True triaxial test and failure criterion of coal gangue concrete

ZHAO Weiping; HE Yuxiang; JIANG Kongliang; YANG Jiaqi; XU Yang; CHEN Jialong

doi:10.13225/j.cnki.jccs.2024.1009

Abstract：In view of the pollution caused by the large storage of coal gangue and the shortage of natural aggregate in con-crete,using coal gangue as coarse aggregate is a reasonable way to solve the above problems.In order to reveal the mech-anical properties of coal gangue concrete and promote the application of coal gangue concrete in the field of civil engineer-ing,the mechanical response of coal gangue concrete under multiaxial stress state is studied.Three kinds of concrete mix ratios with coal gangue volume substitution rates of 0,30％and 50％were designed.225 specimens were prepared for true triaxial compression test of coal gangue concrete.A total of 20 true triaxial compressive stress ratios,including four min-imum principal stress ratios(σ1/σ3=0.05,0.08,0.13,and 0.16)and five Lode angles(θ=0°,15°,30°,45°,and 60°)were designed in the experiments.The failure modes,strength characteristics and triaxial compression strength improvement of concrete with different coal gangue replacement rates under different stress ratios were compared and analyzed,based on the triaxial compression test results of coal gangue concrete,a multi-axial strength failure criterion considering the replace-ment rate of coal gangue was established.The results show that the multiaxial failure modes present four types(Cylindric-al failure mode,Slice shape failure mode,Oblique shear failure mode,Extrusion fluid failure mode)with the change of stress ratio,and have little correlation with the replacement rate of coal gangue.With the increase of σ2/σ3,the compress-ive strength increases first and then decreases,and the maximum value is at θ=30°.Whenσ1/σ3is small,the effect of σ2/σ3 on the triaxial compressive strength is not obvious.The larger theσ1/σ3is,the more significant the effect of σ2/σ3 on the tri-axial compressive strength is.The higher the replacement rate of coal gangue,the lower the triaxial compressive strength,and the greater theσ1/σ3,the more obvious the strength decrease,whenσ1/σ3is small,there is little difference in the im-provement degree of triaxial compressive strength between coal gangue concrete and ordinary concrete.When σ1/σ3 is large,the improvement degree of strength of coal gangue concrete is significantly lower than that of ordinary concrete.The established failure criterion considering the replacement rate of coal gangue is well fitted with the triaxial compres-sion test results of concrete.It can correctly reflect the influence of coal gangue coarse aggregate on the multiaxial mech-anical properties of concrete,and can be used to predict the multiaxial strength of coal gangue concrete with different coal gangue replacement rates and different stress ratios.The research results can provide data reference for the practical engin-eering application of coal gangue concrete,in order to realize the solid waste utilization of coal gangue.