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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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Effects of vertical seismic acceleration on 3D slope stability

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Earthquake engineering and engineering Vibration 2016年第3期15卷 487-494页

作者： Zhang Fei Gao Yufeng Wu Yongxin Zhang Ning Qiu Yue Key laboratory of Ministry of Education for geomechanics and Embankment engineering Hohai University

The conventional pseudo-static approach often neglects the effect of the vertical＇ seismic acceleration on the stability of a slope, but some analyses under plane-strain （2D） conditions show a significant effect on the slope stability. The purpose of this study is to investigate the effect of the vertical acceleration on the safety of three-dimensional （3D） slopes. In the strict framework of limit analysis, a 3D kinematically admissible rotational failure mechanism is adopted here for 3D homogeneous slopes in frictional/cohesive soils. A set of stability charts is presented in a wide range of parameters for 3D slopes under combined horizontal and vertical seismic loading conditions. Accounting for the effects of the vertical seismic acceleration, the difference in safety factors for 3D slopes can exceed 10%, which will significantly overestimate the safety of the 3D slopes.

关键词： slope stability seismic effects limit states three-dimensional analysis vertical acceleration

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Three-dimensional analysis of slopes reinforced with piles

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Journal of Central South University 2015年第6期22卷 2322-2327页

作者：高玉峰叶茂张飞 Key laboratory for geomechanics and Embankment engineering of Ministry of Education (Hohai University)

Based on the upper bound of limit analysis, the plane-strain analysis of the slopes reinforced with a row of piles to the 3D case was extended. A 3D rotational failure mechanism was adopted to yield the upper bound of the factor of safety. Parametric studies were carried out to explore the end effects of the slope failures and the effects of the pile location and diameter on the safety of the reinforced slopes. The results demonstrate that the end effects nearly have no effects on the most suitable location of the installed piles but have significant influence on the safety of the slopes. For a slope constrained to a narrow width, the slope becomes more stable owing to the contribution of the end effects. When the slope is reinforced with a row of piles in small space between piles, the effects of group piles are significant for evaluating the safety of slopes. The presented method is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of plies stabilizing the unstable slopes.

关键词： three-dimensional rotational failure mechanism stability of slopes limit analysis landslides piles

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Density functional theory investigation of carbon monoxide adsorption on the kaolinite(001) surface

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Chinese Physics B 2017年第7期26卷 495-500页

作者：赵健何满潮胡祥星高炜 State Key laboratory for geomechanics and Deep Underground engineering China University of Mining and Technology

Carbon monoxide（CO） is a gaseous pollutant with adverse effects on human health and the environment. Kaolinite is a natural mineral resource that can be used for different applications, including that it can also be used for retention of pollutant gases. The adsorption behavior of carbon monoxide molecules on the（001） surface of kaolinite was studied systematically by using density-functional theory and supercell models for a range coverage from 0.11 to 1.0 monolayers（ML）. The CO adsorbed on the three-fold hollow, two-fold bridge, and one-fold top sites of the kaolinite（001） was tilted with respect to the surface. The strongest adsorbed site of carbon monoxide on the kaolinite（001） surface is the hollow site followed by the bridge and top site. The adsorption energy of CO decreased when increasing the coverage, thus indicating the lower stability of surface adsorption due to the repulsion of neighboring CO molecules. In addition to the adsorption structures and energetics, the lattice relaxation, the electronic density of states, and the different charge distribution have been investigated for different surface coverages.

关键词： kaolinite adsorption carbon monoxide density functional theory

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Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

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Journal of Central South University 2015年第11期22卷 4434-4444页

作者：付强刘汉龙丁选明郑长杰 College of Civil and Transportation engineering Hohai University Key laboratory of Ministry of Education for geomechanics and Embankment engineering

A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic velo

关键词： finite element simulation track-ballast-embankment

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Journal of Central South University 2015年第8期22卷 3069-3078页

作者：倪小东王媛陈珂赵帅龙 Key laboratory of Ministry of Education for geomechanics and Embankment engineering College of Civil and Transportation Engineering Hohai University

Conventional model tests and centrifuge tests are frequently used to investigate seepage erosion. However, the centrifugal test method may not be efficient according to the results of hydraulic conductivity tests and piping erosion tests. The reason why seepage deformation in model tests may deviate from similarity was first discussed in this work. Then, the similarity criterion for seepage deformation in porous media was improved based on the extended Darcy-Brinkman-Forchheimer equation. Finally, the coupled particle flow code–computational fluid dynamics(PFC-CFD) model at the mesoscopic level was proposed to verify the derived similarity criterion. The proposed model maximizes its potential to simulate seepage erosion via the discrete element method and satisfy the similarity criterion by adjusting particle size. The numerical simulations achieved identical results with the prototype, thus indicating that the PFC-CFD model that satisfies the improved similarity criterion can accurately reproduce the processes of seepage erosion at the mesoscopic level.

