addition of steel slag reduces hydration products such as Ca(OH)2 and increases harmful pores in the cementing system. This weakens the bonding performance and strength of the backfill, which is why the slag content should be controlled within a reasonable range.
Related Technical Papers & Translations
Design and optimization of a high-efficiency distillation process for cellulosic fuel ethanol integrated with thermal coupling and molecular sieve adsorption
To address the challenges of high energy consumption and prominent costs in the traditional three-columns distillation process for cellulosic fuel ethanol, a distillation—molecular sieve coupling separation process is proposed. This process integrates a three-column (crude distillation column, first distillation column, second distillation column) system with a 3A molecular sieve adsorption deep dehydration unit. A thermal coupling network is constructed via differential pressure design (steam from medium/high-pressure columns as mutual heat sources, reboiler liquid waste heat for feed preheating), and molecular sieve adsorption conditions are optimized. The study first performs a thermodynamic consistency test on the ethanol—water system, determines optimal non-random two-liquid (NRTL) model binary interaction parameters via experimental data regression for Aspen Plus simulation. Aiming at minimum total annual cost (TAC), Aspen Plus is used to optimize process parameters (theoretical tray number, feed location, reflux ratio, side-draw position, etc.). Economic analysis shows this process reduces CO2 emission costs by 27.56%, TAC by 15.58% (to 5.123 × 106 USD·a-1), and increases ethanol purity to ＞99.6%, providing an effective solution for green, efficient separation.
A cohesion loss model for determining residual strength of deep bedded sandstone
Rock residual strength, as an important input parameter, plays an indispensable role in proposing the reasonable and scientific scheme about stope design, underground tunnel excavation and stability evaluation of deep chambers. Therefore, previous residual strength models of rocks established were reviewed. And corresponding related problems were stated. Subsequently, starting from the effects of bedding and whole life-cycle evolution process, series of triaxial mechanical tests of deep bedded s
Federated model with contrastive learning and adaptive control variates for human activity recognition
Recent attention to privacy issues demands a communication-safe method for training human activity recognition (HAR) models on client activity data. Federated learning (FL) has become a compelling technique to facilitate model training between the server and clients while preserving data privacy. However, classical FL methods often assume independent and identically distributed (IID) data among clients. This assumption does not hold true in practical scenarios. Human activity in real-world scena