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performances of fissured red sandstone after thermal treatment with constant-amplitude and low-cycle impacts

Journal of Rock Mechanics and geotechnical Engineering 2024年第2期16卷 561-587页

作者： Yongjun Chen Tubing Yin p.g.ranjith Xibing Li Qiang Li Dengdeng Zhuang School of Resources and Safety Engineering Central South UniversityChangsha410083China Department of Civil Engineering Monash UniversityMelbourne3800Australia Oulu Mining School University of OuluOuluFI-90014Finland

In the engineering practices,it is increasingly common to encounter fractured rocks perturbed by temperatures and frequent dynamic *** this paper,the dynamic behaviors and fracture characteristics of red sandstone considering temperatures(25℃,200℃,400℃,600℃,and 800℃)and fissure angles(0°,30°,60°,and 90°)were evaluated under constant-amplitude and low-cycle(CALC)impacts actuated by a modified split Hopkinson pressure bar(SHpB)***,fracture morphology and second-order statistics within the grey-level co-occurrence matrix(gLCM)were examined using scanning electron microscopy(SEM).Meanwhile,the deep analysis and discussion of the mechanical response were conducted through the synchronous thermal analyzer(STA)test,numerical simulations,one-dimensional stress wave theory,and material *** multiple regression models between response variables and interactive effects of independent variables were established using the response surface method(RSM).The results demonstrate the fatigue strength and life diminish as temperatures rise and increase with increasing fissure angles,while the strain rate exhibits an inverse ***,the peak stress intensification and strain rate softening observed during CALC impact exhibit greater prominence at increased fissure *** failure is dominated by tensile damage with concise evolution paths and intergranular cracks as well as the compressor-crushed zone which may affect the failure mode after 400℃.The second-order statistics of gLCM in SEM images exhibit a considerable dependence on the ***,thermal damage dominated by thermal properties controls the material structure and wave impedance and eventually affects the incident wave *** tensile wave reflected from the fissure surface is the inherent mechanism responsible for the angle effect exhibited by the fatigue strength and ***,the peak stress intensification and strain rate softening during impact are determ

关键词： Red sandstone Temperature Fissure Constant-amplitude and low-cycle(CALC) impact Fatigue failure Response surface method(RSM)

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Experimental study on the influence of hydrostatic stress on the Lode angle effect of porous rock

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International Journal of Mining Science and Technology 2022年第4期32卷 727-735页

作者： Zhenlong Song Zhenguo Zhang p.g.ranjith Wanchun Zhao Chao Liu Department of Earth and Space Sciences Southern University of Science and TechnologyShenzhenGuangdong 518055China State Key Laboratory of Coalmine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China Deep Earth Energy Research Laboratory Department of Civil EngineeringMonash UniversityMelbourneVictoria 3800Australia School of Earth and Space Sciences University of Science and Technology of ChinaHefei 230026China School of Electrical Engineering&Information Northeast Petroleum UniversityDaqing 163318China

To investigate the deformation mechanisms of rock under hydrostatic stress, destructive experiments were conducted on sandstone under different levels of hydrostatic stress and stress Lode angles. The results reveal that the shape of the strength envelope on the π plane gradually changes from the shape of the Lade criterion to the shape of the Drucker-prage criterion with an increase in hydrostatic ***, there exists a deviation between the strain and stress paths for porous rocks on the π plane,and the deviation decreases with an increase in stress Lode angle and hydrostatic stress. A rock failure hypothesis based on the rock porous structure was proposed to investigate the reasons for the abovementioned phenomena. It was found that the shear expansion in the minimum principal stress direction is the dominant factor affecting the Lode angle effect(LAE);the magnitude of the hydrostatic stress induces the variation of the porous structure and influences the shear expansion. Therefore, the hydrostatic stress state affects the LAE. The failure hypothesis proposed in this paper can clarify the hydrostatic stress effect, LAE, and the variation of the rock strength envelope shape.

关键词： Lode angle effect Hydrostatic stress effect Strength envelope curve porous structure

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Experimental investigations on effects of gas pressure on mechanical behaviors and failure characteristic of coals

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Journal of Rock Mechanics and geotechnical Engineering 2023年第2期15卷 412-428页

作者： Yi Xue p.g.ranjith Feng gao Zhizhen Zhang Songhe Wang State Key Laboratory of Eco-hydraulics in Northwest Arid Region Xi’an University of TechnologyXi’an710048China Deep Earth Energy Laboratory Department of Civil EngineeringMonash UniversityBuilding 60MelbourneVictoria3800Australia State Key Laboratory for geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221006China