关键词： mesoscopic model centrifugal model similarity criterion particle flow code-computational fluid dynamics (PFC-CFD)

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An experimental study on fracture mechanical behavior of rock-like materials containing two unparallel fissures under uniaxial compression

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Acta Mechanica Sinica 2016年第3期32卷 442-455页

作者： Yan-Hua Huang Sheng-Qi Yang Wen-Ling Tian Wei Zeng Li-Yuan Yu State Key laboratory for geomechanics and Deep Underground engineering China University of Mining and Technology

Strength and deformability characteristics of rock with pre-existing fissures are governed by cracking behavior. To further research the effects of pre-existing fissures on the mechanical properties and crack coalescence process, a series of uniaxial compression tests were carried out for rock-like material with two unparallel *** the present study, cement, quartz sand, and water were used to fabricate a kind of brittle rock-like material cylindrical model specimen. The mechanical properties of rock-like material specimen used in this research were all in good agreement with the brittle rock materials. Two unparallel fissures（a horizontal fissure and an inclined fissure） were created by inserting steel during molding the model *** all the pre-fissured rock-like specimens were tested under uniaxial compression by a rock mechanics servocontrolled testing system. The peak strength and Young＇s modulus of pre-fissured specimen all first decreased and then increased when the fissure angle increased from 0？to 75？.In order to investigate the crack initiation, propagation and coalescence process, photographic monitoring was adopted to capture images during the entire deformation ***, acoustic emission（AE） monitoring technique was also used to obtain the AE evolution characteristic of prefissured specimen. The relationship between axial stress, AE events, and the crack coalescence process was set up： when a new crack was initiated or a crack coalescence occurred, thecorresponding axial stress dropped in the axial stress–time curve and a big AE event could be observed ***, the mechanism of crack propagation under microscopic observation was discussed. These experimental results are expected to increase the understanding of the strength failure behavior and the cracking mechanism of rock containing unparallel fissures.

关键词： Rock-like material Two unparallel fissures Mechanical parameters Crack evolution Acoustic emission(AE)

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Macro and micro mechanics behavior of granite after heat treatment by cluster model in particle flow code

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Acta Mechanica Sinica 2018年第1期34卷 175-186页

作者： Wen-Ling Tian Sheng-Qi Yang Yan-Hua Huang State Key laboratory for geomechanics and Deep Underground engineering China University of Mining and Technology

In this paper, a cluster model in particle flow code was used to simulate granite specimens after heat treatment under uniaxial compression. The results demonstrated that micro-cracks are randomly distributed in the specimen when the temperature is below 300?C, and have partial coalescence when the temperature is up to 450?C, then form macro-cracks when the temperature is above 600?C. There is more inter-granular cracking than intra-granular cracking, and their ratio increases with increasing *** micro-cracks are almost constant when the temperature decreases from 900?C to room temperature, except for quartz α–β phase transition temperature(573?C). The fracture evolution process is obviously affected by these cracks, especially at 600–900?C. Elevated temperature leads to easily developed displacement between the grains, and the capacity to store strain energy becomes weaker, corresponding to the plasticity of granite after heat treatment.

关键词： Cluster model Granite Thermal damage Micro-crack Energy

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Effect of integrating memory on the performance of the fractional plasticity model for geomaterials

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Acta Mechanica Sinica 2018年第5期34卷 896-901页

作者： Yifei Sun Yufeng Gao Shunxiang Song Key laboratory of Ministry of Education for geomechanics and Embankment engineering Hohai UniversityNanjing 210098China

A fractional plasticity model for geomaterials is proposed by using the fractional *** to the integral definition of the fractional derivative,the range of load memory for calculating the flow direction may influence the subsequent model ***,an investigation on the memory dependence of the model was *** was found that the load memory affected the stress-dilatancy behavior of the *** to the loss of memory from zero-to confiningstress states,slightly higher strain is reported,whereas an insignificant difference in the predicted deviator stress is ***,for engineering applications,starting the memory from the zero-stress state,which avoids mathematical complexity,is suggested.

关键词： Plasticity Fractional calculus Memory

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Strength and deformation behaviors of veined marble specimens after vacuum heat treatment under conventional triaxial compression

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Acta Mechanica Sinica 2017年第5期33卷 886-898页

作者： Haijian Su Hongwen Jing Qian Yin Liyuan Yu Yingchao Wang Xingjie Wu State Key laboratory for geomechanics and Deep Underground engineering China University of Mining and Technology

The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal resource exploitation. In this paper, veined marble specimens were treated to high temperature treatment and then used in conventional triaxial compression tests to investigate the effect of temperature, confining pressure, and vein angle on strength and deformation behaviors. The results show that the strength and deformation parameters of the veined marble specimens changed with the temperature, presenting a critical temperature of 600 . The triaxial compression strength of a horizontal vein () is obviously larger than that of a vertical vein (). The triaxial compression strength, elasticity modulus, and secant modulus have an approximately linear relation to the confining pressure. Finally, Mohr-Coulomb and Hoek-Brown criteria were respectively used to analyze the effect of confining pressure on triaxial compression strength.

关键词： Veined marble Conventional triaxial compression High temperature Vein angle Hoek-Brown criterion

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