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Effects of aggregate size distribution and carbon nanotubes on the mechanical properties of cemented gangue backfill samples under true triaxial compression

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International Journal of Minerals,Metallurgy and Materials 2025年第2期32卷 311-324页

作者： Qian Yin Fan Wen Zhigang Tao Hai Pu Tianci Deng Yaoyao Meng Qingbin Meng Hongwen Jing Bo Meng Jiangyu Wu State key laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground engineering China University of Mining and TechnologyXuzhou 221116China State key laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines Anhui University of Science and TechnologyHuainan 232001China State key laboratory for geomechanics&Deep Underground engineering China University of Mining and Technology(Beijing)Beijing 100083China key laboratory of Xinjiang Coal Resources Green Mining Ministry of EducationXinjiang Institute of EngineeringUrumqi 830023China

The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious ***,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of *** mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically *** results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,***,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the ***σ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite ***ε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse *** increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.

关键词： cemented gangue backfill materials particle size distribution true triaxial compression test carbon nanotubes mechanical properties failure modes

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Stability analysis of cut-fill and deep patch unsaturated slopes under steady infiltration conditions

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Science China Technological Sciences 2025年第1期 356-367页

作者： Fei ZHANG Shilin JIA Yufeng GAO key laboratory of the Ministry of Education for geomechanics and Embankment engineering College of Civil and Transportation EngineeringHohai University

Cut-fill slopes, as an economical solution in mountainous road construction, are typically jeopardized by cracks and rainfall. Deep patch repair with geosynthetics is an effective technique to mitigate these issues. This paper proposes an upperbound analytical framework for evaluating the stability of cracked cut-fill slopes and deep patch slopes under one-dimensional steady infiltration. The proposed framework is employed to investigate suction-induced effects on slope stability and critical failure surface through a series of parametric analyses. The findings indicate that the suction-induced effect generally increases with air-entry pressure and approaches a constant value. The stability of a cracked cut-fill slope can be enhanced by deep patch repair with geosynthetics. Increasing the deep patch depth enhances local stability and reduces the required reinforcement strength. Generally, the depth of the deep patch should be greater than the crack depth to avoid local failures. Furthermore, a design method involving both local and global stability for deep patch slopes is presented, along with a design example for illustration.

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A general solution for vertical-drain consolidation with impeded drainage boundaries

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Journal of Central South University 2016年第4期23卷 934-943页

作者：付崔伟雷国辉 key laboratory of geomechanics and Embankment engineering of Ministry of Education Geotechnical Research Institute Hohai University

An analytical solution is derived from the generalized governing equations of equal-strain consolidation with vertical drains under multi-ramp surcharge preloading. The hydraulic boundary conditions at both top and bottom of the consolidating soil are modelled as impeded drainage. The impeded drainage is described by using the third type boundary condition with a characteristic factor of drainage efficiency. Fully drained and undrained boundary conditions can also be modelled by applying an infinite and a zero characteristic factor, respectively. Simultaneous radial and vertical flow conditions are considered, together with the effects of drain resistance and smear. An increase in total stress due to multi-ramp loading is reasonably modelled as a function of both time and depth. A solution to calculate excess pore-water pressure at any arbitrary point in soil is derived, and the overall average degree of consolidation is obtained. It shows that the proposed solution can be used to analyze not only vertical-drain consolidation but also one-dimensional consolidation under either one-way or two-way vertical drainage conditions. The characteristic factors of drainage efficiency of top and bottom boundaries have a potentially important influence on consolidation. The boundary may be considered fully drained when the characteristic factor is greater than 100 and fully undrained when the characteristic factor is less than 0.1. The stress distribution along depth induced by the surcharge loading has a limited effect on the overall average degree of consolidation.

关键词： consolidation vertical drain surcharge preloading drainage boundary condition multi-ramp loading

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Macro-micro investigation of granular materials in torsional shear test

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Journal of Central South University 2014年第7期21卷 2950-2961页

作者：李博郭林张丰收 Department of Civil engineering Wenzhou University guangxi key laboratory of geomechanics and geotechnical engineering Guilin University of Technology Itasca HoustonInc.

