- WANG Jiachen;LIU Yunxi;ZHANG Wei;WANG Zhaohui;CHEN Kun;WANG Shirong;LI Zijian;ZHENG Canzhe;ZHANG Dingtang;School of Energy and Mining Engineering, China University of Mining and Technology-Beijing;Jinjitan Coal Mine, Shaanxi Future Energy and Chemical Co., Ltd.;Zhengzhou Coal Mining Machinery (Group) Co., Ltd.;
ully-mechanized top-coal caving with large-cutting-height(LC-HTCC) is a key technology for the safe and efficient mining of ultra-thick coal seams. However, the exceptionally large mining space intensifies the inherent contradiction between wall stability and the cavability of hard top coal. This conflict becomes particularly acute when both the coal seam and the immediate roof are highly competent, significantly limiting the potential for achieving super-high production rates. Taking Panel 111 of the Jinjitan coal mine as a case study,theoretical analysis, laboratory testing, numerical simulation and in-situ monitoring were performed to investigate the coupled failure mechanism of the high rib and hard top coal under these challenging geological conditions. A structural model of the support–surrounding rock system is established, and analytical expressions for support resistance and rib pressure under massive hard-roof impact are derived, demonstrating that support stiffness governs load transfer within the roof. By applying the principle of minimum potential energy, the ultimate bearing capacities of the high rib and hard top coal are determined, and the conditions for coupled instability, cooperative stability and asynchronous response are clarified. Stability and cavability indices are defined and found to change with the cutting-to-caving ratio according to a negative exponential law, quantitatively characterizing the negative feedback between rib stability and top-coal cavability. A synergistic control strategy was developed, incorporating massive hard-roof fracturing, high-strength/high-stiffness support, optimization of the cutting-to-caving ratio, and face layout redesign. Field implementation resulted in a 60% reduction in rib damage and a top-coal recovery rate of 83%, enabling the safe and efficient extraction of an ultra-thick coal seam using the LC-HTCC method.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2390K] - WU Yongzheng;HE Sifeng;FU Yukai;ZU Guoli;ZHANG Heng;LI Junchen;Coal Mining Branch, China Coal Research Institute;CCTEG Coal Mining Research Institute;School of Energy and Mining Engineering, China University of Mining and Technology-Beijing;
To address the challenge of managing surrounding rock deformation in deep rockburst roadways, this study utilizes the 402101 working face of a coal mine as the engineering background. Through a combination of field investigation, theoretical analyses, numerical simulations and industrial tests, the instability characteristics of the roadway, identifies the primary controlling factors was examined, and the stress transfer mechanisms under static-dynamic loading conditions was elucidated. A novel "bolt-U typed steel support-filling(BUF)" synergetic control technology is proposed and subsequently validated through practical engineering applications. The results show that the principal factors contributing to surrounding rock instability include the interaction of high staticdynamic loads, the inadequate impact resistance of support materials and the poor synergy within the support system. The BUF system establishes a composite bearing structure by employing pre-stressed anchor cables(to control crack propagation), the yielding of U-typed steel supports(to facilitate energy conversion), and the uniform energy dissipation provided by the filling layer. In accordance with the theory of surrounding rock structure stratification, the surrounding rock of the roadway is categorized into three layers: the support layer, the anchoring layer and the original rock layer. The compressive stress of the support layer is influenced by the rockburst failure coefficient k_b, the dimensions of the roadway, the physical properties of the surrounding rock and the support resistance provided by bolts and cables. An impact risk assessment methodology is developed,focusing on the relationship between the compressive stress and the strength of the support layer. Computational examples reveal that the BUF system can decrease the compressive stress of the support layer by 18.5% to 42.1%and withstand dynamic load disturbances at k_b=2.0. Numerical simulation results indicate that in comparison to conventional support systems, the BUF system reduces the plastic zone by 79.1%, decreases the displacement of the roof and sidewalls by nearly 90%, fully activates the passive bearing capacity of the supports, and optimizes the energy field distribution. In practical engineering applications, the maximum displacement of the surrounding rock controlled by the BUF system is 43 mm, and the maximum stress on the supports is 0.34 MPa. The structure remains stable, thereby effectively ensuring safe and efficient mining operations.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2533K] - LIU Jianfeng;WEI Jinbing;DAI Jingjing;XUE Fujun;WANG Lei;TANG Yifan;YANG Jianxiong;College of Water Resources and Hydropower, Sichuan University;GFZ German Research Center for Geosciences, Helmholtz Center;
