To address the stability challenges of non-circular openings in deep underground engineering, this study focuses on four common opening types in underground rock engineering-three-centered arches, squares, circles, and isosceles trapezoids-establishes a stress solution model and a discrete element numerical calculation model based on complex function theory, investigates the stress distribution and failure characteristics around the openings under different lateral pressure coefficients and inclination angles. The relationships among shape parameters, stress states, and failure modes are analyzed. The results indicate that the stress distribution is primarily governed by the shape and inclination angle of the opening, whereas the lateral pressure coefficient mainly influences the magnitude of stress concentration. Within the scope of this study, isosceles trapezoidal openings are most sensitive to the lateral pressure coefficient, followed by square and three-centered arch openings, with circular openings being the least sensitive; compressive stress concentration zones form at the endpoints of the openings or locations with abrupt curvature changes (such as the corners of squares and trapezoids, and the shoulders/corners of arches), and the compressive stress concentration is most pronounced when the opening inclination angle is approximately 45°. The minimum circumferential stress increases monotonically with the lateral pressure coefficient, transitioning from tensile to compressive and eventually stabilizing. DEM simulations further reveal that the initial failure zone corresponds closely with the stress concentration zone: tensile cracks dominate at low lateral pressure coefficients, while shear-dominated failures emerge as the coefficient increases. Among the studied shapes, circular openings show the greatest capacity to suppress tensile stress concentration, whereas trapezoidal openings are the most unfavorable in this regard.

How inter-drawbell spacing dictates three-dimensional flow interactions and the formation of stagnant pillars under uneven drawdown remains a critical, unquantified challenge in block caving. To resolve this scientific problem, a multi-scale kinematic framework was established. Large-scale (1:33) physical drawing tests were conducted and utilized to rigorously calibrate a Discrete Element Method (DEM) model, analyzing granular flow dynamics across varying drawbell spacings (4, 6, and 8 m). To quantitatively decode complex spatial interactions, a novel data-driven framework based on the DBSCAN-α-shape algorithm was introduced, enabling the precise 3D morphological reconstruction of the Isolated Extraction Zone (IEZ). The integrated analysis revealed that the mass of stagnant pillars increases quadratically with spacing, governed by a determinable static equilibrium limit. Furthermore, the non-linear morphological evolution of the IEZ was strictly quantified, transitioning from an initial constrained ellipsoid to an unconfined “inverted trumpet” geometry. Based on the site-specific fragmentation profile (predominant 200–300 mm in-situ fragment size), a 6 m spacing was quantitatively identified as the optimal configuration to balance maximum flow efficiency with pillar stability. This research provides a new analytical paradigm and precise design criteria for multi-drawbell extraction.

This study explores the damage characteristics and failure behaviors of cemented tailings backfill (CTB) under cyclic impact loading via drop-hammer impact tests, NMR tests, AE-monitored uniaxial compression tests and SEM observations, combined with damage mechanics and NMR fractal theory for quantitative analysis using CTB samples with a cement-tailings ratio of 1:3 and slurry mass fraction of 76%. The results show that cyclic impact loading obviously deteriorates the macroscopic mechanical properties of CTB, with its brittleness and damage variables rising with increasing impact times; the slope of tangent modulus-strain curve declines while crack closure stress and strain increase gradually. CTB presents double peaks in T₂ spectrum dominated by micropores, whose peak T₂ values grow and NMR fractal dimension decreases as impact cycles increase. Both AE counts and energy change periodically during loading, and RA-AF parameters indicate that the failure mode shifts from tension-dominated fracture to shear-tension mixed fracture. Finally, a full-process damage constitutive model of CTB under coupled impact damage and loading is established by adopting Weibull distribution to describe the randomness of its microscopic element strength.

