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Early Cretaceous Tectonics and Evolution of the Tibetan Plateau

Acta Geologica Sinica(English Edition) 2016年第3期90卷 847-857页

作者： WU Zhenhan ZHAO Zhen Patrick J. BAROSH YE Peisheng Chinese Academy of Geological Sciences Beijing 100037 China P.J. Barosh andAssociates 103 Aaron Ave. Bristol RI 02809 USA institute of geomechanies Chinese Academy of Geological Sciences Beijing 100081 China

Selected geological data on Early Cretaceous strata, structures, magmatic plutons and volcanic rocks from the Kunlun to Himalaya Mountains reveal a new view of the Early Cretaceous paleo-tectonics and the related geodynamic movement of the Tibetan Plateau. Two major paleo- oceans, the Mid-Tethys Ocean between the Qiangtang and Lhasa blocks, and the Neo-Tethys Ocean between the Lhasa and Himalayan blocks, existed in the Tibetan region in the Early Cretaceous. The Himalayan Marginal and South Lhasa Seas formed in the southern and northern margins of the Neo- Tethys Ocean, the Central Tibet Sea and the Qiangtang Marginal Sea formed in the southern and northern margins of the Mid-Tethys Ocean, respectively. An arm of the sea extended into the southwestern Tarim basin in the Early Cretaceous. Early Cretaceous intensive thrusting, magmatic emplacement and volcanic eruptions occurred in the central and northern Lhasa Block, while strike- slip formed along the Hoh-Xil and South Kunlun Faults in the northern Tibetan region. Early Cretaceous tectonics together with magmatic K20 geochemistry indicate an Early Cretaceous southward subduction of the Mid-Tethys Oceanic Plate along the Bangoin-Nujiang Suture which was thrust ~87 km southward during the Late Cretaceous-Early Cenozoic. No intensive thrust and magmatic emplacement occurred in the Early Cretaceous in the Himalayan and southern Lhasa Blocks, indicating that the spreading Neo-Tethys Oceanic Plate had not been subducted in the Early Cretaceous. To the north, terrestrial basins of red-beds formed in the Hoh-Xil, Kunlun, Qilian and the northeastern Tarim blocks in Early Cretaceous, and the Qiangtang Marginal Sea disappeared after the Qiangtang Block uplifted in the late Early Cretaceous.

关键词： Early Cretaceous paleo-tectonics subduction of the oceanic plate K20 geochemistry of granites Bangoin-Nujiang Suture the Tibetan Plateau

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Application of a vertex chain operation algorithm on topological analysis of three-dimensional fractured rock masses

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Frontiers of Structural and Civil Engineering 2017年第2期11卷 187-208页

作者： Zixin ZHANG Jia WU Xin HUANG Department of Geotechnical Engineering School of Civil Engineering Tongji University Shanghai 200092 China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji University State Key Laboratory for geomechanies and Deep Underground Engineering Xuzhou 221008 China a shanghai Tunnel Engineering & Rail Transit Design and Research institute Shanghai 200235 China

Identifying the morphology of rock blocks is vital to accurate modelling of rock mass structures. This paper applies the concepts of directed edges and vertex chain operations which are typical for block tracing approach to block assembling approach to construct the structure of three-dimensional fractured rock masses. Polygon subtraction and union algorithms that rely merely on vertex chain operation are proposed, which allow a fast and convenient construction of complex faces/loops. Apart from its robustness in dealing with finite discontinuities and complex geometries, the advantages of the current methodology in tackling some challenging issues associated with the morphological analysis of rock blocks are addressed. In particular, the identification of complex blocks with interior voids such as cavity, pit and toms can be readily achieved based on the number and the type of loops. The improved morphology visualization approach can benefit the pre-processing stage when analyzing the stability of rock masses subject to various engineering impacts using the block theory and the discrete element method.

关键词： morphology block assembling vertex operation discontinuities

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A HYDRO-MECHANICAL-CHEMICAL COUPLING MODEL FOR GEOMATERIAL WITH BOTH MECHANICAL AND CHEMICAL DAMAGES CONSIDERED

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Acta Mechanica Solida Sinica 2012年第4期25卷 361-376页

作者： Dawei Hu Hui Zhou Qizhi Hu Jianfu Shao Xiating Feng Haibin Xiao State Key Laboratory of geomechanies and Geoteehnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China LML UMR8107CNRSUniversity of Lille IVilleneuve d'AscqFrance School of Civil Engineering and Architecture Hubei University of TechnologyWuhan 430068China Laneang River Hydropower Co. LtdKunming 650214China

A general framework of hydro-mechanical-chemical coupling model is proposed for geomaterial subjected to the dual effects of mechanical loading and chemical degradation. Mechanical damage due to microcracks in solid matrix and chemical damage induced by the increase of porosity due to dissolution of matrix minerals as well as their interactions are considered. A special model is proposed for sandstone. The reaction rate is formulated within the framework of mineral reaction kinetics and can thus take into account different dissolution mechanisms of three main mineral compositions under different pH values. The increase of porosity is physically defined by the dissolution of mineral composition and the chemical damage is related to the increase of porosity. The mechanical behavior is characterized by unified plastic damage and viscoplastic damage modeling. The effective stress is used for describing the effect of pore pressure. The elastic parameters and plastic evolution as well as viscoplastic evolution are dependent on chemical damage. The advection, which is coupled with mechanical damage and chemical damage, is considered as the dominant mechanism of mass transfer. The application of model proposed is from decoupled experiments to fully coupled experiment. The model offers a convenient approach to describing the hydro-mechanical-chemical coupled behavior of geomaterial.

