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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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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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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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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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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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Methane adsorption on graphite(0001) films: A first-principles study

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Chinese Physics B 2013年第1期22卷 452-456页

作者：何满潮赵健 state key laboratory for Geomechanics and deep underground engineering China University of Mining and Technology

Using first-principles methods, we have systematically investigated the electronic density of states, work function, and adsorption energy of the methane molecule adsorbed on graphite（0001） films. The surface energy and the interlayer relaxation of the clean graphite（0001） as a function of the thickness of the film were also studied. The results show that the interlayer relaxation is small due to the weak interaction between the neighboring layers. The one-fold top site is found most favourable on substrate for methane with the adsorption energy of - 133 meV. For the adsorption with different adsorption heights above the graphite film with four layers, the methane is found to prefer to appear at about 3.21 A above the graphite. We also noted that the adsorption energy does not dependent much on the thickness of the graphite films. The work function is enhanced slightly by adsorption of methane due to the slight charge transfer from the graphite surface to the methane molecule.

关键词： first-principles calculations graphite methane molecule adsorption

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First-principles study of atomic and electronic structures of kaolinite in soft rock

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Chinese Physics B 2012年第3期21卷 530-533页

作者：何满潮赵健方志杰 state key laboratory for Geomechanics and deep underground engineering China University of Mining and Technology

Kaolinite is a kind of clay mineral which often causes large deformations in soft-rock tunnel engineering and thus causes safety issues. To deal with these engineering safety issues, the physical/chemical properties of the kaolinite should be studied from basic viewpoints. By using the density-functional theory, in this paper, the atomic and the electronic structures of the kaolinite are studied within the local-density approximation （LDA）. It is found that the kaolinite has a large indirect band gap with the conduction band minimum （CBM） and the valence band maximum （VBM） being at the F and the B points, respectively. The chemical bonding between the cation and the oxygen anion in kaolinite is mainly ionic, accompanied by a minor covalent component. It is pointed that the VBM and the CBM of kaolinite consist of oxygen 2p and cation s states, respectively. The bond lengths between different cations and anions, as well as of the different OH groups, are also compared.

关键词： kaolinite crystal structure first-principles method

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Seepage characteristics of collapse column fillings

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International Journal of Mining Science and Technology 2016年第2期26卷 333-338页

作者： Zhang Boyang Bai Haibo Zhang Kai state key laboratory of Geomechanics and deep underground engineering China University of Mining & Technology

With concealment and hysteresis,water-inrush from Karst collapse column has become an important security hazard of lower group coal mining in North *** on the MTS8 15.02 seepage test system,we analyzed the impact of consolidation pressure,initial moisture content and confining pressure on the permeability of fillings in order to study the seepage characteristics of collapse column *** results show that:(l)The permeability of collapse column fillings is of the order of 10^(-16)-10^(-15) magnitude and decreases with an increase in consolidation pressure and decrease in initial moisture content.(2) The essence of filling seepage law change is the change in porosity,and a power function relationship exists between the permeability ratio and porosity ratio.(3) With increasing confining pressure,the permeability of fillings ***,under low confining pressure(1.2-4 MPa),the change of confining pressure has no obvious influence on the permeability.

关键词： Collapse column Filings Porosity Consolidation Permeability Moisture content

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Triaxial compression strength for artificial frozen clay with thermal gradient

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Journal of Central South University 2013年第1期20卷 218-225页

作者：赵晓东周国庆陈国舟 state key laboratory for Geomechanics and deep underground engineering (China University of Mining and Technology)

A series of triaxial compression tests for frozen clay were performed by KoDCGF （freezing with non-uniform temperature under loading after K0 consolidation） method and GFC （freezing with non-uniform temperature without experiencing Ko consolidation） method at various confining pressures and thermal gradients. The experimental results indicate that the triaxial compression strength for frozen clay in KoDCGF test increases with the increase of confining pressure, but it decreases as the confining pressure increases further in GFC test. In other words, the compression strength for frozen clay with identical confining pressure decreases with the increase in thermal gradient both in KoDCGF test and GFC test. The strength of frozen clay in KoDCGF test is dependent of pore ice strength, soil particle strength and interaction between soil skeleton and pore ice. The decrease of water content and distance between soil particles leads to the decrease of pore size and the increase of contact area between particles in KoDCGF test, which further results in a higher compression strength than that in GFC test. The compression strength for frozen clay with thermal gradient can be descried by strength for frozen clay with a uniform temperature identical to the temperature at the height of specimen where the maximum tensile stress appears.

关键词： artificial frozen clay triaxial compression test thermal gradient strength

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Physical and mechanical properties of sandstone containing a single fissure after exposure to high temperatures

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International Journal of Mining Science and Technology 2016年第2期26卷 319-325页

作者： Zhu Tantan Jing Hongwen Su Haijian Yin Qian Du Mingrui Han Guansheng state key laboratory for Geomechanics & deep underground engineering China University of Mining & Technology

In order to investigate the physical and mechanical properties of sandstone containing fissures after exposure to high temperatures,fissures with different angles α were prefabricated in the plate sandstone samples,and the processed samples were then heated at 5 different *** uniaxial compression was conducted to analyze the change rules of physical properties of sandstone after exposure to high temperature,and the deformation,strength and failure characteristics of sandstone containing *** results show that,with increasing temperature,the volume of sandstone increases gradually while the quality and density decrease gradually,and the color of sandstone remains basically unchanged while the brightness increases markedly when the temperature is higher than 585 ℃;the peak strength of sandstone containing fissures first decreases then increases when the temperature is between 25℃and 400℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature,and the mechanical properties of sandstone show obvious deterioration after 400 ℃.The peak strain of sandstone containing fissures increases gradually while the average modulus decreases gradually with increasing temperature;with increasing angle αof the fissure,the evolution characteristics of the macro-mechanical parameters of sandstone are closely related to the their own mechanical *** the temperature is 800 ℃,the correlation between the peak strength and average modulus of sandstone and the angle α of the fissure is obviously *** failure modes of sandstone containing fissures after high temperature exposure are of three different kinds including:tensile crack failure,tensile and shear cracks mixed failure,and shear crack *** and shear crack mixed failure occur mainly at low temperatures and small angles;tensile crack failure occurs at high temperatures and large angles.

关键词： High temperature Sandstone containing fissure Strength characteristics Deformation characteristics Evolution law

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