Search Results (116)

To support intelligent and sustainable mine engineering, this geotechnics-based study integrates laboratory testing, three-dimensional numerical simulation, and field monitoring to optimize roadway support and improve resource efficiency. This study investigates the geotechnical behavior of the surrounding rock in coalmine roadways under single-face unloading conditions, aiming to provide theoretical and practical support for surrounding rock control in underground coal mining. Excavation of the roadway creates a free surface, leading to unloading, which makes timely support crucial for preventing instability. True-triaxial single-face unloading tests and mechanical tests on hole-containing coal specimens show that the coal exhibits four characteristic stages, namely fissure compaction (closure), elastic deformation, yielding, and residual strength. Under a confining stress of 4 MPa, the peak strength of Coal Seam No. 3 in the true-triaxial single-face unloading test reached 32.4 MPa, whereas the peak strength of the hole-containing coal specimen was only 17.1 MPa, and failure occurred as instantaneous global instability with an “X”-shaped conjugate shear pattern. Numerical simulations were conducted to optimize the roadway’s surrounding rock control scheme, indicating that increasing the bolt length increases the proportion of the load carried by the rock bolts while reducing the load borne by the cable bolts. In addition, advance abutment pressure increases the forces in the support system and amplifies deformation of the solid rib, coal-pillar rib, and roof; roadway surface convergence is dominated by floor heave. Full article

Roadways driven along the floor of thick coal seams, while retaining the top coal, form “thick coal seam floor roadways.” These large-section roadways feature a composite coal-rock roof and weak coal ribs, leading to low overall strength and poor stability of the surrounding rock. Significant deformation and “necking” often occur, accompanied by roof falls and rib spalling, which are exacerbated under high stress or adverse geology, threatening mine safety and production. In this study, the 2201 haulage gateway in Yingpanhao Coal Mine is investigated to address surrounding rock control in such deep roadways. Using field investigation, theoretical analysis, numerical simulation, and similar simulation tests, the failure mechanisms of ribs and roofs are analyzed. Rib failure is characterized by tensile fracture in the shallow zone, splitting failure in the medium-depth zone, and incomplete conjugate shear in the deep zone. Corresponding mechanical models are established, and a method for calculating total rib failure depth—combining tensile/splitting and shear failure depths—is proposed, along with a bolt length design formula. Based on this, a synergistic roof-and-rib support technology is developed. The failure mechanism and optimal support scheme are validated through simulation tests and successfully applied in the field, demonstrating satisfactory performance. The findings provide a valuable reference for support design in similar mining roadways. Full article

With the depletion of shallow coal resources, deep extra-thick coal seam mining has become vital for energy security, yet fully mechanized top-coal caving (FMTC) goaf-side roadways face severe challenges of excessive advanced deformation and intense strata behavior. To address this gap, this study took the 4301 tailgate of a coal mine in Shaanxi province as the engineering background, integrating field investigation, theoretical analysis, FLAC^3D numerical simulation, and industrial tests. Guided by the key stratum theory, we systematically analyzed the influence of overlying key strata fracture on strata pressure. The results show three key strata: near-field secondary key strata (KS1, KS2) with “vertical O-X” fracturing and far-field main key stratum (MKS) with “horizontal O-X” fracturing. The radial extrusion force from MKS rotational blocks is the core cause of 200 m range advanced deformation. A collaborative control scheme of near-field key strata directional fracturing roof-cutting pressure relief and high-strength bolt-cable support was proposed. Industrial verification indicates roadway deformation was significantly reduced, with roof subsidence, floor heave, and rib convergence controlled within safe engineering limits. This study fills the gap of insufficient research on far-field key strata’s impact, providing a reliable technical solution for similar extra-thick coal seam FMTC goaf-side roadway surrounding rock control. Full article