Regarding the limitation that the Hoek–Brown failure criterion fails to account for the anisotropy of stratified rocks—widely used in geotechnical engineering systems such as mining, tunneling, and water conservancy projects—this study employed a Gaussian function to quantitatively characterize the influence of inclination on the Hoek–Brown parameter mi, proposing a modified Hoek–Brown failure criterion for stratified rocks that is simple in form with clearly defined parameters. It was then validated using triaxial compression test results from various stratified rock types including phyllite, sandstone, slate, and schist with varying inclinations and confining stresses, demonstrating high accuracy in predicting peak compressive strength with 93.6

The block caving method is a kind of mining method with high production rates and low production costs, and the key to the method hinges on the layout and design of the drawbell. Based on the Pulang Copper Mine Project, a scaled experimental apparatus incorporating the drawbell structure was proposed and designed, and a comprehensive numerical simulation and analysis scheme was developed. Indoor tests and numerical simulations of the caved rock release model were designed under different drawbell crossing angle (/1) values (90 degrees, 80 degrees, 75 degrees), and the effects of these different/1 values on the morphology and characteristic parameters of the extraction zone were systematically quantified under various drawing heights H (10 cm, 25 cm, 45 cm, 65 cm, 80 cm). At the same time, an intelligent extraction model based on DBSCAN-alpha shape was developed to achieve intelligent extraction and volume calculation of the extraction zone. It was found that the morphology of the extraction zone exhibited an ellipsoid-like shape at different /1-values. The discharge rate Q, ellipsoid characteristic parameters a and b, flow rate, and release volume all increased with the increase of drawing height H, and the growth rate of these parameters accelerated with the increase of the /1 value. Notable results have been achieved in the study of ore release from single drawbell.

Long-hole raise blasting (LHRB) is a highly efficient excavation method that is used extensively in underground mining and civil engineering. However, deviations in drilling are usually not accounted for in LHRB, which may adversely affect the efficiency and progress of raise excavation. In this paper, the effect of drilling deviation on the optimization of LHRB is investigated. The actual trajectories of the blastholes were measured, and the deviation rates between different diameters were compared. The effects of the drilling deviation on the burn-cut blasting mode (BCBM) and spherical cartridge blasting mode (SCBM) of LHRB were theoretically analyzed. Numerical models with vertical holes that consider the actual hole location at different positions of the raise were subsequently developed to simulate the raise blasting damage. The results indicated that the BCBM relied substantially on the drilling accuracy to provide free surface and compensation space for further blasting, whereas the requirements of drilling deviation for the SCBM were less strict. With increasing hole deviation in the BCBM, the height of the failure area of the raise blasting increased. Optimization designs that combine the BCBM and SCBM were proposed to strike a balance between the efficiency and reliability of LHRB. A 40 m high slot raise in a large-diameter long-hole (LDL) stope was successfully formed by multimode LHRB. The field test results reveal that the optimization of LHRB is feasible in practical engineering.

In deep-buried tunnel construction, the instability issues caused by excavation under high-stress conditions have been challenging. In this study, a series of true triaxial single-sided unloading tests were performed on jointed sandstone specimens with different joint inclinations to explore the fracture behavior of jointed rock at different burial depths under excavation unloading. The results show that the specimen under Loading Path I (unloading first and then loading) exhibits an unloading rebound phenomenon and a distinct yielding stage, reflecting a ductile failure. The specimen under Loading Path II (loading first and then unloading) shows a higher brittleness and greater susceptibility to failure, without an obvious yield stage. In the specimen under Loading Path I, the macroscopic failure forms a V-shaped notch due to buckling tensile cracks, whereas the failure of specimen under Loading Path II resembles the rockburst phenomenon with far-field tensile cracks. Additionally, the increased burial depth increases the yield and peak stresses of specimen and suppresses large-scale cracks but intensifies the crack propagation in specimen upon unloading, resulting in a more severe failure. The joint inclination affects the crack propagation and fragmentation characteristics of specimen, with the greatest influence occurring at 30°–45°. At joint inclinations of 0°–30°, the failure of specimen is dominated by shear cracks initiated from joint tips. At joint inclinations of 45°–60°, the failure of specimen involves mixed tensile-shear cracks, while at the joint inclination of 90°, the tensile cracks parallel to the joint dominate.

