Due to the differences in mineral processing techniques, the grain-size of tailings used in the construction of a tailings pond is not commensurate. It has been determined that the hydrodynamic characteristics of mudflow resulting from the failure of tailings dams are directly influenced by grain-size, solids concentration, and the surface roughness of gully and impoundment geometry. However, the behavior and influence of the grain size of mudflow resulting from a tailings dam failure have not been sufficiently examined. To investigate the effect of grain size on the hydrodynamic characteristics of mudflow surging from tailings dam failure, the law of mudflow evolution, the change of dynamics pressure, and the velocity distributions of mudflow have been obtained via a series of flume experiments utilizing three types of grain size tailings (d₅₀ = 0.72 mm; d₅₀ = 0.26 mm; d₅₀ = 0.08 mm, respectively). This study proves conclusively that with an increase in grain size, the peak value of mudflow depth notably decreases in the same section. Furthermore, it has been noted that both the velocity and the dynamic pressure raise significantly, wherein the velocity displays two distinct primary stages; namely a rapid reduction stage and a slow reduction stage. This research provides a framework for the exploration of the effect of grain size on the hydrodynamics of slurry surging from a tailings dam failure, and all presented results provide an indispensable tool in terms of the accurate assessment of potential damage in the case of a prospective impoundment failure.

Adding a type of municipal solid waste (incinerator slag) into ultrafine tailings can effectively enhance the mechanical properties of tailings. With an aim to study the macro- and micro-mechanical properties of the tailings slag mixture (TSM), the strength parameters (internal friction angle, cohesion) and micro-mechanical properties with different slag contents were analyzed by geotechnical experiments and particle flow simulations, respectively. The macroscale experimental results demonstrated that the strength parameters of TSM were much higher than that of tailings. Strength parameters also showed non-linear-rising trends with increasing slag content. For the slag content of 40%, the maximum cohesiveness of TSM was determined at 65.2 kPa, and the corresponding friction angle was 39.9°C. Furthermore, the Particle Flow Code (PFC) micro-simulation software was used to analyze the micro-mechanical characteristics of the TSM at different slag contents. The microscale simulation outcomes indicated that the particle transport, particularly in their moving directions, became increasingly chaotic with an increase in the slag content; also, the slag particles significantly impacted the shear processing zone of the TSM. These experimental and numerical results brought more scientific insights into the shear failure mechanism of TSM.

The overtopping-induced lateral erosion breaching of tailings dams represents a critical disaster mechanism threatening structural safety, particularly in reinforced fine-grained tailings dams where erosion behaviors demonstrate pronounced water–soil coupling characteristics and material anisotropy. Through physical model tests and numerical simulations, this study systematically investigates lateral erosion failure patterns of reinforced fine-grained tailings under overtopping flow conditions. Utilizing a self-developed hydraulic initiation test apparatus, with aperture sizes of reinforced geogrids (2–3 mm) and flow rates (4–16 cm/s) as key control variables, the research elucidates the interaction mechanisms of “hydraulic scouring-particle migration-geogrid anti-sliding” during lateral erosion processes. The study revealed that compared to unreinforced specimens, reinforced specimens with varying aperture sizes (2–3 mm) demonstrated systematic reductions in final lateral erosion depths across flow rates (4–16 cm/s): 3.3–5.8 mm (15.6−27.4% reduction), 3.1–7.2 mm (12.8–29.6% reduction), 2.3–11 mm (6.9–32.8% reduction), and 2.5–11.4 mm (6.2–28.2% reduction). Smaller-aperture geogrids (2 mm × 2 mm) significantly enhanced anti-erosion performance through superior particle migration inhibition. Concurrently, a pronounced positive correlation between flow rate and lateral erosion depth was confirmed, where increased flow rates weakened particle erosion resistance and exacerbated lateral erosion severity. The numerical simulation results are in basic agreement with the lateral erosion failure process observed in model tests, revealing the dynamic process of lateral erosion in the overtopping breach of a reinforced tailings dam. These findings provide critical theoretical foundations for optimizing reinforced tailings dam design, construction quality control, and operational maintenance, while offering substantial engineering applications for advancing green mine construction.