Maintaining the stability of the mine roadway is of paramount importance, as it is critical in ensuring the daily operational continuity, personnel safety, long-term economic viability, and sustainability of the entire mining operation. Significant instability can trigger serious disruptions—such as production stoppages, equipment damage, and severe safety incidents—which ultimately compromise the project’s financial returns and future prospects. Therefore, the proactive assessment and rigorous control of roadway stability constitute a foundational element of successful and sustainable resource extraction. In China, thick and extra-thick coal seams constitute over 44% of the total recoverable coal reserves. Consequently, their safe and efficient extraction is considered vital in guaranteeing energy security and enhancing the efficiency of resource utilization. The surrounding rock of gob-side roadways in typical coal seams is often fractured due to high ground stress, intensive mining disturbances, and overhanging goaf roofs. Consequently, asymmetric failure patterns such as bolt failure, steel belt tearing, anchor cable fracture, and shoulder corner convergence are common in these entries, which pose a serious threat to mine safety and sustainable mining operations. This deformation and failure process is associated with several parameters, including the coal seam thickness, mining technology, and surrounding rock properties, and can lead to engineering hazards such as roof subsidence, rib spalling, and floor heave. This study proposes countermeasures against asymmetric deformation affecting gob-side entries under intensive mining pressure during the fully mechanized caving of extra-thick coal seams. This research selects the 8110 working face of a representative coal mine as the case study. Through integrated field investigation and engineering analysis, the principal factors governing entry stability are identified, and effective control strategies are subsequently proposed. An elastic foundation beam model is developed, and the corresponding deflection differential equation is formulated. The deflection and stress distributions of the immediate roof beam are thereby determined. A systematic analysis of the asymmetric deformation mechanism and its principal influencing factors is conducted using the control variable method. A support approach employing a mechanical constant-resistance single prop (MCRSP) has been developed and validated through practical application. The findings demonstrate that the frequently observed asymmetric deformation in gob-side entries is primarily induced by the combined effect of the working face’s front abutment pressure and the lateral pressure originating from the neighboring goaf area. It is found that parameters including the immediate roof thickness, roadway span, and its peak stress have a significant influence on entry convergence. Under both primary and secondary mining conditions, the maximum subsidence shows an inverse relationship with the immediate roof thickness, while exhibiting a positive correlation with both the roadway span and the peak stress. Based on the theoretical analysis, an advanced support scheme, which centers on the application of an MCRSP, is designed. Field monitoring data confirm that the peak roof subsidence and two-side closure are successfully limited to 663 mm and 428 mm, respectively. This support method leads to a notable reduction in roof separation and surrounding rock deformation, thereby establishing a theoretical and technical foundation for the green and safe mining of deep extra-thick coal seams. Full article

This paper concerns the issue of selecting appropriate stress field parameters for predicting the stability of headings driven under the geological and mining conditions of Polish underground copper mines. The problem is of key importance due to strict safety requirements in mine workings that serve ventilation and transport functions. Numerical analyses were carried out for four stress field variants: the stress state determined based on Bulin’s formulas (variant 1), the hydrostatic stress state (variant 2), and stress states determined from in situ measurements conducted in the Rudna mine (variant 3 and variant 4). Numerical simulations were performed for a group of four headings, supported with fully grouted rock bolts, in the geological and mining conditions of the Rudna mine. Stability assessment was performed using the finite element method (FEM). Rock mass input parameters for the modeling were obtained with RocLab 1.0, applying the Hoek–Brown classification, while numerical analyses employed the Mohr–Coulomb failure criterion. The elastic–plastic model with softening was used to describe the rock mass behaviour. Numerical calculations were conducted in the RS2 computer program in a triaxial stress state and in a plane strain state. The range of the yielded rock mass zone in the roof of the headings was assumed as the optimal measure of the headings stability. The obtained simulation results provided a basis for recommending suitable rock bolting systems to protect the stability of headings developed under various initial stress field conditions. Full article