A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code *** wall technique boundary conditions are employed and optimized to reasonably capture the microstructure *** studies are conducted in terms of the ratio κ,normal and shear stiffness of particles,wall stiffness and friction ***,in comparison with physical test,numerical results for a fixed principal stress angle(α=45°) are *** results show that the numerical test could capture the macro-micro mechanical behavior of the spherical particle *** evolution of the coordination number demonstrates that particles in shear banding undergo remarkable *** effects of localization on specimens illustrate that global stress and strain recorded from a hollow cylinder apparatus could not represent the localized *** shearing band initiation and evolution from porosity and shear rate are visualized by contour lines in different shear strains.

关键词： hollow cylinder apparatus numerical modeling principal stress rotation strain localization

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Construction of a 3D meso-structure and analysis of mechanical properties for deposit body medium

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Journal of Central South University 2015年第1期22卷 270-279页

作者：石崇陈凯华徐卫亚张海龙王海礼王盛年 key laboratory of Ministry of Education for geomechanics and Embankment engineering(Hohai University) Institute of geotechnical engineering Hohai University

For deposit body medium, the internal structural properties may be the controlling factors for the strength of the material and the mechanical response. Based on the results of soil-rock meso-statistics using digital imaging, a simulated annealing algorithm is adopted to expand the meso-structural features of deposit bodies in 3D. The construction of the 3D meso-structure of a deposit body is achieved, and then the particle flow analysis program PFC3 D is used to simulate the mechanical properties of the deposit body. It is shown that with a combination of the simulated annealing algorithm and the statistical feature functions, the randomness and heterogeneity of the rock distribution in the 3D inner structure of deposit body medium can be realized, and the reconstructed structural features of the deposit medium can match the features of the digital images well. The spatial utilizations and the compacting effects of the body-centered cubic, hexagonal close and face-centered packing models are high, so these structures can be applied in the simulations of the deposit structures. However, the shear features of the deposit medium vary depending on the different model constructive modes. Rocks, which are the backbone of the deposit, are the factors that determine the shear strength and deformation modulus of the deposit body. The modeling method proposed is useful for the construction of 3D meso-scope models from 2D meso-scope statistics and can be used for studying the mechanical properties of mixed media, such as deposit bodies.

关键词： deposit body mesomechanical mode model continuation simulated annealing algorithm granular flow method

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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

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An examination of the mechanical interaction of drilling slurries at the soil-concrete contact

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2010年第4期11卷 294-304页

作者： Ressol R.SHAKIR key laboratory of MOE for geomechanics and Embankment engineering Hohai University geotechnical Research Institute Hohai University

Evidence gained from previous field tests conducted on drilled shaft foundation shows that using drilling slurries to stabilize a borehole during the construction may influence the interfacial shear *** paper deals with an exhaustive study of the effects of drilling slurries at the contact between soil and *** study involved adapting a simple shear apparatus and performing approximately 100 experimental tests on the interaction between two types of soils;clay and sandy clay and five specimens of concrete with different surface *** also involved using bentonite and polymer slurries as an interface layer between soil and *** showed that an interface layer of bentonite slurry between clay and concrete decreases the interfacial shear strength by 23% and as an interface layer between sandy clay and concrete,bentonite increases interfacial shear strength by 10%.Using polymer slurry as an interface layer between clay and concrete decreases the interfacial shear strength by 17% while using it as an interface layer between sandy clay and concrete increases the interfacial shear strength by 10%.Furthermore,the data show that using bentonite and polymer slurry as an interface layer between clay and concrete decreases the sliding ratio by 50% to 60%,while increasing the sliding ratio by 44% to 56% when these are used as an interface layer between sandy clay and concrete.

关键词： Drilled shaft foundation Drilling slurry Polymer Bentonite Simple shear test Concrete surface Soil structure interaction Mudcake

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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

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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

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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

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