Fluid injection-induced seismicity has garnered global attention, causing a key technical challenge to the safe extraction of clean energy resources, such as shale gas. Taking a representative shale gas development area in the southern Sichuan Basin as the background, this study investigated the evolution and fluctuation of seismicity parameters during fluid injection, and examined the spatiotemporal dynamics of the seismic front and back-front behavior. The underlying fluid-driven patterns of earthquake swarms in the region were explored. The results show a clear spatiotemporal correlation between fluid injection and moderate-to-strong earthquakes(M_L ≥3.5), with the injection process significantly enhancing the intensity and complexity of seismicity. We confirm the ubiquity of the seismic back-front phenomenon, characterized by a progressively expanding central zone devoid of seismicity. The seismic front and back-front are found to be controlled by aseismic slip, while the swarms between them are governed by a combination of mechanisms: alternating dominance of slow diffusion driven by fluid pressure and rapid migration driven by aseismic slip. These findings helps the understanding of the physical origins of fluid-induced seismicity in shale gas regions, as well as for assessing and mitigating associated seismic hazards.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2373K] - WANG Kai;ZUO Xiaohuan;DU Feng;SUN Jiazhi;ZHANG Junwen;LI Kangnan;ZHANG Xiang;Inner Mongolia Research Institute, China University of Mining and Technology-Beijing;Beijing Key Laboratory for Precise Mining of Intergrown Energy and Resources, China University of Mining and Technology-Beijing;School of Emergency Management and Safety Engineering, China University of Mining and Technology-Beijing;Faculty of Public Security and Emergency Management, Kunming University of Science and Technology;School
It is of significant importance to investigate the energy evolution characteristics and progressive damage behavior of gas-bearing coal-rock combinations under both conventional and graded cyclic loading conditions for the prevention and control of deep coal-rock-gas composite dynamic disasters. By laboratory testing and theoretical analysis, a series of coupled acoustic emission(AE)-seepage-damage triaxial tests were conducted under various confining pressures and stress paths. The mechanical response, progressive damage behavior, and energy evolution patterns of loaded gas-bearing coal-rock combinations were systematically analyzed. By combining macro-meso failure characteristics, the influence mechanisms of confining pressure and stress loading on the failure behavior of gas-bearing coal-rock combinations were revealed. The results show that the peak strength, elastic modulus and residual strength of the composite specimens increase linearly with confining pressure. Under the same confining pressure, the elastic modulus under graded cyclic loading is lower by 0.13-1.76 GPa, and the peak strength is lower by 8.91%-20.81% than those under the conventional triaxial loading. Increasing confining pressure significantly suppresses crack development, while graded cyclic loading exhibits the lower crack initiation stress and damage stress ratios, making specimens more prone to cracking at lower stress levels. Acoustic emission(AE) signals exh.ibit stage-wise variations corresponding to characteristic stresses during progressive damage. Peak acoustic emission counts increase with higher confining pressure.Elevated confining pressure restricts internal crack propagation and coalescence. Under graded cyclic loading, the Kaiser effect zone of acoustic emission counts extends, while the Felicity effect zone shortens. The total energy,elastic energy and dissipated energy under graded cyclic loading are all higher than those under conventional triaxial loading. Energy dissipation is more pronounced in intervals with the larger stress amplitudes. SEM observations reveal more complex and rougher failure surfaces under graded cyclic loading, with more evident cracks and pores, and fractal dimension values larger by 0.057-0.280 than that under conventional triaxial loading. High confining pressure induces greater damage effects than compressive restrictions, exacerbating interfacial failure in coal-rock combinations, with shear failure being the dominant failure mode. These findings provide a theoretical basis for preventing and controlling coal and gas composite dynamic disasters in high-stress and high-gas-pressure zones in deep coal mining.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 6331K] - YANG Ke;ZHENG Shizhang;LUO Xiaoyong;LIU Wenjie;XU Rijie;State Key Laboratory of Deep Coal Mining and Environmental Protection, Anhui University of Science and Technology;School of Mining Engineering, Anhui University of Science & Technology;Dingji Coal Mine, Huaihu Coal Electricity Co., Ltd.;