To investigate the effects of different moisture conditions and numbers of freeze–thaw cycles on the damage deterioration behavior of red sandstone, three freeze–thaw conditions were used in this study: GA (sealed water-retaining state after saturation), GB (semi-immersed state after saturation), and GC (full immersion state after saturation). The samples were subjected to 20, 40, and 60 freeze–thaw cycles, followed by uniaxial compression tests and acoustic emission (AE) monitoring. By analysing the stress–strain curves, tangent modulus–strain curves, crack-closure parameters, brittleness indices, AE counts, and energy dissipation characteristics, the freeze–thaw damage mechanism of red sandstone samples under disparate moisture boundary conditions was revealed. The results show that as the number of freeze–thaw cycles increases, the uniaxial compressive strength and tangential deformation modulus of red sandstone samples gradually decrease, whereas the peak strain and full compaction strain increase. The crack-closure stage is prolonged, and the failure process changes from sudden brittle failure to progressive damage failure. The degree of damage differed among the samples under different moisture conditions; overall, the GB group (semi-immersed state) exhibited the most pronounced deterioration, followed by the GC group (fully immersed state), whereas the GA group (sealed water-retaining state) experienced relatively weak deterioration. Energy analysis indicates that freeze–thaw cycling decreases the elastic energy storage capacity and increases the proportion of dissipated energy. The freeze–thaw damage variable established on the basis of the peak dissipated energy ratio can be used to characterize the strength attenuation and deformation growth processes effectively.

The stability of cemented tailings backfill (CTB) is critical for the safe operation of underground mines. Inevitably, operational constraints introduce two types of layered interfaces within CTB: transition heterogeneous structural interface (THSI) and continuous homogeneous structural interface (CHSI), thereby transforming CTB into layered cemented tailings backfill (LCTB). In this study, three-dimensional physical models were developed to simulate rock-backfill systems in underground mines. Five blasting tests were conducted to investigate the effects of charge position and LCTB strength configuration. The analyses focused on dynamic volumetric strain responses (Δk, defined as the attenuation ratio of the first peak volumetric strain εv(max) at identical distances), pre- and post-blast sonic velocity change rates (η, used to quantify damage severity), as well as damage morphology and failure evolution.The results indicate that the dynamic failure of the rock-backfill system proceeds through three sequential stages: crack initiation and backfill extrusion, crack propagation and blasting gas invasion, and rock-backfill system destruction. For LCTB containing a THSI, placing the charge within the high-strength LCTB layer accelerates the attenuation of εv(max), reflected by an increase in Δk (from 0.71 to 2.32), while the damage index η (from < 13% to < 8%) decreases progressively. Conversely, for LCTB containing a CHSI, aligning the charge with the CHSI elevation results in more convergent εv(max) attenuation behavior, with Δk decreasing from 2.54 to 1.32, accompanied by reduced damage levels (η < 10%). These results suggest that, under the investigated model conditions, positioning the charge within the high-strength layer in the presence of a THSI, or aligning the charge with the CHSI, is favorable for mitigating LCTB degradation. The findings provide a mechanistic basis for understanding charge-layered interface interactions in two-step stope blasting and offer engineering-relevant insight into charge placement in layered cemented backfill systems.

To investigate the influence of such disturbances on Mode III fracture behavior, ENDB specimens with varying degrees of impact-induced damage were prepared and tested. The results indicate that both increasing impact cycles and higher air pressure promote the initiation and linkage of internal microdefects, resulting in cumulative and irreversible damage. Compared with intact specimens, the Mode III fracture toughness (KIII) decreases by 15.2%, 22.2%, 40.4%, and 53.1% after 1 to 4 impact cycles, respectively. A similar reduction trend is observed as the impact pressure increases. In addition, prior impact damage significantly affects crack propagation behavior. The average crack growth velocity declines continuously with increasing impact cycle. After a single impact, the propagation speed drops from 193.62 m/s to 85.47 m/s, corresponding to a reduction of 56%, while a total decrease of 91.8% is observed after four impacts. A pronounced reduction in crack velocity is also observed with increasing impact pressure, with a decrease of 92.4% as pressure rises from 0.35 MPa to 0.45 MPa. Fracture surface analysis further reveals that both higher impact cycle and pressure lead to a broader distribution of surface height variations and a noticeable increase in fractal dimension. These changes indicate a progressive enhancement in fracture surface roughness under stronger dynamic disturbance conditions.

