Study On The Instantaneous And Rheological Mechanical Properties And Constitutive Model Of Marble

Through the conventional uniaxial compression tests in various stress loading rates andthe uniaxial creep tests in distinct initial stress of marble, this paper studied the instantaneousand rheological mechanical properties. Based on this, the instantaneous constitutive modelconsidering the stress loading rates and the rheological constitutive models were investigatedas well.In instantaneous mechanics part,5level’s stress loading rate was applied, and uniaxialcompression tests in various stress loading rate on the marble were carried out. Thecharacteristics of deformation, strength, failure and energy exchange were investigated as well.The results demonstrate that the strength characteristics of marble enhanced in line with theincrease of stress loading rate. With the increase of stress loading rate, the modulus ofdeformation, strength and brittleness increased. Accordingly, the statistical damage mechanicsand BP neural network technique were applied to establish instantaneous constitutive modelsbased on the influence of stress loading rate. These two models possess their individual merits.The statistical damage model could not only take the influence of stress loading rate intoaccount, but also describe the mechanics of deformation of marble in the process of damage.Then, the BP neural network exhibits rapid modeling trait and better engineeringpracticability.In the study of rheological mechanics of marble, the uniaxial grading loading creep testwas firstly designed and applied in various initial stresses loading rate, with same increase ofstress loading rate as well as fixed single stage duration. The creep curve reflects thenonlinear rheological characteristics of marble due to its friability. By deep analysis ofrheological curve, four deformation models of marble were reached, and then certain conceptswere proposed, like “accelerating critical stress rage”,“negative creep” and “critical stress inconstant speed”. In the analyses of creep deformation rate characteristics, long termcalculation and characteristics and failure characteristics, a conclusion was reached on theinfluence of distinct initial stress loading rate to its transformation and deformation. Then, theanalyses of the microcosmic patterns of facture and the distributions of cracks demonstratedthe marble creep rupture abide to the development pattern, that is, the loading damage of initial cracks——sample interior incompatible deformation——damageintensifying——crack growth expanding——macro view of splitting accompanied with shearfailure. Further, due to the mathematical advantage of fractional calculus, the rheologicalmodel of marble was established and then applied to damage mechanics and nonlinear viscoustheory with amelioration. Therefore, the variable element creep damage model was obtained,which could reflect the nonlinear rheological characteristics of marble. Two nonlinear viscouscomponents were proposed according to its characteristics in accelerating creep stage. Incombination with fractional calculus component, two four-component models were obtained,which could reflect the whole rheological characteristics of marble. Based on the practicalprinciples of rheological constitutive model, this paper started with ameliorating one sort ofelastic-plastic body components, in combination with fractional calculus component, and thenestablished novel, utility and laconic three-component models. It has been proved that thesemodels showed relatively good simulation precision and generalization performance. Finally,owing to the development advantage, the support vector machine was introduced to studyrock rheological constitutive model. A rheological model was established according to thesupport vector machine in respective loading. And it has been proved that this modelexhibited relatively high simulation precision and rapid application feature.