Quantitatively describing the development of mining-induced fractures and the evolution of permeability in the double key strata is crucial for the efficient gas extraction from the gob area and fracture zone.Taking the Dingji Coal Mine in the Huainan mining district as the engineering background, numerical simulations were conducted to study the dynamic evolution of overburden fractures during mining under the double key strata. The fracture density and fracture ratio are quantitatively analyzed using a grid-based image division method. Fractal theory is introduced to describe the propagation and closure processes of mining-induced fractures beneath the deep double key strata. Based on the fracture characteristic parameters, a fractal seepage model for overburden fractures is derived, and an optimized criterion for target layer selection in high-extraction tunnels is proposed. The study results show during the deep coal seam mining under double key strata, the mininginduced fractures develop upward and forward as the working face advances. In the horizontal direction, fractures in the center of the gob area are small and dense, while fractures in the working face and drifts are large and sparse. In the vertical direction, fractures below Key Stratum 2 maintain their integrity for a long period, and the fracture area and fractal dimension are greater than those in other strata, indicating that the key strata play a protective role in fracture distribution. According to the fractal seepage model for mining-induced fractures, the overburden permeability is in the range of 10~(-14)～10~(-11) m~2. The permeability distribution follows an "unimodal"-"terraced"-"saddle-shaped" evolution pattern as the working face progresses. After mining, a narrow low-permeability zone forms above Key Stratum 1, and the permeability below Key Stratum 2 reaches its maximum value, exceeding 1×10~(-11) m~2, demonstrating that the double key strata indirectly control the distribution of overburden permeability. The main factors influencing the gas extraction efficiency in high-extraction tunnels include the gas source, gas channels, and tunnel stability. Considering these factors, a concept of an effective gas extraction coefficient for high-extraction tunnels is quantitatively defined from three aspects: the degree of gas accumulation, the duration of high-permeability zones, and tunnel stability. An optimized criterion for selecting target layers for high-extraction tunnels is proposed, and.it is applied in a trial working face, achieving good gas extraction results. The research findings provide valuable reference for the study of mining-induced fracture seepage evolution in deep coal seams under double key strata and guide the layout planning of high-extraction tunnel layers in mines.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 8159K] - XU Gang;ZHANG Zhen;FENG Yanjun;HUANG Zhizeng;ZENG Mingsheng;LIU Qianjin;LIU Xiaogang;LIN Xingyu;MA Rongshan;LI Zhengjie;Coal Mining and Designing Department, Tiandi Science and Technology Co., Ltd.;CCTEG Coal Mining Research Institute;Key Laboratory of National Mine Safety Supervision Bureau for Mine Roof Disaster Prevention and Control;State Key Laboratory of Intelligent Coal Mining and Strata Control;
The successful mining of working face of 10 m ultra-large mining height in Caojiatan Coal Mine marks a new stage for the fully-mechanized mining of extra-thick coal seams. Based on multi-source monitoring data,such as mine pressure, displacement and microseismics, the rules of mine pressure behavior and the occurrence mechanism of strong mine pressure in the 10 m ultra-high mining height working face were studied, and a "superimposed arch-beam" structural model of the ultra-high mining height stope was established. A three-in-one surrounding rock control strategy of "active support and protection + regional pressure relief and weakening + allround monitoring and early warning" was proposed. The results show that the cyclic breaking of the overlying rock in the 10 m ultra-high mining height working face has the characteristics of strong mine pressure, such as strong dynamic load, fast roof sinking speed, long lasting distance of pressure, and high opening rate of support safety valves. The cyclic breaking of the roof of the working face is 10-25 m, the average dynamic load coefficient of periodic pressure is 1.42, and the average maximum shrinkage of support is 0.63 m. During the pressure period, the proportion of hydraulic support safety valves opening rate was more than 50% is 48.1%. The incoming pressure shows regional aggregation characteristics along the tendency direction, distributed in the range of 75-250 m from the nose. The trend direction shows the characteristics of alternating incoming pressure with "large and small cycles", and the average interval between large cycles is 137.5 