Stabilized/solidified (S/S) sediments are eroded by dry–wet cycles (DWs) when applied in an atmospheric environment. The microporous structures of S/S sediments, including their size, shape, and distributions, are sensitive to DWs and closely related to their macro properties. Therefore, multiscale micropore measurements, including scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and nitrogen adsorption porosimetry (NAP), were conducted on S/S sediment samples subjected to different DWs to elucidate the micro-damage mechanisms of S/S sediments under DWs, in conjunction with unconfined compression strength (UCS) tests. The results indicated that, as DWs increased, the strength of the S/S sediments decreased, and pores/cracks developed due to the expansion of the calcium silicate hydrate (CSH) skeleton pore structures and the shrinkage of the sediment aggregate pore structures. Pores that accounted for most of the volume were those in the sediment aggregates in the range of 10² nm < d < 10⁴ nm (d represents the pore diameter), while smaller pores in the range of d < 10² nm contributed 90% of the pore area. Pores in the CSH skeletons (d > 10⁴ nm) increased with DWs, while those in the sediment aggregates decreased with DWs due to the expansion and shrinkage forces originating from the sediment particles with pore sizes of d < 10 nm. The plastic deformation of the pores in the CSH skeletons and sediment aggregates jointly controlled the strength of S/S sediments, and the adjustment of those pores gradually reduced the decrease rate of UCS. The revealed damage mechanisms of S/S during DWs provide theoretical foundations for optimizing S/S additives and expanding the engineering applications of the S/S sediments.

With the rapid expansion of high-speed railway (HSR) networks, the vibration impact on adjacent energy infrastructure has become a critical safety concern. However, existing research lacks a comprehensive evaluation of buried sour gas pipelines specifically in tunnel-undercrossing scenarios. This research investigates the dynamic response characteristics of a sour natural gas pipeline under train-induced vibration loads using a case study in Chongqing. A three-dimensional dynamic coupling model of the track lining soil pipeline system was established based on FLAC-3D. The study innovatively quantifies the vibration superposition effect during bidirectional train encounters and assesses safety using fatigue life and velocity thresholds. Results indicate that pipeline vibration is predominantly vertical. As train speed increases from 250 km/h to 350 km/h, the response exhibits a non-linear rapid growth within the 300–350 km/h range. Under bidirectional encounters, the peak displacement reaches 2.00 times that of unilateral passage, representing the most critical load condition. The maximum peak vibration velocity is 0.1 mm/s, far below the 2 mm/s safety threshold, ensuring structural integrity under current operational standards.

In high-concentration tailings backfilling, the stability of the backfill largely depends on the slurry’s self-weighted siltation behavior. Red mud—the strongly alkaline by-product of the Bayer process and a mixture of coarse and fine particles—requires a clear understanding of its self-weight settling–consolidation mechanisms to ensure safe and efficient backfilling. In this study, red mud slurry was selected as the research object, and a multi-scale approach combining sedimentation column tests and microstructural image analysis was employed to reveal the intrinsic relationships among the sediment layer height, sedimentation rate, and pore structure changes during self-weighted siltation. The results show that the flocculated structure of red mud slurry exhibits distinct stratification during self-weighted siltation, including a clarified layer, a structural transition layer, and a dense sediment layer. During the siltation process, the sediment layer height, sedimentation rate, and floc structure of red mud evolve nonlinearly. The addition of flocculants significantly enhances the formation rate of flocculated structures but increases the porosity of the sediment body. At the macroscopic level, this results in a shortened self-weighted siltation time and increased final sediment layer height. To describe the regulatory effect of flocculants on red mud floc structure, a macro–micro predictive model for the sediment layer height was established by introducing a structural enhancement coefficient, considering the effect of flocculants. The model achieved a prediction error within 16%. These findings provide theoretical support for structural control technologies and process optimization of high-concentration fine tailings backfilling, thereby contributing to the sustainable utilization of red mud and the development of environmentally responsible backfilling practices.