To optimize the support performance of rock bolts in high-stress environments, this study employs the ANSYS (Version 2022 R2) finite element numerical simulation method to systematically investigate the influence of bolt geometrical parameters (rib spacing, rib height, and bolt diameter) on the stress state of the anchoring system. A bolt–resin–sleeve model was established to analyze Mises equivalent stress distribution and peaks under a 150 kN pull-out load. The simulation results indicate that a rib spacing of 36 mm effectively promotes the diffusion of pre-stress into deeper regions, with peak stress in the bolt rod and resin ring increasing by 34.42% and 61.64%, respectively, compared to a spacing of 12 mm. Further increase in rib spacing provides limited enhancement in peak stress. A rib height of 1.0 mm achieves optimal system performance without excessively compromising the interfacial stress level. Increasing the diameter to 22 mm raised peak stress in the bolt, sleeve, and resin by 14.19%, 30.48%, and 50.77%, respectively, compared to 18 mm, balancing load capacity and material use efficiently. The optimal parameter set (36 mm spacing, 1.0 mm height, and 22 mm diameter) was validated in a field trial in Zhongmacun Mine’s 3903 East Transportation Bottom Drainage Roadway. Monitoring recorded maximum roof subsidence of 102.9 mm, stabilizing within 25 days (daily deformation < 0.2 mm), confirming the excellent performance of the bolt support system with this parameter combination in high-stress roadways. This study provides a theoretical basis and engineering reference for the optimal design of high-performance rock bolts. Full article

To address the challenge of simulating shear failure in anchor bolts within FLAC3D, a shear failure criterion, F_s(i) ≥ F_smax(i), is proposed based on the PILE structural element. Through secondary development using the FISH programming language, a modified mechanical model of the PILE element is established and integrated into the FLAC3D-FISH framework. Comparative analyses are conducted on shear tests of bolt shafts and on anchor bolt support performance under coal–rock interface slip conditions, using both the original PILE model and the modified mechanical model. The results demonstrate that the shear load–displacement curve of the modified PILE model clearly reflects shear failure characteristics, satisfying a quantitative shear failure criterion. Upon failure, both the shear force and axial force of the structural element at the failure point drop abruptly to zero, enabling effective simulation of shear failure in anchor bolts within the FLAC3D environment. Using the modified model, the distribution of principal stress differences in the surrounding rock after roadway excavation is analyzed. Based on this, the concept of a stress-bearing ring in the surrounding rock is introduced. The reinforcing effects of bolt length, spacing, and ultimate load capacity on the stress-bearing ring in weak and fractured surrounding rock are investigated. The findings reveal that: (1) shear failure initiates in bolt shafts near the coal–rock interfaces, occurring earlier near the coal–floor interface than near the coal–roof interface; (2) the stress-bearing ring in weak and fractured surrounding rock shows a discontinuous and uneven distribution. However, with support improvements—such as increasing bolt length, reducing spacing, and enhancing failure load—the surrounding rock gradually forms a continuous stress-bearing ring with more uniform thickness and stress distribution, migrating inward toward the roadway surface. Full article

