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To efficiently realize backfilling mining with medium-deep hole caving in a gold mine, the rational determination of stope dimensions is essential. The Vlazov plate theory was employed to analyze the stress state and investigate the relationship between roof thickness and maximum tensile stress under varying stope spans. Since the latter serves as a criterion for evaluating roof strength failure, it is imperative to establish the appropriate range of parameters that ensure the rock mechanics stability during mining operations. Through central composite testing, numerical simulations were conducted to obtain mechanical response characteristics under different stope dimensions. Simultaneously, roof stress distributions and stope stability were analyzed. A second-order response surface model was constructed based on these findings, enabling the formulation of a comprehensive optimization framework. The interaction between variables within this framework was carefully considered when defining the objective functions for optimization. By integrating chaotic mapping into genetic algorithms, a multi-objective optimization approach was implemented, yielding 17 Pareto-optimal solutions. Ultimately, the optimized stope geometry was determined to have a chamber span of 31.89 m, a pillar span of 29.14 m, and a roof thickness of 5.35 m. This configuration represents the optimal balance between mechanical performance and mining efficiency in the context of medium-deep hole caving operations within the gold mine.

A novel true triaxial apparatus (TTA) has been designed and fabricated to investigate the mechanical behavior of deep underground engineering under high-stress conditions and low-frequency disturbance loads. This apparatus features a two-rigid, one-flexible loading system, with rigid loading applied along the directions of the maximum and intermediate principal stresses, offering maximum load capacities of 2000 kN and 4000 kN, respectively. The direction of the maximum principal stress is also equipped with dynamic loading capabilities, enabling low-frequency disturbance loads with frequencies up to 20 Hz and amplitudes of 0.5 mm. The minimum principal stress direction utilizes flexible loading, with pressure capabilities of up to 120 MPa. Moreover, the integration of a high-rigidity loading frame and high-precision servo control systems has significantly enhanced the apparatus’s performance and data accuracy, particularly in small-scale deformation tests. Additionally, a dual-actuator, dual-loop servo control mode is employed to effectively suppress eccentric loading effects in true triaxial tests. To validate the reliability of the TTA and to preliminarily explore the effects of stress paths and disturbances on deep rock mechanical properties, true triaxial tests were conducted using granite. The results demonstrate that both the intermediate principal stress and disturbance frequency significantly influence the strength and failure modes of the rock. Static and disturbance tests exhibited excellent high repeatability and consistency, further confirming the accuracy and reliability of the apparatus. Overall, the TTA provides a novel methodology for investigating the mechanical properties of deep rock masses under high-stress and low-frequency disturbance conditions, making it an effective tool for addressing related scientific and engineering challenges.

Using a tessellation method in Neper, the simplified 3DEC‐GBM (three‐dimensional discrete element grain–based model) is proposed for generating joint models with different roughnesses. The model is extended by implementing the generalized effective stress law to mimic the shear behavior of unsaturated sandstone. The grain‐scale mechanical parameters of the model were calibrated to correspond to the mechanical behavior of sandstone samples measured in the laboratories. The simulations accurately explain complex macroscopic shear behavior in terms of the mesoscale interaction of grains. The modeling results show that water has a deteriorating effect that weakens the strength of the joint, and the degree of reduction in joint strength rises with increasing saturation. Increasing normal stress and roughness can all improve the shear strength of the joint. We conclude that the proposed model is a convenient approach to analyze the shear response of unsaturated sandstone at varying roughness and normal stress.

Precise forecasting of rockburst intensity categories is vital to safeguarding operational safety and refining design protocols in deep underground engineering. This study proposes an intelligent forecasting framework through the integration of k-medoids-SMOTE and the BSLO-optimized Random Forest (BSLO-RF) algorithm. A curated dataset encompassing 351 rockburst instances, stratified into four intensity grades, was compiled via systematic literature synthesis. To mitigate data imbalance and outlier interference, z-score normalization and k-medoids-SMOTE oversampling were implemented, with t-SNE visualization confirming improved inter-class distinguishability. Notably, the BSLO algorithm was utilized for hyperparameter tuning of the Random Forest model, thereby strengthening its global search and local refinement capabilities. Comparative analyses revealed that the optimized BSLO-RF framework outperformed conventional machine learning methods (e.g., BSLO-SVM, BSLO-BP), achieving an average prediction accuracy of 89.16% on the balanced dataset—accompanied by a recall of 87.5% and F1-score of 0.88. It exhibited superior performance in predicting extreme grades: 93.3% accuracy for Level I (no rockburst) and 87.9% for Level IV (severe rockburst), exceeding BSLO-SVM (75.8% for Level IV) and BSLO-BP (72.7% for Level IV). Field validation via the Zhongnanshan Tunnel project further corroborated its reliability, yielding an 80% prediction accuracy (four out of five cases correctly classified) and verifying its adaptability to complex geological settings. This research introduces a robust intelligent classification approach for rockburst intensity, offering actionable insights for risk assessment and mitigation in deep mining and tunneling initiatives.

In order to explore the influence of dynamic disturbance on creep behavior of rock, the creep damage evolution in rock under the dynamic disturbance are reproduced with creep damage model. In this model, the constitutive law of rock under combined creep and dynamic loading condition is implemented based on elastic damage principle and Norton-Bailey equation in COMSOL Multiphysics. The numerical results show that the dynamic disturbance alters the creep behavior of rock in three aspects, i.e., time, space and energy. In temporal aspect, dynamic disturbance not only accelerates the creep damage evolution of rock, but also leads to the tensile damage accounting for the main damage mode. The tensile damage mode mainly occurs during the unloading stage of dynamic disturbance, and the tendency of transition becomes evident under more dynamic disturbances. In spatial aspect, the dynamic disturbance may facilitate the development of rock damage, resulting in unstable rock failure. In energy aspect, the dynamic disturbance causes creeping rock to absorb and release energy in a short time, which can be quantified with the energy dissipation rate. The residual deformation caused by the dynamic disturbance is also exponentially related to the energy dissipation rate.

