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Optimal mining sequence for coal faces under a bedding slope:insight from landslide prevention

Journal of Mountain Science 2024年第5期21卷 1775-1798页

作者： LI Qingmiao ZHAO Jianjun LI Zhichao DENG Jie ZUO Jing LAI Qiyi state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu 610059China

Repetitive mining beneath bedding slopes is identified as a critical factor in geomorphic disturbances, especially landslides and surface subsidence. Prior research has largely concentrated on surface deformation in plains due to multi-seam coal mining and the instability of natural bedding slopes, yet the cumulative impact of different mining sequences on bedding slopes has been less explored. This study combines drone surveys and geological data to construct a comprehensive three-dimensional model of bedding slopes. Utilizing FLAC3D and PFC2D models, derived from laboratory experiments, it simulates stress, deformation, and failure dynamics of slopes under various mining sequences. Incorporating fractal dimension analysis, the research evaluates the stability of slopes in relation to different mining sequences. The findings reveal that mining in an upslope direction minimizes disruption to overlying strata. Initiating extraction from lower segments increases tensile-shear stress in coal pillar overburdens, resulting in greater creep deformation towards the downslope than when starting from upper segments, potentially leading to localized landslides and widespread creep deformation in mined-out areas. The downslope upward mining sequence exhibits the least fractal dimensions, indicating minimal disturbance to both strata and surface. While all five mining scenarios maintain good slope stability under normal conditions, recalibrated stability assessments based on fractal dimensions suggest that downslope upward mining offers the highest stability under rainfall, contrasting with the lower stability and potential instability risks of upslope downward mining. These insights are pivotal for mining operations and geological hazard mitigation in multi-seam coal exploitation on bedding slopes.

关键词： Bedding rock landslides Mining-induced deformation Bedding slope stability Underground mining sequences Fractal-based strength reduction method

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Investigation of the block toppling evolution of a layered model slope by centrifuge test and discrete element modeling

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第1期16卷 112-122页

作者： Leilei Jin Hongkai Dong Fei Ye Yufeng Wei Jianfeng Liu Changkui Wang state key laboratory of Hydraulic and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu610065China state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu610059China

Primary toppling usually occurs in layered rock slopes with large anti-dip *** this paper,the block toppling evolution was explored using a large-scale centrifuge *** block column in the layered model slope was made of cement *** artificial cracks perpendicular to the block column were *** gages,displacement gages,and high-speed camera measurements were employed to monitor the deformation and failure processes of the model *** centrifuge test results show that the block toppling evolution can be divided into seven stages,*** compression,formation of major tensile crack,reverse bending of the block column,closure of major tensile crack,strong bending of the block column,formation of failure zone,and complete *** toppling is characterized by sudden large deformation and occurs in *** wedge-shaped cracks in the model incline towards the *** observations show that block toppling is mainly caused by bending failure rather than by shear *** tensile strength also plays a key factor in the evolution of block *** simulation results from discrete element method(DEM)is in line with the testing *** stress exists at the backside of rock column during toppling *** concentration results in the fragmented rock column and its degree is the most significant at the slope toe.

关键词： Block toppling Centrifuge Anti-dip slope Failure mechanism Discrete element method

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Atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction

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Nuclear Science and Techniques 2024年第3期35卷 40-52页

作者： Ding-Han Zhu Xiong Zhang Xiao-Qiang Li Peng Li Yan-Bin Wang Shuang Zhang state key laboratory of NBC protection for Civilian Beijing 102205China

In high-altitude nuclear detonations,the proportion of pulsed X-ray energy can exceed 70%,making it a specific monitoring signal for such *** pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric *** quantitatively analyze the effects of different satellite detection altitudes,burst heights,and transmission angles on the physical processes of X-ray transport and energy fluence,we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering *** proposed method is an improvement over the traditional analytical method that only computes direct-transmission *** traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo *** improved method reduces this error to within 10% under the same conditions,even reaching 1% in certain ***,its computation time is 48,000 times faster than that of the Monte Carlo *** results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors,inverting nuclear detonation source terms,and assessing ionospheric effects.

关键词： High-altitude nuclear detonation Atmospheric transmission Pulsed X-rays Scattering correction Analytical method Monte Carlo method

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Fourth-order phase-field modeling for brittle fracture in piezoelectric materials

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 837-856页

作者： Yu TAN Fan PENG Chang LIU Daiming PENG Xiangyu LI state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu 610059China College of Science Chang'an UniversityXi'an 710064China Applied Mechanics and Structure Safety key laboratory of Sichuan Province School of Mechanics and Aerospace EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Failure analyses of piezoelectric structures and devices are of engineering and scientific *** this paper,a fourth-order phase-field fracture model for piezoelectric solids is developed based on the Hamilton *** typical electric boundary conditions are involved in the present model to characterize the fracture behaviors in various physical situations.A staggered algorithm is used to simulate the crack *** polynomial splines over hierarchical T-meshes(PHT-splines)are adopted as the basis function,which owns the *** numerical simulations are performed to study the influence of the electric boundary conditions and the applied electric field on the fracture behaviors of piezoelectric *** electric boundary conditions may influence crack paths and fracture loads *** present research may be helpful for the reliability evaluation of the piezoelectric structure in the future applications.