Tunnel construction in weak and fractured strata often faces risks such as tunnel face instability and large deformation of surrounding rock, which are difficult to effectively control using conventional support methods. Based on the engineering background of the No. 8# TA Tunnel in the F3 section of Georgia’s E60 Highway, this study employed ADECO-RS and developed a 3D numerical model with finite difference software to simulate full-face tunnel excavation process. The influence of advanced reinforcement measures on the stability of the surrounding rock was systematically investigated. The control effectiveness of different advanced reinforcement schemes was evaluated by comparing the displacement field, stress field, and plastic zone distribution of the surrounding rock under three conditions: no support, advanced pipe roof support, and a combination of pipe roof and glass fiber bolts. A comprehensive quantitative analysis of the synergistic effect of the combined reinforcement was also performed. The results indicated that significant extrusion deformation of the tunnel face and vault settlement occurred after excavation. The pressure arch developed within a range of 17.5 to 22 m above the tunnel vault. The surrounding rock of this tunnel was classified as type B (short-term stable). Deformation primarily occurred within one tunnel diameter ahead of the face, with the deformation rate significantly reduced after support. Advanced pipe roof support effectively restrained surrounding rock deformation, while the combination of advanced pipe roof and glass fiber bolts delivered better performance: reducing final convergence by 73.10%, pre-convergence by 82.69%, and face extrusion by 87.66%. The combined support also contracted the pressure arch boundaries from 17.5 to 22 m to 6–12.5 m, reduced the extent of major principal stress deflection, and significantly shrinks the plastic zone. Glass fiber bolts played a key role in controlling plastic zone expansion and ensuring stability. This study provides theoretical and numerical references for safe construction and advanced support design in tunnels under complex geological conditions. Full article

In order to determine appropriate anchoring parameters after enlarging the cross-section of the mining roadway, a comprehensive study was conducted to investigate the development of deformation and failure characteristics in the surrounding rock. The mechanical behavior of rock failure under high-stress conditions and the progressive evolution of deformation and failure from shallow to deep zones were thoroughly analyzed. It was proposed that the primary function of bolt support in mining roadways is to guide the surrounding rock to form a stable compressive arch or ring structure. The mechanical mechanism underlying the formation of such an arch under bolt guidance, along with the stability characteristics during this process, was investigated. The principles for determining bolt support parameters were established as follows: (a) ensuring the formation of a closed compressive ring within the anchorage zone around the roadway; (b) preventing shear failure at the roadway corners; and (c) controlling the extent of roof subsidence under gravitational loading. Design methodologies for determining rock bolt and anchor cable length and spacing were formulated and implemented in the support design of large-section mining roadways within million-ton fully mechanized mining faces. The cross-sectional dimensions of the supported roadway are 5.8 × 4.0 m. Field monitoring results indicate that, after stabilization of the surrounding rock deformation, the maximum convergence between both sides does not exceed 140 mm, the maximum roof subsidence remains below 40 mm, and the maximum roof separation is limited to within 4 mm. These findings provide strong evidence that the selected design parameters fully meet the engineering requirements for roadway support. Full article

In response to issues of long construction cycles, high pollution, and labor shortages in traditional cast in situ subway station construction, a refined 3D model of a large-segment prefabricated subway station was established using ABAQUS software 2024, with mechanical behavior throughout the construction process studied based on the Shenzhen Huaxia Station project case. The model incorporates a concrete inelastic damage constitutive model and a steel elastic–plastic model, accurately simulates key components, including dry joints of mortise–tenon grooves, prestressed reinforcement, and bolted connections, and implements a seven-phase construction sequence. Research findings indicate the following: (1) During component assembly, the roof vault settlement remains ≤3.8 mm, but backfilling significantly increases displacements (roof settlement reaches 45 mm, middle slab deflection measures 66.91 mm). (2) Longitudinal mortise–tenon joints develop stress concentrations due to stiffness disparities, with mid-column installation slots identified as vulnerable zones exhibiting maximum Von Mises stress of 32 MPa. (3) Mid-column eccentricity induces structural asymmetry, causing increased deflection in longer-span middle slabs, corbel contact stress differentials up to 6 MPa, and bolt tensile stresses exceeding 1.1 GPa. (4) The arched roof effectively transfers loads via three-hinged arch mechanisms, though spandrel horizontal displacement triggers 5 cm rebound in diaphragm wall displacement. Conclusions confirm overall the stability of the prefabricated structure while recommending the optimization of member stiffness matching, avoidance of asymmetric designs, and localized reinforcement for mortise–tenon edges and mid-column joints. Results provide valuable references for analogous projects. Full article