m. The overlying rock strata of the ultra-high mining face are in a superimposed "a.rch-beam" structure, and the thick and hard roof in the middle and upper parts overhangs the roof behind the goaf for a long distance, causing the roof to break in front of the face or bend and sink behind the support, causing strong mine pressure appears in face. Reducing the step distance and continuous distance of periodic weighting, reducing the dynamic load coefficient of weighting support, preventing coal wall spalling and avoiding the crushing of hydraulic support are the core elements to control the stability of surrounding rock in 10 m ultra-large mining height working face. The high initial supporting force characteristics of the hydraulic support effectively control the early subsidence of the roof, the high working resistance characteristics relieve the bearing capacity of the coal wall, inhibit the large-area spalling of the coal wall and the rapid subsidence of the roof during pressurization effectively. The double-layer telescopic beam structure of the hydraulic support is combined with the three-level linkage protection device, which realizes the coordinated control of the unsupported area of the roof in front of the support and the protection operation of the ultra-high coal wall, and effectively overcomes the defects of the insufficient protection coverage of the coal wall of the original split protection device. The 5 m~3/min high-flow hydraulic fracturing technology, employing a "one-field-one-strategy" zonal parameter design, effectively weakens the thick hard roof, leading to a significant reduction in weighting intervals and dynamic loading coefficients. The real-time warning system of KJ21 mine pressure achieves dynamic monitoring of support operating conditions and roof fracturing.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2914K] - ZHANG Yujun;SONG Yejie;HU Haoyu;ZHANG Fengda;ZHANG Zhiwei;LI Youwei;XIAO Jie;LI Jiawei;CCTEG Coal Mining Research Institute;Coal Mining and Designing Department, Tiandi Science and Technology Co., Ltd.;Mining Research Branch, China Coal Research Institute;State Key Laboratory of Intelligent Coal Mining and Strata Control;
For water hazard prevention and control as well as water resource protection in typical mining areas with thick and extremely thick coal seams under water-bearing strata, nearly 30 years of practical experience in mining under water-bearing strata were summarized and refined. This has led to the development of a water control(protection) technology model suitable for typical mining areas in China. Based on the occurrence characteristics of water-bearing roof in typical mining areas and the spatial relationship with the main coal seam,five water filling models were proposed, that is, weakly consolidated water sand collapse, high pressure progressive water filling, high-positioned thick water-bearing strata permeation, upward and downward cracks progressive conduction water filling, and lateral large channel strong recharge water filling. Based on the dual control of disturbance range and water filling volume, an integrated theory and technical system for controlled(protecting) water in coal mine roof water-bearing strata were established, including precise detection of water-bearing strata, precise control of overburden damage, controllable reduction of water filling volume, and coordinated monitoring and early warning of hydro logical conditions. Key technologies were proposed, such as precise detection using transient electromagnetic methods considering shutdown time effects, height estimation of high-intensity mining-induced conductive fracture zones in thick and extremely thick coal seams, pre-mining precise pre-reduction of roof water-bearing strata based on drainage capacity constraints, weakening hard main control overburden to guide the height of conductive fracture zones, and hydrological monitoring and early warning involving three parameters of absolute value, change rate and trend of water level in water-bearing strata.For the water control practice of roof water-bearing strata in some typical mining areas in China, corresponding water control mining models have been proposed, achieving sucess in water control for mining under different types of water-bearing strata. The research findings provide scientific reference for coal mining under water-bearing strata, realizing safe, efficient and green mining.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2392K] - TAO Zhigang;YU Haijun;LEI Xiaotian;YANG Xiaojie;LI Yong;GUO Aipeng;HUO Shusen;YUAN Bo;ZHANG Yanyang;State Key Laboratory for Tunnel Engineering, China University of Mining and Technology-Beijing;School of Mechanics and Civil Engineering, China University of Mining and Technology-Beijing;College of Mining Engineering, North China University of Science and Technology;College of Geoscience and Surveying Engineering, China University of Mining and Technology-Beijing;National Institute of Natural Haz