The mechanical behavior of coal is the key factor affecting underground coal mining and coalbed methane *** this study,triaxial compression and seepage tests were carried out on coal at different gas *** mechanical properties and failure process of coal were studied,as well as the acoustic emission(AE)and strain *** influence of gas pressure on the mechanical parameters of this coal was *** on the conventional energy calculation formula,the pore pressure was introduced through the effective stress formula,and each energy component of coal containing gas was refined *** contribution of gas pressure to the total energy input and dissipation during loading was quantitatively ***,the influence of gas pressure on coal strength was theo-retically analyzed from the perspectives of MohreCoulomb criterion and fracture *** results show that the total absorbed energy comprises the absorbed energy in the axial pressure direction(positive)and in the confining pressure direction(negative),as well as that induced by the pore pressure(initially negative and then positive).The absorbed energy in the axial pressure direction accounts for the main proportion of the total energy absorbed by *** quiet period of AE in the initial stage shortens,and AE activity increases during the pre-peak stage under high gas *** fractal characteristics of AE in three stages are studied using the correlation *** AE process has different forms of self-similarity in various deformation stages.

关键词： Coal gas pressure Acoustic emission(AE) Strain energy Fractal characteristics

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Direct Evidence of Coal Swelling and Shrinkage with Injecting CO_(2) and N_(2) Using in-situ Synchrotron X-ray Microtomography

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Engineering 2022年第11期18卷 88-95页

作者： guanglei Zhang p.g.ranjith Herbert E.Huppert Department of Earth Science and Engineering Imperial College LondonLondon SW72BPUK Deep Earth Energy Laboratory Department of Civil EngineeringMonash UniversityMelbourneVIC3800Australia Institute of Theoretical geophysics King’s CollegeCambridge CB21STUK

Deep coal seams are one of the world’s most widespread deposits for carbon dioxide(C02)disposal and are generally located near large point sources of CO_(2)*** injection of CO_(2)into coal seams has great potential to sequester CO_(2)while simultaneously enhancing coalbed methane(CO_(2)-ECBM)*** tests of CO_(2)-ECBM have been conducted in coal seams worldwide with favorable early ***,one of the main technical barriers in coal seams needs to be resolved:Injecting CO_(2)reduces coal permeability and well ***,using in situ synchrotron X-ray microtomography,we provide the first observational evidence that injecting nitrogen(N_(2))can reverse much of this lost permeability by reopening fractures that have closed due to coal swelling induced by CO_(2)*** findings support the notion that injecting minimally treated flue gas-a mixture of mainly N_(2) and CO_(2)-is an attractive alternative for ECBM recovery instead of pure CO_(2)injection in deep coal ***,flue gas produced by power plants could be directly injected after particulate removal,thus avoiding high CO_(2)-separation ***,the presence of N_(2)makes it possible to maintain a sufficiently high level of coal *** results suggest that flue-gas ECBM for deep coal seams may provide a promising path toward net-zero emissions from coal mines.

关键词： CCS CO_(2)-ECBM Carbon neutrality X-ray imaging Coal permeability

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Evaluation on the anisotropic brittleness index of shale rock using geophysical logging

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petroleum 2023年第4期9卷 545-557页

作者： Junchuan gui Jianchun guo Yu Sang Yaxi Chen Tianshou Ma p.g.ranjith Research Institute of Shale gas PetroChina Southwest Oil and Gasfield CompanyChengdu610051China State Key Laboratory of Oil and gas Reservoir geology and Exploitation Southwest Petroleum UniversityChengdu610500China Shunan gas Mine PetroChina Southwest Oil and Gas Field CompanyLuzhou646000China Downhole Service Company CNPC Chuanqing Drilling Engineering Company LimitedChengdu610501China Deep Earth Energy Laboratory Department of Civil EngineeringMonash UniversityMelbourne3800Australia

The brittleness index plays a significant role in the hydraulic fracturing design and wellbore stability analysis of shale *** brittleness indices have been proposed to characterize the brittleness of shale rocks,but almost all of them ignored the anisotropy of the brittleness ***,uniaxial compression testing integrated with geophysical logging was used to provide insights into the anisotropy of the brittleness index for Longmaxi shale,the presented method was utilized to assess brittleness index of Longmaxi shale formation for the interval of 3155e3175 m in CW-1 *** results indicated that the brittleness index of Longmaxi shale showed a distinct anisotropy,and it achieved the minimum value at β=45°-60°.As the bedding angle increased,the observed brittleness index(BI_(2_β))decreased firstly and increased then,it achieved the lowest value at β=40°-60°,and it is consistent with the uniaxial compression testing *** to the isotropic brittleness index(β=0°),the deviation of the anisotropic brittleness index ranged from 10%to 66.7%,in other words,the anisotropy of brittleness index cannot be ignored for Longmaxi *** matter content is one of the main intrinsic causes of shale anisotropy,and the anisotropy degree of the brittleness index generally increases with the increase in organic matter *** present work is valuable for the assessment of anisotropic brittleness for hydraulic fracturing design and wellbore stability analysis.

