Research On Damage Evolution And Constitutive Relationship Of Shale Ceramsite Concrete

Compared with normal concrete of the same strength,the weight of lightweight shale ceramsite concrete(LWSCC)can be reduced by 20-25%,and LWSCC also has many advantages,such as stronger crack resistance,higher frost resistance,better deformation resistance,bigger energy absorption and stronger earthquake resistance,etc.LWSCC not only has excellent deformation resistance and energy consumption capacity for the support system in deep and soft rock roadway,but also has excellent comprehensive disaster resistance in low-temperature environments for freezing construction,high-temperature environments for mine fires and dynamic load conditions.The paper took all lightweight shale ceramsite concrete(ALWSCC)as the object of study.Through testing and theoretical analysis of ALWSCC under complex working conditions,the damage evolution rule from Macro-Microscopic perspective was revealed,the influence mechanism of high and cryogenic temperature was analyzed,and the damage constitutive relationship and damage criterion under quasi-static and dynamic-static coupled loading conditions was proposed.The main research contents are as follows:(1)The overlap effect at the interface transition zone was analyzed by using the volume calculation model of interface transition zone,and a volume fraction calculation method for the interface transition zone of concrete that satisfies the Fuller grading curve was given.Combining the Mori-Tanaka theory and the two-phase sphere theory,the micromechanical model of ALWSCC including shale ceramsite,shale pottery sand,interfacial transition zone and cement matrix was constructed.Based on the micro-micro characteristics and the distribution rule of the interface transition zone,the inversion method of meso parameters was put forward.Using experimental research and theoretical calculations,the effective elastic modulus of each mesophase was obtained,and the prediction model of effective elastic modulus considering the characteristics of aggregate gradation was constructed.(2)The parameter characteristics of acoustic emission signal for ALWSCC were analyzed through acoustic emission test.A nonlinear compaction component was proposed to describe the compaction process of pores in aggregate during quasi-static loading process.Combined with the elastic-brittle damage constitutive model,the damage constitutive relationship of ALWSCC subject to quasi-static compression was constructed.A three-dimension random aggregate model was established to reveal the damage evolution mechanism of ALWSCC subject to static load from the perspective of mesomechanics.(3)The strength rule of ALWSCC in the environment with the temperature range of 0 –-30 ℃ and 200 –600 ℃ was studied.The influence mechanism of cryogenic curing and the degradation mechanism after high temperature was analyzed,and the micro-micro damage evolution model after high temperature was established.(4)The failure mode and strain rate effect of ALWSCC subject to uniaxial SHPB impact were analyzed,and the dynamic constitutive relationship of elastic brittle damage was constructed.A meso-numerical model was established for the dynamic impact numerical simulation,revealing the damage evolution mechanism of ALWSCC subjected to dynamic impact.(5)By means of perimeter-constrained large-diameter SHPB test,the influence rule of axial and perimeter preload on stress wave was analyzed,as well as the variation rule of failure mode,peak stress,and energy dissipation.The spatial evolution characteristics of the pore-crack structure of ALWSCC specimens before and after impact were comparatively analyzed by industrial CT scans.Based on dynamic stress-strain curves,the dynamic impact strength criterion and the constitutive relationship under dynamic-static coupled loading conditions were established.The developed mesoscopic mechanic model and the proposed mesoscopic parameter inversion method in this paper are also applicable to similar concrete materials.The improved quasi-static constitutive model realizes the purpose of describing the global compaction process and the global damage process before the failure of ALWSCC.The improved dynamic damage constitutive model is more suitable for describing the stress-strain curve of materials subjected to dynamic and static coupled loading because its parameters have definite physical significance.The achievements in this paper provide the basis for testing and theoretical analysis of matrix materials for the application of engineering structures under complex conditions.There are 109 pictures,23 tables,159 references in this paper.