Cable-bolt failures due to stress corrosion cracking (SCC) could significantly compromise the sustainability and long-term stability of underground constructions. To fully understand the SCC of cable bolts, a two-step methodology was implemented: (i) long-term cable-bolt coupon tests using mineralogical materials collected from underground mines; and (ii) accelerated full-scale cable-bolt tests using an acidified solution. In the long-term tests, a novel three-point bending coupon was designed. The effects of mineralogical materials on SCC were evaluated under the simulated underground bolting conditions through the application of “corrosion cells”. For accelerated tests, SCC resistance of different type of cable bolts was examined using the new designed tensile-loading apparatus under the periodically increasing strain-rate loading mechanism. It was identified that mineralogical materials and applied stress intensity accelerated the corrosion process of the cable bolts. The number of wires and wire surface conditions in different types of cable bolt directly affected SCC susceptibility. The cable bolts with a greater number of wires provided higher resistance to SCC. The developed experimental methodologies can be applied to study SCC in other reinforcement materials and the results can be used to design optimal support systems in different environmental and geotechnical conditions.

Cemented high-concentration backfill (CHB) is an indispensable solution for mitigating risks associated with underground mining voids and surface tailings ponds. The accurate prediction of pressure drop of CHB in pipe flow is crucial for the design of backfilling systems. In this study, full factorial loop tests were conducted to obtain observed pressure drop data and rheological parameters of CHB, while considering the variables of binder content, solid fraction, and flow velocity. The rheometer method was also utilized to acquire the rheological parameters of CHB for comparison. Three analytical models and one numerical simulation method, which are considered highly accurate in the literature, were employed to predict the pressure drop of CHB in pipe flow. The findings indicate that the Buckingham model and the Darby–Melson model produce identical results as they are fundamentally equivalent. The Swamee–Aggarwal model and the single-phase flow simulation employ a similar mechanism as the Buckingham model, albeit with minor variations in mathematical treatment. The rheological parameters of CHB obtained through the rheometer method are considerably greater than those acquired by the loop test method, leading to significantly higher predicted pressure drop values from both the three analytical models and single-phase flow simulation when compared to the measured values. Whereas the mean deviation of the three analytical models is within 6.5% when employing rheological parameters of CHB determined by the loop test, with the Swamee–Aggarwal model being the most accurate, the mean error of single-phase flow simulation remains within 10%. It is suggested that the rheological parameters of CHB be determined through small-diameter loop testing. The Buckingham model and single-phase flow simulation are subsequently recommended for predicting pressure drop in industrial straight horizontal pipelines and complex piping systems, respectively. The results of this study facilitate the selection of the simplest method for accurately predicting the pressure drop of CHB in pipe flow.

The stability of underground goaf in filling mining is dominated by the interaction mechanism of the backfill-surrounding rock combination. In order to investigate the interaction mechanism and failure characteristics of the backfill-surrounding rock combination, backfill-red sandstone combinations with three different cement–sand ratios were prepared for uniaxial compression tests. The deformation and failure characteristics of the specimens were analyzed. It was found that at the cement–sand ratio of 1:4, the backfill and red sandstone interacted with and restricted each other, and the through cracks appeared in the whole specimens, which indicated that the backfill and red sandstone can jointly resist external loads and play a role in common bearing. However, with the decrease of the cement–sand ratio, the stress mainly acts on the backfill, and the deformation observed in the backfill is large while there is no obvious rupture in the rock. Based on the failure characteristics and the stress–strain curves of the specimens, the damage constitutive relationship that can describe the failure process and deformation characteristics is proposed. Correlated with the experiment results, the damage constitutive equation is established in three stages including compaction pre-synergy stage, quasi-elastic synergy deformation stage and rupture deformation stage. The failure characteristics observed in each stage are analyzed. The research results are of great significance to accurately understanding the interaction between backfill and surrounding rock, which can be used to design and select the mixture ratio of the filling materials.

With the advancement of backfill mining technology, cemented high-concentration backfill (CHB), composed of solid particles, such as high-concentration tailings or waste rock mixed with a small amount of binder, has gained widespread applications due to its superior filling performance. Given the complexity of the backfill pipeline network, studying the characteristics of pipe transportation is crucial. The local resistance in bending pipes represents an important parameter for CHB pipeline transportation. However, existing research on the local resistance characteristics of bending pipes lacks comprehensiveness and depth. This study proposes a novel definition of the local resistance coefficient as the ratio of pressure loss per unit length of a bend pipe compared to that of a straight pipe. Utilizing the computational fluid dynamics (CFD) method the impact of six different factors on the local resistance coefficient of the bending pipe is investigated: flow velocity, pipe diameter, slurry concentration, binder content, turning radius, and bending angle. The results indicate that the local resistance coefficient positively correlates with the flow velocity and pipe diameter but negatively correlates with the slurry concentration, turning radius, and bending angle. Among these factors, the slurry concentration exerts the most significant influence on the local resistance coefficient. The recommended approach to control the local resistance coefficient in the mine is to use CHB with a 76% solid fraction at a 1.5 m/s flow velocity, along with pipe parameters of a 0.15 m diameter, a 2.5 m turning radius, and bending angles between 90° and 150°. The findings provide a valuable reference for determining the optimal parameters for bend pipes and CHB and facilitate the theoretical calculation of resistance in complex filling pipeline networks.

In the context of deep mining and green low-carbon transition, this study characterizes the thermo-mechanical evolution and fracture mechanisms of cemented tailings backfill (CTB) through systematic experiments conducted at 20–60 °C across 3–28 days. Results demonstrate that strength and elastic modulus follow a unimodal dependence on temperature, peaking at 40 °C. Gaussian modeling reveals that curing times narrow the thermal tolerance window, with the elastic modulus exhibiting higher sensitivity to overheating. A consistent “pre-peak activity window” is identified in AE responses, characterized by b-value drops and an increase in tensile event proportions from 66% to 83%. A composite AE damage index (ADI) is introduced to systematically precede macroscopic failure, with thresholds of ADI ≥ 0.60 and 0.70 indicating accelerated crack propagation and imminent instability, respectively. Microstructural analysis confirms that 40 °C promotes C-S-H and fine ettringite bridging, whereas temperatures ≥ 50 °C induce Ca(OH)₂ coarsening and enhanced pore connectivity, triggering early tensile-dominated degradation. This study establishes a “temperature → hydration/porosity → AE response → mechanical evolution” pathway, providing an optimal curing window of 40 ± 5 °C and an ADI-based early-warning criterion for temperature-adaptive CTB design and on-site safety management.