Large deformation of surrounding rock is a great challenging in soft rock underground engineering. We analyzed the microscopic and pore characteristics of typical surrounding rock using scanning electron microscopy(SEM) and established a mechanical model for high pre-stressed long and short anchor cables in a collaborative support system. By integrating test results of surrounding rock loose zones and calculations of surrounding rock pressure, the support parameters for long and short anchor cables are determined and verified. A suitable support scheme for large deformation sections using high pre-stressed long and short anchor cables is proposed.Additionally, numerical simulation techniques are employed to systematically analyze the large deformation of surrounding rock and the supporting mechanism of long and short anchor cables under tectonic stress. The results reveal that the surrounding rock of the DLⅡ11 + 080 section of the branch tunnel of Haidong Tunnel is primarily composed of calcareous shale, characterized by developed fractures, high porosity, and a loose structure. The microscopic layered structure contributes to the rock's fragility, making it susceptible to external forces. Single-length short anchor cable support is ineffective in providing adequate reinforcement to the surrounding rock.However, the use of both long and short anchor cables enhances support by leveraging their synergistic effects.The short anchor cable primarily mitigates early plastic deformation, while the long anchor cable provides overall constraints to prevent the expansion of deep displacement. Through numerical simulations, the plastic zone and convergence deformation of surrounding rock are analyzed under varying lateral pressure coefficients and cohesion levels. The study also elucidates the influence of tectonic stress and surrounding rock strength on tunnel deformation. The results indicate that the depth of the vault plastic zone under the optimized long and short anchor cable support is 48.63% lower than without any support and 44.38% lower compared to support using 6-meter short anchor cables alone. The combined support of long and short anchor cables significantly enhances the uniformity of axial force distribution, improves the ove.rall support effect, and stabilizes the surrounding rock.This research provides a scientific foundation and practical guidance for controlling large deformations under tectonic stress in soft rock underground engineering.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2702K] - LI Yuancheng;WANG Bo;LI Yongming;MA Pengfei;NIE Lichao;ZHANG Weiping;LI Jun;State Key Laboratory for Tunnel Engineering, Shandong University;Institute of Geotechnical and Underground Engineering,Shandong University;China Power Construction Group Guiyang Survey Design and Research Institute Co., Ltd.;Yunnan Aerospace Engineering Geophysical Detecting Co., Ltd.;
River embankments often suffer from weak foundation conditions, making them susceptible to seepage, piping and slope failures during flood seasons. Regular, rapid and accurate inspections are essential for ensuring the safe operation of embankments. As an effective non-destructive geophysical technique, Ground Penetrating Radar(GPR) has been widely applied in potential hazard detection in embankments. However, raw GPR signals often contain considerable high-frequency noise and background interference, making it difficult to extract reliable features under complex field conditions. Traditional spectral analysis methods, such as the Fourier Transform, typically suffer from spectral smearing and unclear dominant frequency components, limiting their practical application. To address these limitations, a three-dimensional spectral energy ratio imaging method was proposed for potential embankment hazard detection based on combined wavelet-fourier transforms. In this approach, wavelet transform is first applied to analyze non-stationary and transient components of the radar signal, allowing for multiscale decomposition of its frequency characteristics. Subsequently, a short-time Fourier transform is used to calculate the temporal evolution of frequency-domain information and extract dominant frequency components and energy distribution across time windows. Based on this, a classification criterion of hazard types is developed using the spectral energy ratio, enabling the effective separation of loose zones and water-enriched zones within the embankment. This approach facilitates high-resolution, efficient and non-destructive identification of internal embankment anomalies. Finally, a field investigation was carried out on the triangular joint polder embankment in Yongxiu County, Jiujiang City, Jiangxi Province. The results demonstrate that the proposed method successfully detects and delineates loose and water-rich areas within the embankment,indicative for hazard assessment and routine inspection of earthen dams.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2273K] - JIANG Song;WEI Yu;RAO Binjian;YAN Peitao;WANG Huijie;LIU Zhongguang;GU Qinghua;School of Resources Engineering, Xi'an University of Architecture and Technology;Sinosteel Ma′anshan General Institute of Mining Research Co., Ltd.;School of Management, Xi'an University of Architecture and Technology;Sinosteel Fuquan Mining Co., Ltd.;Sinosteel Group Chifeng Jinxin Mining Co., Ltd.;