The layered composite roof of a coal mine roadway exhibits heterogeneity, with pronounced variations in layer thickness and strength. Fully grouted rock bolts installed in such layered roofs usually penetrate two or more strata and bond with them to form an integrated anchorage system. Roof failure typically initiates in the shallow strata and progressively propagates to deeper layers; thus, the mechanical properties of the rock at the free surface critically influence the overall stability of the layered roof and the load-transfer behavior of the bolts. In this study, a layered rock mass model was developed using three-dimensional particle flow code (PFC3D), and a triaxial loading scheme with a single free surface was applied to investigate the effects of free-surface rock properties, support parameters, and confining pressure on the load-bearing performance of the layered rock mass. The main findings are as follows: (1) Without support, the ultimate bearing capacity of a hard-rock-free-surface specimen is about 1.2 times that of a soft-rock-free-surface specimen. Applying support strengths of 0.2 MPa and 0.4 MPa enhanced the bearing capacity by 29–38% and 46–75%, respectively. (2) The evolution of axial stress in the bolts reflects the migration of the load-bearing core of the anchored body. Enhancing support strength improves the stress state of bolts and effectively mitigates the effects of high-stress conditions. (3) Under loading, soft rock layers exhibit greater deformation than hard layers. A hard-rock free surface effectively resists extrusion deformation from deeper soft rocks and provides higher bearing capacity. Shallow free-surface failure is significantly suppressed in anchored bodies, and “compression arch” zones are formed within multiple layers due to bolt support. Full article

With coal mines’ mining depth increasing, the stress environment in deep mining (including key factors such as high ground stress, strong disturbance, and complex geological structures, as well as stress redistribution after deformation of surrounding roadway rock) is complex, which leads to increasingly prominent deformation and failure problems for goaf-side roadways in thick coal seams. Surrounding rock deformation is difficult to control, and mine pressure behavior is violent, making traditional support technologies no longer able to meet the mining safety requirements of roadways in deep thick coal seams. Taking the 6311 working face of Tangkou Coal Mine as the engineering research background, this paper systematically summarizes the deformation and failure characteristics of goaf-side roadways in deep thick coal seams through field monitoring, borehole peeping, and other means, and conducts in-depth analysis of their failure mechanisms and influencing factors. Aiming at these problems, a synergistic support–unloading control method for goaf-side roadways is proposed, which integrates roof blasting pressure relief, coal pillar grouting reinforcement, and constant-resistance energy-absorbing anchor cable support. The effects of the unsupported scheme, original support scheme, and synergistic support–unloading control scheme are compared and analyzed through FLAC^3D numerical simulation. Further verification through field application shows that it has remarkable effects in controlling roadway convergence deformation, roof separation, and bolt (cable) stress. Specifically, compared with the original support schemes, the horizontal displacement on the coal pillar side is reduced by 89.5% compared with the original support scheme, and the horizontal displacement on the solid coal side is reduced by 79.3%; the vertical displacement on the coal pillar side is reduced by 45.8% and the vertical displacement on the solid coal side is reduced by 42.4%. Compared with the original support scheme, the maximum deformation of the roadway’s solid coal rib, roof, and coal pillar rib is reduced by 76%, 83%, and 88%, respectively, while the separation between the shallow and deep roof remains at a low level. The coal stress continues fluctuating stably during the monitoring period; the force on the bolts (cables) does not exceed the designed anchoring force, with sufficient bearing reserve space (47% remaining), and no breakage occurs, which fully proves the feasibility and effectiveness of the synergistic support–unloading control technology scheme. This technology realizes the effective control of on-site roadways and provides technical reference for the support engineering of coal mine goaf-side roadways under similar conditions. Full article

