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Dynamic analysis of slab track on multi-layered transversely isotropic saturated soils subjected to train loads

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Earthquake Engineering and Engineering Vibration 2014年第4期13卷 731-740页

作者： Zhan Yongxiang Yao Hailin Lu Zheng Yu Dongming Institute of rock and Soil mechanics Chinese Academy of Sciences State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and soil Mechanics Chinese Academy of Sciences

The dynamic responses of a slab track on transversely isotropic saturated soils subjected to moving train loads are investigated by a semi-analytical approach. The track model is described as an upper Euler beam to simulate the rails and a lower Euler beam to model the slab. Rail pads between the rails and slab are represented by a continuous layer of springs and dashpots. A series of point loads are formulated to describe the moving train loads. The governing equations of track-ground systems are solved using the double Fourier transform, and the dynamic responses in the time domain are obtained by the inverse Fourier transform. The results show that a train load with high velocity will generate a larger response in transversely isotropic saturated soil than the lower velocity load, and special attention should be paid on the pore pressure in the vicinity of the ground surface. The anisotropic parameters of a surface soil layer will have greater influence on the displacement and excess pore water pressure than those of the subsoil layer. The traditional design method taking ground soil as homogeneous isotropic soil is unsafe for the case of RE 〈 1 and RG 〈 1, so a transversely isotropic foundation model is of great significance to the design for high train velocities.

关键词： slab track transversely isotropic saturated soil Biot's theory train load dynamic response

Simulation of failure process of jointed rock

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Journal of Central South University of Technology 2008年第6期15卷 888-894页

作者：张秀丽焦玉勇赵坚 State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences Ecole Polytechnique Federale de Lausanne Rock Mechanics Laboratory

A modified discontinuous deformation analysis (DDA) algorithm was proposed to simulate the failure behavior of jointed rock. In the proposed algorithm, by using the Monte-Carlo technique, random joint network was generated in the domain of interest. Based on the joint network, the triangular DDA block system was automatically generated by adopting the advanced front method. In the process of generating blocks, numerous artificial joints came into being, and once the stress states at some artificial joints satisfy the failure criterion given beforehand, artificial joints will turn into real joints. In this way, the whole fragmentation process of rock mass can be replicated. The algorithm logic was described in detail, and several numerical examples were carried out to obtain some insight into the failure behavior of rock mass containing random joints. From the numerical results, it can be found that the crack initiates from the crack tip, the growth direction of the crack depends upon the loading and constraint conditions, and the proposed method can reproduce some complicated phenomena in the whole process of rock failure.

关键词： discontinuous deformation analysis jointed rock rock failure Monte-Carlo technique random joint network advancing front method triangular block system

Bandgap characteristics analysis and graded design of a novel metamaterial for flexural wave suppression

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Applied Mathematics and mechanics(English Edition) 2025年第01期 1-24页

作者： Fan YANG Zhaoyang MA Xingming GUO Shanghai Key laboratory of mechanics in Energy Engineering Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai University Shanghai Institute of Aircraft mechanics and Control

A novel elastic metamaterial is proposed with the aim of achieving lowfrequency broad bandgaps and bandgap regulation. The band structure of the proposed metamaterial is calculated based on the Floquet-Bloch theorem, and the boundary modes of each bandgap are analyzed to understand the effects of each component of the unit cell on the bandgap formation. It is found that the metamaterials with a low elastic modulus of ligaments can generate flexural wave bandgaps below 300 Hz. Multi-frequency vibrations can be suppressed through the selective manipulation of bandgaps. The dual-graded design of metamaterials that can significantly improve the bandgap width is proposed based on parametric studies. A new way that can regulate the bandgap is revealed by studying the graded elastic modulus in the substrate. The results demonstrate that the nonlinear gradient of the elastic modulus in the substrate offers better bandgap performance. Based on these analyses, the proposed elastic metamaterials can pave the way for multi-frequency vibration control, low-frequency bandgap broadening, and bandgap tuning.

