首页|Effects of aggregate size distribution and carbon nanotubes on the mechanical properties of cemented gangue backfill samples under true triaxial compression
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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The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(PCNT)that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The 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 ap-pears at PCNT of 0.08wt％.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σp),axial peak strain(εl,p),elastic strain energy(Ue),and dissipated energy(Ud)increased by 12.76％,29.60％,19.05％,and 90.39％,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease in σp,εl,p,and the volumetric strain increment(Δεv)when PCNT 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 aggregates.Theσp and Ud firstly increase and then decrease with increasing D,and porosity shows the opposite trend.The εl,p and Δεv are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(εl,p=0.05079,Δsv=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequen-tially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.
State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering,China University of Mining and Technology,Xuzhou 221116,China
State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines,Anhui University of Science and Technology,Huainan 232001,China
State Key Laboratory for Geomechanics & Deep Underground Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China
Key Laboratory of Xinjiang Coal Resources Green Mining,Ministry of Education,Xinjiang Institute of Engineering,Urumqi 830023,China
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