The stabilization of rock mass vibrations in underground excavations presents a critical engineering challenge due to the interplay of viscoelastic dynamics, impulsive shocks from blasting or rock bursts, and time-varying delays induced by wave propagation and sensor–actuator networks. In this paper, an integral sliding mode control scheme is developed for a Kelvin–Voigt type hyperbolic system subject to such impulsive effects and time-varying delays. To preserve sliding surface continuity under impulsive disturbances, the impulse information is explicitly incorporated into the design of the integral sliding function. The resulting sliding mode dynamics, which include discrete state jumps, are analyzed using a piecewise Lyapunov functional combined with inequality techniques; sufficient conditions are derived to guarantee asymptotic stability. Moreover, a sliding mode control law is synthesized to ensure that the system trajectories reach and remain on the sliding manifold from the initial time onward, despite parameter uncertainties and external disturbances. Numerical simulations with parameters reflecting realistic mining scenarios verify the effectiveness of the proposed control strategy, demonstrating its potential for practical rock mass vibration stabilization in geotechnical engineering.

There are few studies on the management methods of large-scale goaf groups per the specific surrounding rock mass conditions of each goaf. This paper evaluates comprehensively the stability of the multistage large-scale goaf group in a Pb-Zn mine in Inner Mongolia, China, via the modified Mathews stability diagram technique. The volume of each goaf to be backfilled was quantitatively analyzed in the combination of theoretical analysis and three-dimensional laser scanning technology. The corresponding mechanical characteristics of the filling were determined by laboratory testing while formulating the treatment scheme of the large goaf group using the backfill method. The applicability of the treatment scheme using the backfill was verified by the combination of the numerical results of the distribution of the surrounding rock failure zone and the monitored data of the surface subsidence. The research results and treatment scheme using the backfill can provide a reference for similar conditions of mines worldwide.

In order to explore the failure characteristics and safety control measures of multiple mining soft rock roadway, and based on the fracture characteristics of mining soft rock roadway, drilling column and rock mechanics test results, FLAC3D is used to establish a numerical model to analyze the failure characteristics of the original support soft rock roadway under multiple mining, and the joint control measures of goaf filling and reinforcement support are proposed, field measurement and analysis of its treatment effect. The results show that: the failure of support is obvious, the vertical stress of mining face is transferred to the surrounding rock mass, and the stress concentration and deformation of the lower right side roadway are caused The filling of the goaf limits the stress concentration, displacement and plastic range of the surrounding rock to a certain extent, and the reinforcement support further strengthens the strength of the broken surrounding rock. The comprehensive treatment scheme of goaf filling and secondary reinforcement support has achieved good engineering results.

The creep behavior of deep weak rock masses is important due to an underground opening. Appreciating the nature and source of these deformations requires the knowledge of rock mass and ground support interaction. The theoretical solution of the backfill’s internal stresses needs to consider the time-dependent effect. In the present study, the coupling interaction between the creep behavior of the nearby rock material and the internal stresses in the backfilled stope is considered and the interaction characteristics are given analytically. A solution is then proposed regarding the time-dependent stress distribution in suborbicular backfilled stope interaction with creeping rock. Besides, the correctness of the theoretical solution is verified by numerical simulation, while influential parameters such as stope buried depth, lateral pressure coefficient, horizontal stress ratio, creep time of surrounding rock mass, delay time of the backfill, and Young’s modulus are thoroughly discussed. Research shows that when the stope buried depth becomes large as well as the rheological effect of the nearby rock materials becomes significant, the stress distribution in the backfill material exceeds its self-weight stress and presents significant time-dependent characteristics. The delayed backfilling weakens the backfill’s ground support effect on the nearby rock material. Hence, timely and multipoint simultaneous backfilling is needed for a stope with significant rheological deformation of surrounding rock mass. Lastly, this work will offer useful knowledge while designing the backfill materials for underground mines.

This study investigates the stability of deep granite roadways under cyclic loading and unloading, focusing on the energy evolution of surrounding rock in the Sanshandao Gold Mine. In-situ stress measurements between - 835 m and - 1140 m reveal a horizontally dominated tectonic stress field, with both maximum and minimum horizontal stresses increasing approximately linearly with depth. On this basis, true triaxial cyclic loading-unloading tests were carried out on granite specimens to simulate burial depths of 500-2000 m. The results show that irreversible principal strains in the σ₁ and σ₃ directions increase approximately exponentially with cycle number, whereas the σ direction exhibits an almost linear trend. With repeated cycling, axial elastic energy continues to accumulate while circumferential dissipated energy grows and then stabilises, indicating a damage-induced energy conversion mechanism in which a large part of the input energy is consumed by plastic deformation, frictional sliding and crack development rather than being released catastrophically. Using these insights, an energy-based support design framework was developed and applied to the - 1050 m haulage roadway at Sanshandao, where an optimised split-set support system with enhanced energy-absorption capacity significantly improved roadway stability. The proposed energy dissipation framework and associated support strategy provide a practical basis for mitigating dynamic hazards in deep hard-rock mining.