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A continuous-discontinuous cellular automaton method for cracks growth and coalescence in brittle material

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Acta Mechanica Sinica 2014年第1期30卷 73-83页

作者： Fei Yan Xia-Ting Feng Peng-Zhi Pan Shao-Jun Li State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Science

A method of continuous-discontinuous cellular automaton for modeling the growth and coalescence of multiple cracks in brittle material is presented. The method uses the level set to track arbitrary discontinuities, and calculation grids are independent of the discontinuities and no remeshing are required with the crack growing. Based on Grif- fith fracture theory and Mohr-Coulumb criterion, a mixed fracture criterion for multiple cracks growth in brittle mate- rial is proposed. The method treats the junction and coales- cence of multiple cracks, and junction criterion and coales- cence criterion for brittle material are given, too. Besides, in order to overcome the tracking error in the level set ap- proximation for crack junction and coalescence, a dichotomy searching algorithm is proposed. Introduced the above the- ories into continuous-discontinuous cellular automaton, the present method can be applied to solving multiple crack growth in brittle material, and only cell stiffness is needed and no assembled global stiffness is needed. Some numerical examples are given to shown that the present method is efficient and accurate for crack junction, coalescence and percolation problems.

关键词： Continuous-discontinuous cellular automatonmethod Multiple crack growth Discontinuous cellular au-tomaton Junction criterion - Coalescence criterion

rock INITIATION AND PROPAGATION SIMULATION UNDER COMPRESSION-SHEAR LOADING USING CONTINUOUS-DISCONTINUOUS CELLULAR AUTOMATON METHOD

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Acta Mechanica Solida Sinica 2015年第4期28卷 384-399页

作者： Fei Yan Xiating Feng Pengzhi Pan Shao jun Li State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

A continuous-discontinuous cellular automaton method is developed for rock initiation and propagation simulations, in which the level set method, discontinuous enrichment shape functions and discontinuous cellular automaton are combined. No renmshing is needed for crack growth analysis, and all calculations are restricted to cells without an assembled global stiffness matrix. The frictional contact theory is employed to construct the contact model of normal pressure and tangential shear on crack surfaces. A discontinuous cellular automaton updating rule suitable for frictional contact of rock is proposed simultaneously with Newton＇s iteration method for nonlinear iteration. Besides, a comprehensive fracturing criterion for brittle rock under compression-shear loading is developed. The accuracy and effectivenesss of the proposed method is proved by numerical simulation.

关键词： continuous-discontinuous cellular automaton method rock fracturing process compressionshear loading frictional contact comprehensive fracturing criterion

Modeling rock specimens through 3D printing: Tentative experiments and prospects

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Acta Mechanica Sinica 2016年第1期32卷 101-111页

作者： Quan Jiang Xiating Feng Lvbo Song Yahua Gong Hong Zheng Jie Cui State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

Current developments in 3D printing （3DP） technology provide the opportunity to produce rock-like specimens and geotechnical models through additive man- ufacturing, that is, from a file viewed with a computer to a real object. This study investigated the serviceability of 3DP products as substitutes for rock specimens and rock-type materials in experimental analysis of deformation and failure in the laboratory. These experiments were performed on two types of materials as follows：（1） compressive experiments on printed sand-powder specimens in different shapes and structures, including intact cylinders, cylinders with small holes, and cuboids with pre-existing cracks, and （2） com- pressive and shearing experiments on printed polylactic acid cylinders and molded shearing blocks. These tentative tests for 3DP technology have exposed its advantages in produc- ing complicated specimens with special external forms and internal structures, the mechanical similarity of its product to rock-type material in terms of deformation and failure, and its precision in mapping shapes from the original body to the trial sample （such as a natural rock joint）. These experiments and analyses also successfully demonstrate the potential and prospects of 3DP technology to assist in the deformation and failure analysis of rock-type materials, as well as in the sim- ulation of similar material modeling experiments.