This study presents an expert system for assessing the stability of underground mine workings and automatically selecting rock bolt support schemes. The system integrates physically based calculations of roof compressive strength (Rc) and expected maximum displacement (Um) with rule-based decision logic grounded in engineering practice. Unlike empirical classifications and black-box AI models, the proposed approach ensures interpretable, reproducible, and context-aware engineering decisions. The architecture includes a numerical solver that computes Rc and Um based on excavation geometry, geomechanical properties, and mining conditions. The support scheme is selected using a knowledge base of formalized rules, while the specific support parameters are calculated within the solver. The system was validated across 51 underground excavations, with approximately 85% of its recommendations matching field-proven support solutions, and 12% suggesting reinforced schemes that could have prevented failures. The expert system is suitable for integration into digital mine management platforms and offers a foundation for developing digital twin solutions in geomechanically variable environments. Full article

Addressing the stability control challenges of roadways with composite roofs in the No. 34 coal seam of Donghai Mine under high-strength mining conditions, this study employed integrated methodologies including laboratory experiments, numerical modeling, and field trials. It investigated the mechanical response characteristics of the composite roof and developed a synergistic control system, validated through industrial application. Key findings indicate significant differences in mechanical behavior and failure mechanisms between individual rock specimens and composite rock masses. A theoretical “elastic-plastic-fractured” zoning model for the composite roof was established based on the theory of surrounding rock deterioration, elucidating the mechanical mechanism where the cohesive strength of hard rock governs the load-bearing capacity of the outer shell, while the cohesive strength of soft rock controls plastic flow. The influence of in situ stress and support resistance on the evolution of the surrounding rock zone radii was quantitatively determined. The FLAC^3D strain-softening model accurately simulated the post-peak behavior of the surrounding rock. Analysis demonstrated specific inherent patterns in the magnitude, ratio, and orientation of principal stresses within the composite roof under mining influence. A high differential stress zone (σ₁/σ₃ = 6–7) formed within 20 m of the working face, accompanied by a deflection of the maximum principal stress direction by 53, triggering the expansion of a butterfly-shaped plastic zone. Based on these insights, we proposed and implemented a synergistic control system integrating high-pressure grouting, pre-stressed cables, and energy-absorbing bolts. Field tests demonstrated significant improvements: roof-to-floor convergence reduced by 48.4%, rib-to-rib convergence decreased by 39.3%, microseismic events declined by 61%, and the self-stabilization period of the surrounding rock shortened by 11%. Consequently, this research establishes a holistic “theoretical modeling-evolution diagnosis-synergistic control” solution chain, providing a validated theoretical foundation and engineering paradigm for composite roof support design. Full article

To elucidate evolutionary characteristics of the surrounding rock failure mechanism in a double-roadway layout, this work is grounded on in the research context of the Jinjitan Coal Mine, focusing on the deformation and failure mechanisms of double roadways. This paper addresses the issue of resource wastage resulting from the excessive dimensions of coal pillars in prior periods by employing a research methodology that integrates theoretical analysis, numerical simulation, and field monitoring to systematically examine the movement characteristics of overlying rock in the working face. On that basis, the size of coal pillar is optimized. The advance’s stress transfer law and deformation distribution characteristics of the return air roadway and transport roadway are studied. The cause of the asymmetric deformation of roadway retention is explained. A differentiated design is conducted on the support parameters of double-roadway bolts and cables under strong dynamic pressure conditions. The study indicates that a 16 m coal pillar results in an 8 m elastic zone at its center, balancing stability with optimal resource extraction. In the basic top-sloping double-block conjugate masonry beam structure, the differing stress levels between the top working face’s transport roadway and the lower working face’s return air roadway are primarily due to the varied placements of key blocks. In the return air roadway, floor heave deformation is managed using locking anchor rods, while roof subsidence is controlled with a constant group of large deformation anchor cables. The displacement of surrounding rock increases under the influence of both leading and lagging pressures from the previous working face, although the change is minimal. There is a significant correlation between roadway deformation and support parameters and coal pillar size. With a 16 m coal pillar, differential support of the double roadway lowers the return air roadway deformation by 30%, which improves the mining rate and effectively controls the deformation of the roadway. Full article