关键词： Shale rock Brittleness Brittleness index Anisotropy Transverse isotropy geophysical logging

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Discrete element modeling on the crack evolution behavior of brittle sandstone containing three fissures under uniaxial compression

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Acta Mechanica Sinica 2015年第6期31卷 871-889页

作者： Sheng-Qi Yang Yan-Hua Huang p.g.ranjith Yu-Yong Jiao Jian Ji State Key Laboratory for geomechanics and Deep Underground Engineering School of Mechanics and Civil Engineering China University of Mining and Technology Deep Earth Energy Research Laboratory Department of Civil Engineering Monash University Institute of Rock and Soil Mechanics Chinese Academy of Sciences

Based on experimental restilts of brittle, intact sandstone under uniaxial compression, the micro-parameters were firstly confirmed by adopting particle flow code （pFC2D）. Then, the validation of the simulated models were cross checked with the experimental results of brittle sandstone containing three parallel fissures under uniaxial compression. The simulated results agreed very well with the experimental results, including the peak strength, peak axial strain, and ultimate failure mode. Using the same micro- parameters, the numerical models containing a new geometry of three fissures are constructed to investigate the fissure angle on the fracture mechanical behavior of brittle sandstone under uniaxial compression. The strength and deformation parameters of brittle sandstone containing new three fissures are dependent to the fissure angle. With the increase of the fis- sure angle, the elastic modulus, the crack damage threshold, and the peak strength of brittle sandstone containing three fissures firstly increase and secondly decrease. But the peak axial strain is nonlinearly related to the fissure angle. In the entire process of deformation, the crack initiation and propagation behavior of brittle sandstone containing three fissures under uniaxial compression are investigated with respect to the fissure angle. Six different crack coalescence modes are identified for brittle sandstone containing three fissures under uniaxial compression. The influence of the fissure angle on the length of crack propagation and crack coalescence stress is evaluated. These investigated conclusions are very important for ensuring the stability and safety of rock engineering with intermittent structures.

关键词： Brittle sandstone ·pFC2D Three fissures ·Crack initiation Crack propagation Crack coalescence

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Crushing and embedment of proppant packs under cyclic loading: An insight to enhanced unconventional oil/gas recovery

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geoscience Frontiers 2021年第6期12卷 376-393页

作者： K.M.A.S.Bandara p.g.ranjith T.D.Rathnaweera W.A.M.Wanniarachchi S.Q.Yang Department of Civil Engineering Monash UniversityBuilding 60MelbourneVictoria3800Australia State Key Laboratory for geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou 221116China

Crushing and embedment are two critical downhole proppant degradation mechanisms that lead to a significant drop in production outputs in unconventional oil/gas stimulation projects. These persistent production drops due to the non-linear responses of proppants under reservoir conditions put the future utilization of such advanced stimulation techniques in unconventional energy extraction in doubt. The aim of this study is to address these issues by conducting a comprehensive experimental approach. According to the results, whatever the type of proppant, all proppant packs tend to undergo significant plastic deformation under the first loading ***, the utilization of ceramic proppants(which retain proppant pack porosity up to 75%), larger proppant sizes(which retain proppant pack porosity up to 15.2%) and higher proppant concentrations(which retain proppant pack porosity up to 29.5%) in the fracturing stimulations with higher in-situ stresses are recommended to de-escalate the critical consequences of crushing associated issues. Similarly, the selection of resin-coated proppants over ceramic and sand proppants may benefit in terms of obtaining reduced proppant *** addition, selection of smaller proppant sizes and higher proppant concentrations are suggested for stimulation projects at depth with sedimentary formations and lower in-situ stresses where proppant embedment predominates. Furthermore, correlation between proppant embedment with repetitive loading cycles was ***, microstructural analysis of the proppant-embedded siltstone rock samples revealed that the initiation of secondary induced fractures. Finally, the findings of this study can greatly contribute to accurately select optimum proppant properties(proppant type, size and concentration) depending on the oil/gas reservoir characteristics to minimize proppant crushing and embedment effects.

关键词： proppant Micro-CT analysis proppant crushing proppant embedment Secondary induced fractures Cyclic loading

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Three-dimensional failure behavior and cracking mechanism of rectangular solid sandstone containing a single fissure under triaxial compression

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Rock Mechanics Bulletin 2022年第1期1卷 126-148页

作者： Sheng-Qi Yang Wen-Ling Tian p.g.ranjith Xiang-Ru Liu Miao Chen Wu Cai State Key Laboratory for geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116PR China Deep Earth Energy Research Laboratory Department of Civil EngineeringMonash UniversityMelbourneVictoria3800Australia College of Energy and Mining Engineering Shandong University of Science and TechnologyQingdao266590PR China School of Mines China University of Mining and TechnologyXuzhou221116PR China