The joints and fissures produced by the surface deterioration of rock slopes in open pit mines are the key factors inducing landslides, and timely and accurate fissure detection is an important prerequisite for mining safety. Aiming at the problems of single fissure morphology generated by traditional data enhancement algorithms and the existing slope fissure monitoring methods being limited to local image analysis, a method for detecting fissuress in rock slopes of large-scale open-pit mines using Copy-Paste algorithm has been proposed, in which the fissure morphology is augmented by the Copy-Paste algorithm, and then a three-phase system workflow is established with sliding window algorithm-U-Net accurate segmentation-panoramic feature stitching to overcome the problems of lost and false detection of fissure features in large-scale scenes. The experimental results show that the proposed scheme results in a significant increase in the diversity of cleft samples, and the algorithm achieves 0.22% and 0.85% improvement in the segmentation IoU metrics when compared to the Mask R-CNN and U-Net models using traditional data enhancement, respectively. The slope project of Luoyang Luanchuan Longyu Molybdenum Mine is used for validation, showing the proposed three-phase system workflow has a positive role in promoting the identification and segmentation effect of large-scale fissures, with the mIoU value significantly increasing by 7.09% compared to that the three-phase system workflow is not used. The proposed scheme provides a new technical approach for disaster warning in steep rock slope engineering.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2753K] - YAN Junsheng;LIU Zaibin;YANG Hui;WU Mouda;ZHANG Yongtao;ZHOU Duidui;LI Peng;LIU Wenming;Xi'an CCTEG Transparent Geology Technology Co., Ltd.;CCTEG Xi'an Research Institute(Group)Co., Ltd.;State Key Laboratory of Digital Intelligent Technology for Unmanned Coal Mining;China Coal Research Institute;Shaanxi Binchang Mining Group Co., Ltd.;Shaanxi Binchang Dafosi Coal Mine Co., Ltd.;
As a crucial geological structure in coal mine, faults directly affect the stability of mining operations and the occurrence of fault-related disasters. To address the current limitation that mine-scale fault complexity assessments cannot effectively quantify the impact of faults on working face operations, a new method is proposed by integrating transparent geological model with numerical simulation to calculate the three-dimensional(3D) faults complexity at the working face scale. On one hand, based on a transparent geological model of the working face, the spatial curvature features of fault plane are extracted through mathematical analysis using recursive search algorithms and the least squares method. On the other hand, a numerical model of the fault-containing working face is constructed using the Anderson fault model and the Mohr-Coulomb(M-C)failure criterion. This model simulates the regional stress accumulation patterns in the rock mass under mining conditions, reflecting the degree of fault zone activation. Subsequently, the entropy weight method is used to integrate the two types of fault features, compensating for the statistical characteristics of the fault structure. The 3D fractal dimension is then employed as the framework to compute the overall 3D faults complexity of the working face under mining-induced conditions. Taking the 40103 working face in the Dafosi Coal Mine of the Binchang mining area as the engineering background, the 3D complexity of fault was calculated at mining distances of 100, 80, 60, 40, 20 and 0 m from the DF5 reverse fault. Combined with fault spatial distribution and microseismic data, the variation trends of fault complexity at different mining positions were analyzed. The results indicate that the overall 3D fault complexity increases as mining approaches the DF5 reverse fault. The complexity changes mainly because the fault enters a.n unstable state during mining, which propagates both laterally and longitudinally as the mining face advances-particularly when approaching the fault. Additionally,zones with intersecting multiple faults are more strongly affected by mining disturbances than those with a single fault, with fault structures evolving from single to intersecting patterns. Furthermore, high-energy microseismic events are predominantly concentrated in areas of higher fault complexity. The evolution of these events closely mirrors the trend of increasing fault complexity, indicating that the more structurally complex a fault is, the more uneven the spatial distribution of microseismic events and the higher the frequency of high-energy occurrences.This highlights the correlation between changes in regional rock stress and the fault instability state reflected by the 3D faults complexity model under mining conditions.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2095K] - DONG Shuangyong;KANG Hongpu;GAO Fuqiang;LOU Jinfu;LIU Wenju;WANG Xiaoqing;LU Zhiguo;PENG Xiangyuan;Coal Mining Branch, China Coal Research Institute;State Key Laboratory of Intelligent Coal Mining and Strata Control;CCTEG Coal Mining Research Institute;