Muddy siltstone combines the characteristics of both sandstone and mudstone, and is prone to instability over time. To study the long-term stability of tunnel engineering in this stratum, this article taking the cross-river metro tunnel section as the engineering background, and conducting research on the stress and deformation of the tunnel surrounding rock. Firstly, uniaxial compression creep tests were conducted on muddy siltstone to study the creep deformation law under graded loading. Secondly, a nonlinear damage creep model was established based on the Burgers model, and the experimental results were fitted. Finally, the proposed creep model was applied to the COMSOL Multiphysics numerical simulation software to perform multi field coupled calculations on the operation of metro tunnels. The research results show that: (1) Muddy siltstone undergoes the entire process of decaying creep, steady creep and accelerated creep. (2) The proposed nonlinear damage creep model can accurately describe the creep characteristics of muddy siltstone, especially in the accelerated creep stage. (3) Applying nonlinear damage creep model to tunnel numerical simulation calculation, it was found that the most obvious part of tunnel rock creep deformation is the tunnel arch crown. By comparing with on-site monitoring data, indicated that the established creep-fluid-structure coupling tunnel model can be used to predict surrounding rock deformation. The creep-fluid-structure coupling tunnel model proposed in this study provides a new perspective for the design and safety assessment of cross river tunnels in soft rock formations, which helps to achieve more accurate long-term stability prediction.

Empirical observations have revealed the dynamic evolution of slope stability with landslide displacement, yet existing methods lack a rigorous mechanical framework to characterize this time-dependent process. To address the theoretical limitations of conventional early warning systems that depend on kinematic parameters (e.g., velocity and acceleration), this study develops a multiscale modeling framework integrating damage mechanics and renormalization group theory. We propose a shear constitutive model incorporating progressive rock damage and establish critical state criteria through renormalization group theory, deriving a displacementcoupled dynamic safety factor equation. Validation via field data from a slope engineering project and the finite difference method (FDM) simulations demonstrates two critical advancements: (1) The non-uniformity of overburden normal stress across the slip surface leads to spatially varying shear constitutive curves in different regions; (2) Slope stability displays nonlinear evolutionary phases (elastic-plastic transition -* accelerated degradation -* residual state) directly linked to displacement progression. This framework pioneers a physicsbased mapping between displacement monitoring and slope stability states, establishing mechanistic foundations for intelligent early landslide warning systems.

Rock mass engineering serves as a critical foundation for infrastructure construction and resource development [...]

Understanding soil properties’ spatial and temporal variability is essential for optimizing road construction and maintenance practices. This study investigates the seasonal variability of soil properties along a 4.8 km roadway in Maiduguri, Nigeria. Using a novel integration of network analysis and geotechnical testing, we analyzed nine soil parameters (e.g., particle size distribution (PSD), Atterberg limits, California bearing ratio) across wet (September 2024) and dry (January 2021) seasons from 25 test stations. Average Atterberg limits (LL: 22.8% wet vs. 17.5% dry; PL: 18.7% wet vs. 14.7% dry; PI: 4.2% wet vs. 2.8% dry; LS: 1.8% wet vs. 2.3% dry), average compaction characteristics (MDD: 1.8 Mg/m3 wet vs. 2.1 Mg/m3 dry; OMC: 12.3% wet vs. 10% dry), and average CBR (18.9% wet vs. 27.5% dry) were obtained. Network construction employed z-score standardization and similarity metrics, with multi-threshold analysis (θ = 0.05, 0.10, 0.15) revealing critical structural differences. During the wet season, soil networks exhibited a 5.0% reduction in edges (321 to 305) and density decline (1.07 to 1.02) as thresholds tightened, contrasting with dry-season networks retaining 99.38% connectivity (324 to 322 edges) and stable density (0.99). Seasonal shifts in soil classification (A-4(1)/ML wet vs. A-2(1)/SM dry) underscored moisture-driven plasticity changes. The findings highlight critical implications for adaptive road design, emphasizing moisture-resistant materials in wet seasons and optimized compaction in dry periods.