In actual rock engineering,fissures play an important role in determining the mechanical parameters of rock mass,whereas it is very difficult to construct fissures in cylindrical ***,the pre-fissured rectangular rock specimens were constructed ***,a series of triaxial compression experimental results on the failure mechanical behavior of rectangular solid sandstone specimens containing a single fissure were *** lateral strain in different directions was monitored and the experimental results show that elastic modulus and axial strain increase non-linearly with confining pressure,and the average poisson’s ratio parallel to fissure(μ2)is larger than that vertical to fissure(μ3).The cohesion,Hoek-Brown parameters of peak strength show similar trends with that of crack damage threshold to the fissure angle(α),and the parameters of the peak strength are larger than those of crack damage ***,the internal friction angles of the peak strength and crack damage threshold are almost *** on the geometries and properties of cracks,ten typical crack types are *** vertical to pre-existing fissures occur in specimens under uniaxial compression,whereas cracks parallel to pre-existing fissures occur under triaxial ***,X-ray micro-computed tomography(CT)observations are conducted to analyze the internal damage mechanism of sandstone specimens with respect to various fissure *** 3-D CT images indicate obvious effects of confining pressure and fissure angle on the crack system of sandstone *** research elucidates the fundamental nature of rock failure under triaxial compression.

关键词： Rectangular solid sandstone Single fissure Triaxial deformation peak strength Damage behavior X-ray micro-CT

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Bibliometric analysis of research challenges and trends in urban underground space

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Deep Underground Science and Engineering 2024年第2期3卷 207-215页

作者： You Zhang Liang Zheng Lingling He Yuyong Jiao Hanfa peng ranjith pgamage Faculty of Engineering China University of GeosciencesWuhanChina Department of Civil Engineering Monash UniversityClaytonVictoriaAustralia Sinohydro Engineering Bureau Co. LtdPower ChinaXiningChina 4Wuhan Geomatic InstituteWuhanChina

The utilization and development of urban underground space play a crucial role in optimizing the layout of civic architecture and enhancing the urban ecological environment,which contributes toward increasing the overall carrying capacity and promoting sustainable development in *** delve into the research progress of urban underground space,knowledge maps were created using the information visualization software *** literature was systematically extracted from three prominent databases,namely,Web of Science,Scopus,and China National Knowledge *** to the bibliometric analysis of the co-citation and core words co-occurrence,the trends and challenges of research on urban underground space were *** highlighted by the results obtained,it still remains highly challenging to achieve interdisciplinary collaboration in urban underground space research;the research trends of urban underground space consist of collaborative planning and whole life cycle sustainable development,multisource geological data informatization and resource evaluation,infrastructure design optimization,and intelligent *** knowledge map,drawn using bibliometric methods,offers a quantitative analysis of literature retrieval across various *** is recognized as an essential tool for exploring and identifying challenges and trends in urban underground space.

关键词： bibliometric analysis knowledge groups urban underground space VOSviewer

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NIR-switchable local hydrogen generation by tandem bimetallic MOFs nanocomposites for enhanced chemodynamic therapy

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Regenerative Biomaterials 2024年第1期3卷 58-68页

作者： Jun Zhong Xiang Zheng Yuan Wen Yuewei Li Jianting Zhang ranjith Kumar Kankala Shibin Wang Aizheng Chen Institute of Biomaterials and Tissue Engineering Huaqiao UniversityXiamen 361021China Fujian provincial Key Laboratory of Biochemical Technology Huaqiao UniversityXiamen 361021China Fujian provincial Key Laboratory of Biomass Low-Carbon Conversion Huaqiao UniversityXiamen 361021China

The inadequate quantity of hydrogen peroxide(H_(2)O_(2))in cancer cells promptly results in the constrained success of chemodynamic therapy(CDT).Significant efforts made throughout the years;nevertheless,researchers are still facing the great challenge of designing a CDT agent and securing H_(2)O_(2) supply within the tumor *** this study,taking advantage of H_(2)O_(2) level maintenance mechanism in cancer cells,a nanozyme-based bimetallic metal-organic frameworks(MOFs)tandem reactor is fabricated to elevate intracellular H_(2)O_(2) levels,thereby enhancing *** addition,under nearinfrared excitation,the upconversion nanoparticles(UCNps)loaded into the MOFs can perform photocatalysis and generate hydrogen,which increases cellular susceptibility to radicals induced from H_(2)O_(2),inhibits cancer cell energy,causes DNA damages and induces tumor cell apoptosis,thus improving CDT therapeutic efficacy *** proposed nanozyme-based bimetallic MOFs-mediated CDT and UCNps-mediated hydrogen therapy act as combined therapy with high efficacy and low toxicity.

关键词： chemodynamic therapy nanozyme bimetallic MOFs gas therapy

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