关键词： hydro-mechanical-chemical coupling mechanical damage chemical damage sandstone chemical kinetics

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A study of the energy yield criterion of geomaterials

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Engineering Sciences 2010年第3期8卷 12-20,40页

作者： Gao Hong Zheng Yingren Feng Xiating Zeng Jing State Key Laboratory of geomechanies and C.eoteehnieal Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China Department of Civil Engineering Logistical Engineering University of PLA Chongqing 400041 China

The study results of the internal friction character of geomaterials conclude that the internal friction exists in mechanical elements all the time having a direction opposite to the shear stress,and the deformation failure mechanism of geomaterials greatly differs from that of metals. For metals,the failure results from shear stresses make the crystal structure slip; whereas for geomaterials,owing to its attribute of granular structures,their deformation follows the friction law,it is the co-action of shear stresses and perpendicular stresses that makes grains overcome the frictions between them,thus leading to the final failure of relative ***,on the basis of the cognition above,a triple shear energy criterion is proposed. Its corresponding Drucker-Prager criterion for geomaterials is also given. The new criterion can be rewritten to the Mohr-Coulomb criterion by neglecting the effect of the intermediate principal stress,and to the Mises criterion by not taking the internal friction angle into consideration. Then the studies of yield criteria commonly used are conducted systematically from the points of stress,strain and energy of geomaterials. The results show that no matter which expression form of stress,strain or energy is used for the yield criterion,the essence is the same and the triple shear energy yield criterion is the unified criterion of materials. Finally,the experimental verification is conducted in connection with the practical application of the triple shear energy yield criterion in an engineering project,and the calculation result shows that the Mohr-Coulomb criterion which only takes the single shear surface into account is more conservative than the energy criterion that does consider the effect of triple shear surfaces.

关键词：岩土材料屈服准则能量准则中间主应力效应作者能源系统统一标准摩擦特性

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An h-adaptive numerical manifold method for solid mechanics problems

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Science China(Technological Sciences) 2018年第6期61卷 923-933页

作者： YU ChangYi LIU Feng XU Ying State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil Engineering Tianjin University Tianjin 300072 China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China

The numerical manifold method(NMM) features its dual cover systems, namely the mathematical cover and physical cover,which provide a unified framework for mechanics problems involving continuum and discontinuum deformation. Uniform finite element meshes can be and are usually used to construct the mathematical cover. Though this strategy can handle different kinds of problems in a unified way, it is not economical for cases with steep deformation gradients or singularities. In this paper, using the recovery-based error estimator, an h-adaptive NMM on quadtree meshes is proposed to deal with such cases. The quadtree meshes serve as the mathematical meshes, on which the local refinement is carried out. When the quadtree meshes are refined,the corresponding mathematical cover, physical cover and manifold elements are updated accordingly. To handle the hanging nodes in the quadtree meshes, we resort to mean value coordinates. Comparing to the refinement based on manifold elements,the proposed strategy guarantees consistent structured meshes throughout the adaptive process, thus retaining the unique feature of original NMM. In contrast with polygonal finite element method, an advantage of the proposed method is that the meshes do not need to conform to the crack face and material boundary, which means the adaptive NMM is very suitable for problems with complex geometric boundary. Several representative mechanics problems, including crack problems, are analyzed to investigate the effectiveness of the proposed method. It is demonstrated that the proposed adaptive NMM has higher accuracy and better performance comparing to uniform refinement strategy.

关键词：力学问题歧管构造数学有限元素裂缝问题 NMM 统一方法适应过程

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GEOLOGICAL MODEL OF TECTONIC STRESS METAMORPHISM OF COAL

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Chinese Science Bulletin 1980年第6期25卷 493-496页

作者：缪奋 institute of Geological Prospecting Ministry of Coal Industry

Investigations of the actual disposition of metamorphic coal zones in the eastern part of China led to the problem of tectonic stress metamorphism of coal. It is a new pattern for coal metamorphosis developed in recent years by Chinese geologists through field practice guided by the prineiples of geomechanies. Their research work reveals that the orientation, extension and arrangement of disposition of metamorphic coal zones of the Late Palaeozoic and Mesozoic eras are usually related

关键词： metamorphic disposition Mesozoic tectonic eastern folding basement guided strata Permian

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