关键词： rock mechanics Similar material 3Dprinting Geotechnical model Deformation and failure

Numerical manifold method based on isogeometric analysis

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Science China(Technological Sciences) 2015年第9期58卷 1520-1532页

作者： ZHANG YouLiang LIU DengXue TAN Fei State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences

In this study, numerical manifold method(NMM) coupled with non-uniform rational B-splines(NURBS) and T-splines in the context of isogeometric analysis is proposed to allow for the treatments of complex geometries and local refinement. Computational formula for a 9-node NMM based on quadratic B-splines is derived. In order to exactly represent some common free-form shapes such as circles, arcs, and ellipsoids, quadratic non-uniform rational B-splines(NURBS) are introduced into NMM. The coordinate transformation based on the basis function of NURBS is established to enable exact integration for the manifold elements containing those shapes. For the case of crack propagation problems where singular fields around crack tips exist, local refinement technique by the application of T-spline discretizations is incorporated into NMM, which facilitates a truly local refinement without extending the entire row of control points. A local refinement strategy for the 4-node mathematical cover mesh based on T-splines and Lagrange interpolation polynomial is proposed. Results from numerical examples show that the 9-node NMM based on NURBS has higher accuracies. The coordinate transformation based on the NURBS basis function improves the accuracy of NMM by exact integration. The local mesh refinement using T-splines reduces the number of degrees of freedom while maintaining calculation accuracy at the same time.

关键词： numerical manifold method (NMM) isogeometric analysis local refinement mathematical cover

Equivalent elastic compliance tensor for rock mass with multiple persistent joint sets:Exact derivation via modified crack tensor

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Journal of Central South University 2016年第6期23卷 1486-1507页

作者：崔洁江权冯夏庭李邵军高红李帅军 State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of Sciences

Discontinuities constitute an integral part of rock mass and inherently affect its anisotropic deformation *** work focuses on the equivalent elastic deformation of rock mass with multiple persistent joint sets.A new method based on the space geometric and mechanical properties of the modified crack tensor is proposed,providing an analytical solution for the equivalent elastic compliance tensor of rock mass.A series of experiments validate the capability of the compliance tensor to accurately represent the deformation of rock mass with multiple persistent joint sets,based on conditions set by the basic *** spatially varying rules of the equivalent elastic parameters of rock mass with a single joint set are analyzed to reveal the universal law of the stratified rock mass.

关键词： equivalent elastic compliance tensor crack tensor multiple joint sets rock mass

Optimizing profile line interval for enhanced accuracy in rock joint morphology and shear strength assessments

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International Journal of Mining Science and Technology 2024年第5期34卷 587-608页

作者： Leibo Song Quan Jiang Shigui Du Jiamin Song Gang Wang Yanting Gu Xingkai Wang Jinzhong Wu School of Civil Engineering Shaoxing UniversityShaoxing 312000China Key laboratory of rock mechanics and Geohazards of Zhejiang Province Shaoxing UniversityShaoxing 312000China State Key laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China Institute of rock mechanics Ningbo UniversityNingbo 315211China

2D profile lines play a critical role in cost-effectively evaluating rock joint properties and shear ***, the interval(ΔI_(L)) between these lines significantly impacts roughness and shear strength assessments. A detailed study of 45 joint samples using four statistical measures across 500 different ΔI_(L)values identified a clear line interval effect with two stages: stable and *** statistical analysis showed a linear relationship between the error bounds of four parameters,shear strength evaluation, and their corresponding maximum ΔI_(L)values, where the gradient k of this linear relationship was influenced by the basic friction angle and normal stress. Accounting for these factors,lower-limit linear models were employed to determine the optimal ΔI_(L)values that met error tolerances(1%–10%) for all metrics and shear strength. The study also explored the consistent size effect on joints regardless of ΔI_(L)changes, revealing three types of size effects based on morphological ***, larger joints required generally higher ΔI_(L)to maintain the predefined error limits, suggesting an increased interval for large joint analyses. Consequently, this research provides a basis for determining the optimal ΔI_(L), improving accuracy in 2D profile line assessments of joint characteristics.

关键词： rock joint Roughness Shear strength Size effect Profile line interval effect