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Numerical evaluation of strength and deformability of fractured rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2013年第6期5卷 419-430页

作者： Majid Noorian Bidgoli zhihong zhao Lanru Jing Department of Land and Water Resources Engineering Engineering Geology and Geophysics Research GroupRoyal Institute of Technology (KTH) Department of Geological Sciences Stockholm University

Knowledge of the strength and deformability of fractured rocks is important for design, construction and stability evaluation of slopes, foundations and underground excavations in civil and mining engineering. However, laboratory tests of intact rock samples cannot provide information about the strength and deformation behaviors of fractured rock masses that include many fractures of varying sizes, orientations and locations. On the other hand, large-scale in situ tests of fractured rock masses are economically costly and often not practical in reality at present. Therefore, numerical modeling becomes necessary. Numerical predicting using discrete element methods(DEM) is a suitable approach for such modeling because of their advantages of explicit representations of both fractures system geometry and their constitutive behaviors of fractures, besides that of intact rock matrix. In this study, to generically determine the compressive strength of fractured rock masses, a series of numerical experiments were performed on two-dimensional discrete fracture network models based on the realistic geometrical and mechanical data of fracture systems from feld mapping. We used the UDEC code and a numerical servo-controlled program for controlling the progressive compressive loading process to avoid sudden violent failure of the models. The two loading conditions applied are similar to the standard laboratory testing for intact rock samples in order to check possible differences caused by such loading conditions. Numerical results show that the strength of fractured rocks increases with the increasing confning pressure, and that deformation behavior of fractured rocks follows elasto-plastic model with a trend of strain hardening. The stresses and strains obtained from these numerical experiments were used to ft the well-known Mohr-Coulomb(MC) and Hoek-Brown(H-B) failure criteria, represented by equivalent material properties defning these two criteria. The results show that bot

关键词： Strength Deformability Fractured rocks Discrete element methods(DEM) Failure criteria

Bio-inspired superhydrophobic magnesium alloy surfaces with active anti-corrosion and self-healing properties

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Nano Research 2023年第2期16卷 3312-3319页

作者： Qiang Li Xudong Zhang Shuang Ben zhihong zhao Yuzhen Ning Kesong Liu Lei Jiang Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology School of Chemistry Beihang UniversityBeijing 100191China School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China

Bio-inspired superhydrophobic magnesium(Mg)alloy surfaces are of increasing interest in corrosion protection due to superior barrier and shielding ***,superhydrophobic(SHB)anti-corrosion surfaces are susceptible to damage,which limit their extensive *** this end,a micro/nano structure-functional molecule SHB composite coating with self-healing and active anti-corrosion dual-function properties was designed on Mg alloys *** dual-function SHB composite anti-corrosion coating based on lauric acid(La)intercalated and modified hydrotalcite(La-LDH)consisted of three-layer structure,namely La-LDH powder/polydimethylsiloxane(PDMS)/La-LDH *** anti-corrosion performance of as-prepared coatings was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The results indicate that the SHB coating shows excellent active corrosion ***,we also examined the self-healing and anti-corrosion properties of SHB coating upon physical damage and explained the healing *** heat treatment,the damaged SHB coating regain its surface microstructure and corrosion protection *** work expands new insights for the wide application of Mg alloys and the research in the field of metal protection.

关键词： magnesium alloys anti-corrosion coating superhydrophobic self-healing active anti-corrosion property

Unloading-induced permeability recovery in rock fractures

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第12期15卷 3148-3162页

作者： Tao Lin Wen Meng Yuedu Chen zhihong zhao Bing Liu Jintong Zhang Sicong Chen Xingguang zhao Department of Civil Engineering Tsinghua UniversityBeijingChina Key Laboratory of Neotectonic Movement and Geohazard Institute of GeomechanicsChinese Academy of Geological SciencesBeijingChina College of Mining Engineering Taiyuan University of TechnologyTaiyuanChina CNNC Key Laboratory on Geological Disposal of High-level Radioactive Waste Beijing Research Institute of Uranium GeologyBeijingChina