Confining stress is one of the key factors affecting the anchoring performance of rockbolts. To investigate the effect of confining pressure on rockbolt anchoring performance and its influencing factors, the anchor pull-out tests under the conditions of the surrounding rock properties and stress environment were carried out using the self-developed rockbolt confining pressure pull-out test device. The influence of factors, such as confining pressure, rockbolt diameter, anchoring length and surrounding rock strength, on the anchoring performance of rockbolts was investigated. The results show that confining pressure is a critical factor influencing rockbolt anchoring performance. With increasing confining stress, the lateral constraint exerted by the surrounding rock on the anchoring interface strengthens, leading to an approximately linear increase in the ultimate anchoring force of the rockbolt at a rate of 4.28 kN/MPa. This manifests as a significant improvement in the overall bearing capacity of the rockbolt anchoring system. Under constant confining pressure, the rockbolt diameter and anchoring length exhibit a positive correlation with the ultimate anchoring force. The larger rockbolt diameters and longer anchoring lengths enhance the anchoring force more effectively, although this enhancement is limited by the material strength of the rockbolt and the bearing capacity of the surrounding rock. The anchoring performance of rockbolt is highly sensitive to the strength of the surrounding rock. Under the same confining stress, the anchoring force of rockbolt is positively correlated with the strength of the surrounding rock, and the stronger surrounding rock provids better anchoring conditions and greater system stability. Furthermore,recommendations to improve rockbolt anchoring performance in coal mine roadway support were proposed,which is valuable for the design and optimization of deep coal mine roadway support under complex geological conditions.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2038K] - LUAN Hengjie;JIA Zhiwei;ZHANG Sunhao;GUO Yao;JIANG Yujing;LIU Jianrong;WANG Dong;College of Energy and Mining Engineering, Shandong University of Science and Technology;Academician(Expert)Workstation, Inner Mongolia Shanghaimiao Mining Co., Ltd.;China Coal Society;
To study the damage and deterioration characteristics of coal-rock combinations with the same fractures under cyclic loading, experiment and numerical simulation were conducted to investigate the effects of coal-rock ratio and cyclic loading amplitude on the damage evolution and macro-micro failure mechanisms of rock-coal-rock combinations. The results show that the coal fracture network dominates the strength and failure of the combination. During the cyclic loading and unloading process, the stress-strain curve shows a hysteresis effect, which is small and dense at the initial stage and large and sparse at the later stage. The displacement changes sinusoidally with time, and the overall displacement increases in the first few cycles before instability.When the force on the particles is greater than the particle bonding strength, cracks first initiate at the tip of the coal fractures, and then the force concentration point shifts to the surrounding particles, causing the cracks to develop in a band-like manner. Multiple sets of crack bands and fracture zones coalesce through crack bands,causing the specimen to lose its load-bearing capacity. As the proportion of coal in the combination increases, the strength of the combination decreases, the displacement increases, the b value of acoustic emission decreases, and the number of cycles before instability decreases. As the cyclic loading amplitude increases, the displacement of the combination increases, the b value of acoustic emission decreases, the degree of deterioration of the combination deepens, and it is more likely to cause instability of the combination specimen.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 5546K] - CHI Xiaolou;ZANG Desong;FENG Yanjun;ZHAO Kaikai;LYU Xin;FAN Chaochen;FU Qiang;School of Mining Engineering, Anhui University of Science and Technology;State Key Laboratory for Safe Mining of Deep Coal Resources and Environment Protection, Anhui University of Science and Technology;CCTEG Coal Mining Research Institute;National and Local Joint Engineering Research Center of Precision Coal Mining, Anhui University of Science and Technology;