关键词： isogeometric analysis(IGA) brittle fracture fourth-order phase-field model piezoelectric solid

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Empirical model of concrete block fragment behavior under explosion loads

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Science China Technological Sciences 2024年第8期67卷 2515-2529页

作者： YANG Shuai NING JianGuo REN HuiLan XU XiangZhao state key laboratory of Explosion Science and Safety protection Beijing Institute of Technology

Concrete structures undergo integral fragmentation under explosion loads. The fragmentation degree and particle-size distribution of concrete blocks under explosion loads must be considered during mining to ensure safety. In this study, the impulse is calculated based on the relationship between overpressure and time, and the impact energy of the explosion wave is obtained based on blast theory. Subsequently, the Mohr-Coulomb shear strength fracture criterion is introduced to determine the ultimate shear stress of the concrete materials, and an empirical model that can effectively calculate the energy consumption of concrete blocks under explosion loads is established. Furthermore, concrete fragments with different particle sizes under explosion scenarios are quantitatively predicted with the principle of energy conservation. Finally, explosion tests with different top standoff distances are conducted, and the concrete fragments after the explosion tests are recovered, sieved, weighed, and counted to obtain experimental data. The effectiveness of the fragment empirical model is verified by comparing the model calculation results with the experimental data. The proposed model can be used as a reference for civil blasting, protective engineering design, and explosion-damage assessment.

关键词： concrete structures explosion loads fragment behavior empirical model

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The risk factors and threshold level of subchronic inhalation exposure of reclaimed water

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Journal of Environmental Sciences 2024年第3期137卷 639-650页

作者： Jiayang Kong Yun Lu Yunru Ren Menghao Chen Gang Liu Liangliang Shi state key Joint laboratory of Environment Simulation and Pollution Control State Environment Protection Key Laboratory of Microorganism Application and Risk ControlSchool of EnvironmentTsinghua UniversityBeijing 100084China

Inhalation of reclaimed water is known to cause lung infammation,and free endotoxins have been shown to be a major risk factor for acute *** exposure has also been shown to induce infammatory responses with visible tissue ***,subchronic risk factors have yet to be identified,and a threshold for the protection of occupational populations during urban reuse is *** this study,potential risk factors in reclaimed water were examined by subchronic exposure with fractionated reclaimed water,and the health risk threshold was tested with a series of diluted reclaimed ***,following a 12-week exposure,macromolecules and microorganisms were found to be two major risk factors in reclaimed water that could cause pulmonary infammation,including increased proportion of polymorphonuclear leukocytes in bronchoalveolar fuid,formation of inducible bronchus-associated lymphoid tissue,and elevation of Immunoglobulin A ***,infammation persisted after a 4-week recovery *** calculated threshold of reclaimed water exposure for mice was 31.8 Endotoxin Unit(EU)/(kg·day)under when exposed to 50%additional relative humidity from reclaimed water at 25℃ for 2 hr/***,the subchronic threshold estimate for humans under the same exposure conditions was found to be 12.2 EU/(kg·day),corresponding to endotoxin levels of 61.7 EU/mL in reclaimed *** threshold level of endotoxin was lower than that in most non-potable reclaimed *** findings of this study suggest that occupational exposure of reclaimed water can serve as a potential risk to workers.

关键词： Reclaimed water Inhalation exposure Risk factor Threshold Infammation Endotoxin

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Integrated wellbore-reservoir-geomechanics modeling for enhanced interpretation of distributed fiber-optic strain sensing data in hydraulicfracture analysis

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3136-3148页

作者： Lijun Liu Xinglin Guo Xiaoguang Wang state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu610059China Tianfu Yongxing laboratory Chengdu610213China College of Energy Chengdu University of TechnologyChengdu610059China state key laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu610059China

Fiber-optic distributed strain sensing(FO-DSS)has been successful in monitoring strain changes along horizontal wellbores in hydraulically fractured ***,the mechanism driving the various FO-DSS responses associated with near-wellbore hydraulic fracture properties is still *** address this knowledge gap,we use coupled wellbore-reservoir-geomechanics simulations to study measured strain-change behavior and infer hydraulic fracture *** crossflow among fractures is captured through explicit modeling of the transient wellbore *** addition,local grid refinement is applied to accurately capture strain changes along the fiber.A Base Case model was designed with four fractures of varying properties,simulating strain change signals when the production well is shut-in for 10 d after 240 d of production and reopened for 2 ***-pressure plots for different fracture clusters were used to gain insights into inferring fracture properties using DSS *** comparing the model with and without the wellbore,distinct strain change signals were observed,emphasizing the importance of incorporating the wellbore in FO-DSS *** effects of fracture spacing and matrix permeability on strain change signals were thoroughly *** results of our numerical study can improve the understanding of the relation between DSS signals and fracture hydraulic properties,thus maximizing the value of the dataset for fracture diagnostics and characterization.