Underground space creation and energy extraction, which induce unloading on rock fractures, commonly occur in various rock engineering projects, and rock engineering projects are subjected to high temperatures with increasing depth. Fluid flow behavior of rock fractures is a critical issue in many subsurface rock engineering projects. Previous studies have extensively considered permeability evolution in rock fractures under loading phase, whereas changes in fracture permeability under unloading phase have not been fully understood. To examine the unloading-induced changes in fracture permeability under different temperatures, we performed water flow-through tests on fractured rock samples subjected to decreasing confining pressures and different temperatures. The experimental results show that the permeability of fracture increases with unloading of confining pressure but decreases with loading-unloading cycles. Temperature may affect fracture permeability when it is higher than a certain threshold. An empirical model of fracture hydraulic aperture including two material parameters of initial normal stiffness and maximum normal closure can well describe the permeability changes in rough rock fracture subjected to loading-unloading cycles and heating. A coupled thermo-mechanical model considering asperity damage is finally used to understand the influences of stress paths and temperatures on fracture permeability.

关键词： Unloading Permeability Rock fracture Temperature Empirical model

Convenient Synthesis of 1-Thiohydroxypyrene by Newman-Kwart Rearrangement

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Chemical Research in Chinese Universities 2015年第2期31卷 224-227页

作者： ZHANG Ran XU Lihua CHEN Hui QIN zhihong zhao Yu Ni Zhonghai School of Chemical Engineering and Technology China University of Mining and Technology Xuzhou 221116 P. R. China

l-Thiohydroxypyrene（l） and its two intermediates, l-pyrenyl-O-thiocarbamate（2） and l-pyrenyl-S-thiocarbamate（3）, were synthesized using l-hydroxypyrene as the starting material. The key synthetic step is New- manoKwart rearrangement. The results indicate that the Newman-Kwart rearrangement is more effective in suitable solvent than conventional method based on pure organic compound. The structures of compounds 1-3 were characterized by FTIR, NMR, CJC-MS and elementary analysis. The crystal structures of two new compounds（2 and 3） were determined by single crystal X-ray diffraction analysis. The whole synthetic process is simple, mild and with high yield.

关键词： Newman-Kwart rearrangement l-Thiohydroxypyrene Crystal structure

A bioinspired magnetic responsive cilia array surface for microspheres underwater directional transport

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Science China Chemistry 2020年第3期63卷 347-353页

作者： Shuang Ben Jinjia Yao Yuzhen Ning zhihong zhao Jinlong Zha Dongliang Tian Kesong Liu Lei Jiang Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology School of Chemistry Beihang UniversityBeijing 100191China Beijing Advanced Innovation Center for Biomedical Engineering Beihang UniversityBeijing 100191China

Bio-inspired surfaces are usually designed by imitating the surface properties of a particular biological species,or combing with the surface characteristics of multiple biological species to construct a cross-species ***,inspired by the structure and rhythmic swing of human pulmonary cilia,and the directional migration of pigeons by geomagnetic field,an integrated system of biomimetic hydrophobic magnetic cilia array surface with reversible deformation properties and excellent magnetic response performance for solid microspheres underwater transport is designed and *** by an external magnetic field,the magnetic responsive cilia array surface can directionally and continuously transport microspheres underwater in periodic *** work will shed new light on the designing of micromanipulation systems for micro-objects transport,and promote the practical application of micro-operating systems in underwater transportation and drug delivery.

关键词： cilia-inspired surface underwater microspheres transport magnetic response micro-operating system

An optimization model for conductivity of hydraulic fracture networks in the Longmaxi shale,Sichuan basin,Southwest China

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Energy Geoscience 2020年第1期1卷 47-54页

作者： zhihong zhao Kaidi Wu Yu Fan Jianchun Guo Bo Zeng Wenhan Yue State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChenduSichuanChina Shale Gas Research Institute PetroChina Southwest Oil and Gas Field CompanyChenduSichuanChina

Shale gas is an important unconventional *** economic recovery of shale gas is only possible when a fracture network with sufficient conductivity is created by hydraulic fracturing,that,if effectively propped,connects fracturing fractures and natural *** on the Longmaxi shale in the Sichuan Basin,Southwest China,we built an optimization model for conductivity of multi-grade fractures based on equivalent seepage *** then experimentally analyzed the conductivity of self-propped and sand-propped fractures,and optimized the propping patterns of multi-grade hydraulic fractures in shale gas *** concluded that the propping effectiveness of fracture networks could be improved by using low concentrations of small-sized sands and by focusing on creating a large number of self-propped *** applying this understanding to the optimization of fracturing designs for the Longmaxi shale,we successfully created networks of well-propped fractures.