Taking the thick overlying roof of the 122104 working face in the Caojiatan Coal Mine as the research background, prefabricated crack models of different heights was prepared and CT-based in-situ uniaxial compression tests were conducted to investigate the mechanical characteristics of specimens with prefabricated cracks of different heights, along with their mechanical damage and degradation processes. The experimental results show that compared with intact specimens, the peak strength, acoustic emission energy, total strain energy,elastic strain energy and post-peak strain energy of the prefabricated crack specimens are significantly reduced.The energy dissipation index of the upper, middle, and lower crack specimens increased by 24.7%, 28.5%, and 62.6%, respectively. The strength degradation index increased by 21.9%, 28.1%, and 54.6%, respectively, and the impact energy index decreased by 19.9%, 20.9%, and 49.5%, respectively. Among them, the lower-crack specimen shows the best pressure relief effect, with the lowest initial kinetic energy upon failure. The crack initiation times for the intact specimen and the specimens with upper, middle and lower prefabricated cracks are 89, 44, 42, and 39 s, respectively. The failure mode shifts from tensile-splitting failure in the intact specimen to tensile-shear composite failure in the cracked specimens. As the crack height decreases, the initiation and development of cracks occur earlier, with increased microcracks and rock debris at the fracture surfaces. In the lower-crack specimen, the surface porosity, maximum pore area and probability entropy of the fracture increased by 98.51%, 317.58%, and 5.38%, respectively. Based on the analysis of failure characteristics of specimens with prefabricated cracks at different heights, the damage degradation mechanism is revealed from the perspective of hindered force chain transmission. The findings is indicative for optimizing the selection of pressure-relief stratification in thick roof areas.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 3089K] - LIU Gang;WANG Shengxuan;WANG Dongwei;ZAN Yonglong;Heilongjiang Ground Pressure & Gas Control in Deep Mining Key Lab, Heilongjiang University of Science and Technology;College of Mining Engineering, Heilongjiang University of Science and Technology;Baotailong New Materials Co., Ltd.;
To study the influence of non-uniform stress on rock damage, failure and the evolution law of damage zones, the mechanical response characteristics and energy evolution law of sandstone with defects under non-uniform stress were studied. The results show that the stress-strain curve stage in the low-stress area is highly consistent with the overall curve of the specimen, and the residual stress fluctuation characteristics of sandstone are highly consistent with the curves in the high and low stress areas. The higher the overall bearing capacity of sandstone, the greater the peak difference between stress areas. It is also found that in the high-stress area, circular defect sandstone shows low stress and high deformation at the peak, while trapezoidal and rectangular defect sandstone shows high stress and low deformation at the peak. In the low-stress area, the initial deformation field is prone to intersect, and trapezoidal defect sandstone has the largest radial deformation, circular defect sandstone has the largest axial deformation, and rectangular defect sandstone has the smallest. In the high-stress area, the strain curve contracts inward, while it expands outward in the low-stress zone. The acoustic emission ring count of sandstone with rectangular and circular defects shows a first increasing, then decreasing, and final increasing trend, while that of trapezoidal defect sandstone shows a continuous increase and sudden increases at multiple points, showing an overall dense-sparse-dense change pattern. In the initial stage, sandstone with rectangular defect generates more shear cracks, while sandstone with circular and trapezoidal defects generates fewer cracks.With the increase of stress, the number of shear cracks in the three defect shapes of specimens shows an increasing trend, and the failure mode of sandstone is mainly shear failure. In the high-stress area, there are more shear cracks and they are more likely to form coalesced cracks, while in the low-stress area, there are fewer cracks and they are mostly tensile cracks. The efficiency proportion in the high-stress area is higher than that in the low-stress area, and the proportion of elastic deformation ene.rgy in the low-stress area is higher than that in the high-stress area, especially in the specimen with circular defect shape. Energy dissipation in high-stress regions shows a steady increase, while growth in low-stress regions slows. The dissipation energy accumulation curve in high-stress zone shows a sequential trend of acceleration, uniform speed and deceleration trend, while the dissipation energy of the low-stress zone shows a sequential trend of acceleration, deceleration and acceleration trend.
2025 05 v.7;No.32 [Abstract][OnlineView][Download 2629K]
2025 05 v.7;No.32 [Abstract][OnlineView][Download 216K]