In this experimental investigation, SHPB impact tests were conducted on short core-in-compression (SCC) samples with varying crack spacings to investigate the relationships between peak fracture load and rock mode II fracture toughness at different crack spacings, as well as the evolution of failure morphology. Additionally, discrete element simulations using PFC3D were performed to investigate the fracture progression, crack development, and energy variations from a microscale perspective. Experimental observations demonstrate enhanced mode II dynamic fracture toughness corresponding to larger crack spacing configurations, and intercrack distance variations exert a dominant control on the fracture propagation patterns observed in the tested samples. Furthermore, with increasing fracture spacing, quantitative analysis reveals a gradual reduction in shear crack prevalence within samples, paralleled by a commensurate increase in tensile crack formation rates. The energy consumed by a sample during crack propagation progressively increases as the crack spacing increases, a trend that is influenced by both the crack length and the number of microcracks. The failure modes of the samples with C/H values of 0.4 and 0.5 change, suggesting the existence of a critical C/H value between 0.3 and 0.4, which causes the SCC samples to transition from mode II fracture behaviour.

High-plasticity clay soils pose significant challenges in geotechnical engineering due to their poor mechanical properties, such as low strength and high compressibility. Lime–cement stabilization offers a sustainable solution, but optimizing additive proportions requires advanced analytical approaches to decipher complex soil-stabilizer interactions. This study investigates the stabilization of high-plasticity clay soil (CH) sourced from Kano, Nigeria, using lime (0–30%) and cement (0–8%) for thirty (30) sample combinations to optimize consolidation and strength properties. Geotechnical laboratory tests (consolidation and UCS) were evaluated per ASTM standards. Multivariate analysis integrated principal component analysis (PCA) with regression modeling (PCR) for sensitivity and causality assessment. Optimal stabilization (15% lime + 6% cement) significantly improved soil properties: void ratio reduced by 58% (0.60→0.25), porosity by 49.5% (0.38→0.19), UCS increased by 222.5% to 2670 kPa (28 days), preconsolidation stress by 206% (355.63→1088.92 kPa), and compressibility modulus by 16% (7048→10,474.28 kPa). PCR sensitivity analysis attributed 46% of UCS variance to PC1 (compressibility parameters: void ratio, porosity, compression index; β = 0.72). PCR Causality analysis shows improvment with curing (R2: 68.7% at 7 days→83.0% at 28 days; RMSE: 11.2→7.8 kPa). PCR establishes compressibility reduction as the dominant causal mechanism for strength gain, providing a robust framework for dosage optimization beyond empirical approaches.

The morphology of the rock-fill interface, formed during mining and filling operations in underground mines, is directly related to the destabilization and damage of the cemented backfill under dynamic blasting loads. Previous studies often simplify the rock-fill interface to a planar shape; however, exploration results of empty areas in the quarry often characterize the rock-fill interface with jagged undulations. Applying continuum mechanics and numerical simulation software based on the finite difference method, three models of cemented backfill with different morphologies of serrated rock-fill interfaces were established as the experimental group, and one model with a flat and straight rock-fill interface was established as the control group; The time-history curve of the explosive load on the walls of equivalent cavities after rock blasting was derived and incorporated into a numerical model to simulate the two-step perimeter hole blasting in quarries. The dynamic damage response of cemented backfill under blasting loads was investigated by combining it with the backfill's damage criteria, and the influences of factors such as sawtooth width (SW) at the rock-fill interface, cement-sand ratio (CSR), side hole distance (SHD), vertical stress (σh), and others on the damage extent and mode were determined. The results show that: The damage area of the cemented backfill at a planar rock-fill interface resembles a rectangle, whereas at a jagged rock-fill interface with larger sawtooth widths, the damage area tends to approximate a rhombus, making it more prone to wedge-shaped damage; When vertical stress (σh) is similar, between two adjacent cemented backfill layers with differing CSR, the layer with the higher CSR exhibits slower attenuation of the peak vibration velocity at each mass point, resulting in a larger damage area and an increased likelihood of interlayer misalignment due to inconsistent vibration velocities; With the CSR constant, a larger σh results in a smaller damage area; Furthermore, the damage area of the cemented backfill is inversely correlated with SHD, and in engineering practice, selecting a reasonable SHD is crucial to maintaining the stability of the cemented backfill when the quantity of explosives for side holes cannot be reduced.