关键词： Fracture network Conductivity optimization Propped fracture Self-propped fracture Shale gas

Improving actionable warning identification via the refined warning-inducing context representation

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Science China(Information Sciences) 2024年第5期67卷 321-322页

作者： Xiuting GE Chunrong FANG Xuanye LI Quanjun ZHANG Jia LIU zhihong zhao Zhenyu CHEN State Key Laboratory for Novel Software Technology Nanjing University

Static analysis tools(SATs) have shown potential ability in software quality assurance [1]. However, SATs report an overwhelming number of warnings, where most warnings are unactionable ones(i.e., warnings that are not acted on or fixed by developers). It is not a trivial task for developers to find actionable warnings(i.e., warnings that are acted on and fixed by developers) in all reported warnings. Hence,the excessive unactionable warnings seriously impede the usability of SATs [2].

关键词： representation identification context actionable improving inducing refined warning

Unidirectional movement behavior of underwater bubbles on the wettability gradient mesh via asymmetrical bounce

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Science China Chemistry 2024年第8期67卷 2606-2613页

作者： Yuzhen Ning zhihong zhao Shuang Ben Qiang Li Cunming Yu Xudong Zhang Huawei Chen Kesong Liu Lei Jiang School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology School of ChemistryBeihang UniversityBeijing 100191China Research Institute of Aero-Engine Beihang UniversityBeijing 100191China School of Materials Science and Engineering Shenyang Ligong UniversityShenyang 110159China Tianmushan Laboratory Hangzhou 310023China The Analysis Testing CenterBeihang UniversityBeijing 100191China

The impact of underwater bubbles on solid surfaces with a gradient wettability is important for fundamental science and technological applications. Despite progress in the translational motion of underwater bubbles on asymmetric surface, a fundamental dynamic understanding of asymmetrical bounce behavior of the underwater bubble needs to be further ***, we investigate asymmetrical bounce of underwater bubbles after impacting the wettability gradient copper mesh *** bounce of the underwater bubble on the wettability gradient mesh(WGM) surface is composed by asymmetrical spread in the spread process and asymmetrical recoil in the recoil process, which induce the unidirectional movement ***, effective bubble-size manipulation can be easily implemented due to different volumes of bubbles remaining at different locations of WGM surface. We envision that this work will provide a new understanding of asymmetrical bounce behavior of the underwater bubble on the wettability gradient surface, and propose a novel and feasible strategy for constructing the underwater bubble manipulation system.

关键词： asymmetrical bounce unidirectional movement behavior gradient wettability

Effect of fracture fluid flowback on shale microfractures using CT scanning

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 426-436页

作者： Jiale He zhihong zhao Yiran Geng Yuping Chen Jianchun Guo Cong Lu Shouyi Wang Xueliang Han Jun Zhang State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu610500China Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy and Power EngineeringXi’an Jiaotong UniversityXi’an710049China Drilling Test Engineering Department of Longdong Oil and Gas Development Company Changqing OilfieldPetroChina Company LimitedQingyang745000China Tight Oil and Gas Exploration and Development Project Department PetroChina Southwest Oil and Gas Field CompanyChengdu610056China No.11 Oil Production Plant Changqing Oilfield CompanyPetroChina Company LimitedQingyang745000China

The field data of shale fracturing demonstrate that the flowback performance of fracturing fluid is different from that of conventional reservoirs,where the flowback rate of shale fracturing fluid is lower than that of conventional *** the early stage of flowback,there is no single-phase flow of the liquid phase in shale,but rather a gas-water two-phase flow,such that the single-phase flow model for tight oil and gas reservoirs is not *** this study,pores and microfractures are extracted based on the experimental results of computed tomography(CT)scanning,and a spatial model of microfractures is ***,the influence of rough microfracture surfaces on the flow is corrected using the modified cubic law,which was modified by introducing the average deviation of the microfracture height as a roughness factor to consider the influence of microfracture surface *** flow in the fracture network is simulated using the modified cubic law and the lattice Boltzmann method(LBM).The results obtained demonstrate that most of the fracturing fluid is retained in the shale microfractures,which explains the low fracturing fluid flowback rate in shale hydraulic fracturing.

关键词： Shale Flowback of fracturing fluid Microfracture Lattice Boltzmann method(LBM)