关键词： Distributed strain sensing Fracture diagnostic Coupled flow and geomechanics Transient wellbore flow

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Large-scale toppling slope under water level fluctuation of reservoir:A case of Yunnan Province,China

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第8期16卷 3034-3046页

作者： Leilei Jin Yufeng Wei Fei Ye Wenxi Fu Jianfeng Liu Shuwu Li state key laboratory of Hydraulic and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu610065China state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu610059China Northwest Engineering Corporation Limited Xi’an710065China

Landslides induced by reservoir inundation are common in Southwest China,negatively influencing hydropower *** hydropower station dam was constructed in the upper reaches of the Lancang River,accordingly causing the water level at the Lajinshengu slope to increase by 30 m.A tension crack with a visible depth of 8 m was observed in the upper sector of the Lajinshengu slope after reservoir impoundment for 170 *** the following days,numerous cracks appeared on the surface of the slope,and the maximum displacement of the slope reached 3.22 ***,a large-scale active deformation body within the Lajinshengu slope formed with an area of 2.62×10^(5)m^(2)and a volume of 1.65×10^(7)m^(3).Detailed field investigations,on-site monitoring,and centrifugal model tests were carried out to analyze the surface features,deformation characteristics,and failure mechanism of the Lajinshengu *** results show that the slope is an ancient landslide,divided into two parts(*** A and zone B)by the *** B is a traction landslide caused by the displacement of zone *** longterm inundation weakens the soft rock at the slope foot,intensifying the toppling of bedrock and consequently triggering the sliding of the overburden in zone *** failure mode of the Lajinshengu slope is a typical case of toppling-sliding failure,and the underlying rock toppling drives the overlying *** addition,early identification methods for toppling deformation covered by overburdened soil were proposed based on monitoring data and deformation signs.

关键词： Lajinshengu slope Reservoir impoundment Early identification Failure mechanism Toppling-sliding slope failure mode

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A process-oriented approach for identifying potential landslides considering time-dependent behaviors beyond geomorphological features

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第3期16卷 961-978页

作者： Xiang Sun Guoqing Chen Xing Yang Zhengxuan Xu Jingxi Yang Zhiheng Lin Yunpeng Liu state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu610059China China Railway Eryuan Engineering Group Co.Ltd. Chengdu610031China Power China Chengdu Engineering Co.Ltd. Chengdu610072China

Geomorphological features are commonly used to identify potential ***,overemphasis on these features could lead to *** research proposes a process-oriented approach for potential landslide identification that considers time-dependent *** method integrates comprehensive remote sensing and geological analysis to qualitatively assess slope stability,and employs numerical analysis to quantitatively calculate aging ***,a time-dependent stability calculation method for anticlinal slopes is developed and implemented in discrete element software,incorporating time-dependent mechanical and strength reduction *** considering the time-dependent evolution of slopes,this method highlights the importance of both geomorphological features and time-dependent behaviors in landslide *** method has been applied to the Jiarishan slope(JRS)on the Qinghai-Tibet Plateau as a case *** results show that the JRS,despite having landslide geomorphology,is a stable slope,highlighting the risk of misjudgment when relying solely on geomorphological *** work provides insights into the geomorphological characterization and evolution history of the JRS and offers valuable guidance for studying slopes with similar landslide ***,the process-oriented method incorporating timedependent evolution provides a means to evaluate potential landslides,reducing misjudgment due to excessive reliance on geomorphological features.

关键词： Geomorphological features Evolution history Time-dependent stability calculation Landslides identification Qinghai-Tibet Plateau

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Advances in ice avalanches on the Tibetan Plateau

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Journal of Mountain Science 2024年第6期21卷 1814-1829页

作者： TANG Minggao LI Guang ZHAO Huanle XU Qiang WU Guangjian YANG Wei GUO Daojing state key laboratory of Geohazard Prevention and geoenvironment protection Chengdu University of TechnologyChengdu 610059China College of Environment and Civil Engineering Chengdu University of TechnologyChengdu 610059China Institute of Tibetan Plateau Research Chinese Academy of SciencesBeijing 100101China

As some of the greatest natural disasters in the cryosphere,ice avalanches(IAs)seriously threaten lives and cause catastrophic damage to the resource environment,but a comprehensive overview of the state of knowledge on IAs remains *** summarized 63 IAs on the Tibetan Plateau(TP)since the 20th century,of which,over 20 IAs occurred after the 21st *** distributions of IAs are mainly concentrated in the southeastern and northwestern TP,and the occurrence time of IAs is mostly concentrated from July to *** highlight recent advances in mechanical properties and genetic mechanisms of IAs and emphasize that temperature,rainfall,and seismicity are the inducing *** failure modes of IAs are summarized into 6 categories by examples:slip pulling type,slip toppling type,slip breaking type,water level collapse type,cave roof collapse type,and wedge failure ***,we deliver recommendations concerning the risk assessment and prediction of *** results provide important scientific value for addressing climate change and resisting glacier-related hazards.

关键词： Ice avalanche Global warming Genetic mechanism Risk assessment Tibetan Plateau

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