Hybrid composite pile foundations face critical challenges in terms of optimizing load transfer mechanisms across variable soil densities, particularly in regions like Kano, Nigeria, characterized by loose to dense sandy deposits and fluctuating groundwater levels. This study addresses the need for sustainable, high-performance foundation systems that are adaptable to diverse geotechnical conditions. The research evaluates the mechanical behavior of steel–concrete and timber–concrete hybrid piles, quantifying skin friction dynamics, combining eight (8) classical ultimate bearing capacity (UBC) methods (Vesic, Hansen, Coyle and Castello, etc.) with numerical simulations, and assessing load distribution across sand relative densities (10%, 35%, 50%, 75%, 95%). Laboratory investigations included the geotechnical characterization of Wudil River well-graded sand (SW), direct shear tests, and interface shear tests on composite materials. Relative densities were calibrated using electro-pneumatic compaction. Increasing Dr from 10% to 95% reduced void ratios (0.886–0.476) and permeability (0.01–0.0001 cm/s) while elevating dry unit weight (14.1–18.0 kN/m3). Skin friction angles rose from 12.8° (steel–concrete) to 37.4° (timber–concrete) at Dr = 95%, with timber interfaces outperforming steel by 7.4° at Dr = 10%. UBC for steel–concrete piles spanned from 353.1 kN (Vesic, Dr = 10%) to 14,379 kN (Vesic, Dr = 95%), while timber–concrete systems achieved 9537.5 kN (Hansen, Dr = 95%). PLAXIS simulations aligned closely with Vesic’s predictions (14,202 vs. 14,379 kN). The study underscores the significance of soil density, material interfaces, and method selection in foundation design.

The stabilization of expansive soils is crucial for the construction projects to mitigate swelling, shrinkage, and bearing capacity issues. This study investigates the synergistic effects of cement and clinoptilolite zeolite on stabilizing high-plasticity clay (CH) soil from Kano State, Nigeria. A total of 30 admixture combinations-cement (0-8%) and zeolite (0-15%)-were tested via standardized laboratory methods to evaluate their free swell index (FSI), swell percentage, swell pressure, shrinkage, and California Bearing Ratio (CBR). Principal component (Lasso) "least absolute shrinkage and selection operator" regression modeled interactions between admixtures and soil properties. The key results include the following: (1) 6% cement + 12% zeolite reduced the FSI by 60% (45 → 18); (2) 8% cement + 15% zeolite decreased the swell percentage by 47.8% (22.5% → 11.75%); (3) 6% cement + 12% zeolite lowered swell pressure by 54.2% (240 kPa → 110 kPa); (4) 8% cement + 12% zeolite reduced shrinkage by 50% (5.6% → 2.8%); and (5) 6% cement + 9% zeolite achieved an unsoaked CBR of 80.01% and soaked CBR of 72.79% (resilience ratio: 0.8010). PCLR models explained 93.5% (unsoaked) and 75.0% (soaked) of the CBR variance, highlighting how zeolite's mediation analysis indicates that zeolite improves the bearing capacity mainly by reducing the free swell index (path coefficient = -0.91429, p < 0.0001), while conditional process modeling provided greater explanatory power (R2 = 0.745) compared to moderation-only analysis (R2 = 0.618). This study demonstrates that zeolite-cement blends optimize strength and resilience in expansive soils, with implications for sustainable infrastructure in arid and semi-arid regions.

Landslide displacement dynamically drives the evolution of slope stability, a critical phenomenon empirically demonstrated by numerous early-warning cases. Yet, conventional slope stability calculation methods fundamentally fail to capture this displacement-dependent behavior. Knowing the effect of landslide displacement on slope stability can greatly improve the efficiency of landslide warning and reduce the loss caused by landslide disaster. For this reason, this paper constructs a rock shear constitutive model based on damage mechanics. Considering the parameter differences between small-size specimens and large rock masses due to the size effect, the Hoek-Brown criterion is introduced. By the Hoek-Brown criterion, the rock shear constitutive model was successfully transformed into a slide mass shear constitutive model. Finally, the slide mass shear constitutive model was brought into the slope model and an expression for the dynamic calculation of slope safety factor based on landslide displacement was derived. In addition, Finite Difference Method (FDM) was used to verify the validity of the dynamic calculation expression of slope safety factor in this paper. The results show that each rock interface on the slip surface of the slope owns a different shear constitutive curve due to the different normal loads. The factor of safety of the slope will show a nonlinear variation with the increase of the landslide displacement.